Hello, Antony Chadwick from the webinar vets, welcoming you to our next afternoon lunchtime webinar, and I'm so pleased and and so thankful for Nationwide for making this a free webinar for so many hundreds of vets and nurses. So thank you so much nationwide for making that possible. We're very fortunate today, and I know Stacey is getting her slides up as we speak, so we will be moving over to the .

Slide show in a minute. Stacey is going to be talking about hypercalcemia in dogs and cats and overview. Stacey's really well qualified to talk about this because she is a senior veterinary clinical pathologist at Nationwide Laboratories.

Stacey is a vet, she qualified from Bristol, and then did an equine residency and PhD at Lee Hurst, which is at Liverpool. Vet school and was tutored and looked after by Derek Nottenbelt, who, of course, is a very famous equine vet as well. And her PhD was on head shaking, which I'm sure any of you who are equine vets will know, is a very troubling and difficult area to diagnose.

Stacey is a fellow of the Royal College of Pathologists and has published papers, certainly mostly in the, in the equine field and also spoken at the very prestigious British Equine Veterinary Association Congress. I'm thrilled to have, Stacey on. I'm sure we're gonna have a great presentation, .

Endocrine diseases have always been an interest of mine, so I'm gonna sit back, take it easy and enjoy the webinar. So, Stacey, over to you. OK, thank you, Anthony, and good afternoon, everybody.

Today, I'm going to talk about hypercalcemia in dogs and cats. That'll be why. Sorry, excuse me.

So just as a brief introduction, I'm going to focus mainly on the ETopathogenesis and then talk about diagnosis. And then clinic, well, clinic in that order, as we've got in an introduction, but focused mainly on the ET pathogenes and diagnosis. And then go through a few clinical signs, etc.

And then talk about treatment right at the end. Now, the treatment, I don't really have any current experience of just what we know from textbooks, references, other clinicians. So that will just be, Sort of a summary of that.

So to start off with, with respect to calcium. Just going to run you through exactly what calcium is composed of. So the total calcium that you measure in blood, so the total serum or occasionally plasma calcium is made of 3 different parts.

The main part, which is about 50 to 55% is ionised calcium, and that's the active part, and this is the part that we need to look at. The other two parts, which one is the protein bounding, bound one, which is mainly albumin. And the complex calcium, which is complex to other sort of ions like phosphates, lactates, carbonates.

Form up less than half and are not important with respect to the calcium levels in the body. So in the dog and the cat, the ranges for total calcium and ionised calcium are fairly similar, and they're quite tight. The cats have a slightly lower bottom normal range, and the dogs are narrow range for the ionised calcium.

So in the lab, total calcium is usually measured by spectrophotometric methods, usually stum, but you can do it on plasma. And just to remind you, you need to avoid using the anticoagulant tubes, so EDTA, citrate, etc. Because they will chelate the calcium and therefore, you, you end up with a low result.

And it's often a low calcium, it's often an indication that you've got EDT contamination, EDTA sorry, contamination of the sample. So we need to avoid that, so serum, preferably. And then ionised calcium, you can actually, there are machines obviously in-house that can do this and the blood gas machines are one of the ones that does, that does do this and, and they measured by an iron-specific electrode.

The sample collection ionised calcium is different. We don't want gel tubes because this can contain calcium. And also, it needs to be collected anaerobically and preferably separated rather than left as whole blood.

We do have correction equations with respect to changes in pH, which will alter the the ionised calcium. So it's separated serum excluding air, and it doesn't need to be frozen because in some cases, if you do freeze it, it will actually artificially lower the ionised calcium. You can keep it at room temperature to chilled for quite a long time without it deteriorating.

So going on to pathogenesis, the, I'm just going to go through calcium regulation and just, you know, go through the actual hormones that are involved and then how we end up with this state of hypercalcemia. So the main hormones involved with calcium regulation are the parathyroid hormone, which is the main one. And we had the dog, in particular, has two sets of, or two pairs in the neck, which are quite tiny and they sit in the thyroid gland.

And they are responsible for the minute to minute control of the calcium. They've the bone and the kidneys to increase calcium. The next important one is calcitriol or vitamin D3.

And this is the active form of it is, is, at the kidney. So it's, it's effect is on the day to day control, so it's more longer term control of the calcium. And it is activating the kidneys and in dogs in particular, and cats, the liver can store vitamin D, and this is in the non-active form, and then it goes to the kidneys to be activated.

Calcitrol or vitamin D3 affects three different sites. It affects the intestine as well as the bone and the kidneys to increase the levels of ionised calcium. The calcitonin I've mentioned at the bottom there is not particularly important in our animals, so we don't tend to, to look at it or refer to it.

And the diagram on the side is just a, a sort of like illustration looking at PTH and showing the three main sites there that we've got. We've got kidney, bone, and intestine. So just a diagram, the parathyroid is labelled there as a tiny gland on each side, and it sits in the thyroid gland.

And it's obviously one of the things that could be at risk of being removed if you're doing surgery for hyperthyroidism in a cat and therefore a risk of post-op low calcium. So primarily, hypercalcium, hypercalcemia results due to either an increased bone mobilisation of calcium. Or decreased urinary calcium loss.

Now, I've put the increased intestinal calcium absorption as in a smaller font there because it, it does have variable contribution, and it is mainly the other two that result in the, the pathogenesis, of the hypercalcemia. But obviously, if you get vitamin D toxicity, then that sort of, that source is obviously a much greater contributor. So hypercalcemia, by definition.

Though total calcium is usually increased, total calcium is an insensitive method as indicated before, due to the fact that the ionised calcium is the fat, is the part that we're looking at, and that's the active part. So by definition, if you get a high dose of calcium, you should really confirm it with ionised calcium. So hypercalcemia, high, ionised calcium, and with the state of hypercalcemia, What, what should happen is you get decreased PTH or parathyroid secretion from the parathyroid gland and you get decreased calcitriol or vitamin D production or activation, I should say from the kidneys, and therefore it should result in an increased urinary calcium excretion.

And also decreased mobilisation of calcium from the bone. So the diagram here, I don't know if you can, yeah, you can see the top bit. So this is just to show the, the negative feedback.

In the, in the normal animal that has a functioning parathyroid gland, the, The parathyroid, is negatively, there's a negative feedback effect of it by calcium and phosphorus. So if you increase calcium and phosphorus, this has a negative feedback on the parathyroid gland and therefore decreased production of parathyroid hormone. The calcium and phosphorus also has a negative feedback on the kidneys and the activation to the active form of vitamin D3.

And there, it just shows vitamin D3 have an effect on the, has an effect on the bone and the intestines, as well as the, kidney. So just to go through a bit about vitamin D. I was, I was looking in this and I looking at this and I thought, oh, vitamin D, yeah, vitamin D3, that's just, you know, vitamin D.

But vitamin D is a group of compounds and there's not just vitamin D3. The two most important ones, well, vitamin D3 is the most important and then the next important is vitamin D2. And these two are important with respect to possible pathogenesis of hypercalcemia in our animals.

Now, unlike humans, dogs and cats have a limited or no ability to synthesise vitamin D in the skin, and they're sort of quite similar to us in our country where we get sun. Not a lot of the time, and therefore require vitamin D from another source, usually orally. So the two main sources of vitamin D, D2 and D3, so holy calciphol, which is vitamin D3.

This is found mainly in animal products. And then we've got ergocalci calcipherol, vitamin D2, which is usually a plant origin. Now, cats and dogs have different diets and therefore, dogs, which are omnivores, can deal with both of these vitamin D's.

So if they consume both of these, they can metabolise and activate both of them. The cats, unfortunately, are carnivores and therefore, they can only utilise vitamin D3. So if for some reason you were supplementing a cat, For whatever reason, though it's usually, it's probably unusual with vitamin D2, it probably would have minimal effect on the actual calcium levels.

Both those two, vitamin D2 and D3, sorry, they are converted in the liver to this non-active form of D3, which we can actually measure, which is called calcidiol, another name for vitamin, another different name to. So I think we just call it active and inactive D3. So just a diagram to show that there's a, there's the D3 choliccalciferols actually inactive, and then it requires a hydroxylation process, which occurs in the kidney to form the active form of it, which is 125 dihydroxy vitamin D3.

And the, the, in the humans, where it comes from the skin, it is actually, again, it forms the inactive form prior to being activated. So just to, there was just a brief table there so you could compare them, but D2 tends to be plant origin and D3 is the main one that we use for supplementations, particularly in humans as well. So just to go through, vitamin D is metabolised in the liver to the 25 hydroxy vitamin D, which is calcidol, and then this goes to the kidneys and becomes hydroxyized to, which is the form of vitamin D.

This then results in the three processes there to a varying degree. The hydroxy enzyme as I sort of alluded to previously, is also controlled by PTH to a degree and also the levels of calcium and phosphorus as to its activation. So you'll get an increased level of hydroxylation and vitamin D with increased PTH, and you'll get a decrease if we have high phosphorus for some reason or other, particularly, say, in kidney disease.

So, coming to hypercalcemia, the, there are two groups of causes which are named either primary hyperparathyroidism. Or secondary hyperparathyroidism, or they name them also PTH dependent, which is the primary hyperparathyroidism, or parathyroid or PTH independent hypercalcemia or hyperparathyroidism. So there's all long, long names.

So basically, we have a primary and we have a secondary, causes of the hypercalcemia. The primary hyperparathyroidism is an abnormality of the parathyroid gland. It's usually unilateral and most commonly, it's an adenoma involving one of the thyroid, sorry, parathyroid glands.

Occasionally, you'll get hyperplasia and less commonly, you'll get a carcinoma. It causes an overproduction of parathyroid hormone, which is not negatively, fed back by the calcium levels that it increases. So, though the calcium levels are increased because the PTH has increased, They don't have a negative feedback effect on the parathyroid gland because it's abnormal.

Now, in unilateral cases, the normal gland will obviously have a normal function and negative feedback and therefore, it will often become very tiny and the big, you know, the abnormal gland remain large or bigger. So, in these cases, we have a high parathyroid hormone level, and we have a high ionised calcium. In secondary hyperparathyroidism or parathyroid-independent hypercalcemia cases, there are lots of different processes that, that can result in this.

And one of them is to mimic the PTH and form these parathyroid-related proteins. And there are also interleukins, and things like tumour necrosis factor, various cytokines which are produced that can affect vitamin D and therefore affect calcium. So, in some of the cases, obviously, we have excess vitamin D causing hypercalcemia and that's a direct effect of the vitamin D.

The, in these cases, the ionised calcium is high and the PTH because it's been negatively affected by the high calcium is low or very low. Now, in occasional cases, we'll get PTH, which is in not low, as in not low, low, but in actually in our reference interval that we have. Now, when we look at these cases, it needs to be in the lower third of the reference range for the PTH for us to say that this is not a primary hyperparathyroid case, which sounds a bit sort of very close cut, but that's, that's how it works.

So there are transient causes of hypercalcemia, which may result in a high total calcium, but the ionised calcium is not affected, and this may include Things like dehydration, you get a sick animal that comes in dehydrated or it's got hyperproteinemia, etc. The increase in albumin and protein levels and that can cause increased binding to that and therefore resulting in an increased total calcium. And then I put on the the hypogenalum, which actually Does seem to be one of the more common causes of, of increased calcium.

And some of these, about 50% of a high dose of calcium, but only about a quarter will actually have a high ionised calcium if measured. And then there's some non-pathologic causes, particularly, remember, young animals may have higher calcium. And then there's the lab error.

You need to try and rule that out. I do know for a fact that if we do get significant hemolysis in some of the samples in the lab, our actual assay is affected rather than increasing calcium, it tends to lower the total calcium to a slight degree. So we need to rule out any spurious or lab errors.

So, just going, now going on to the actual causes in a bit more detail. So primary hyperparathyroidism is our, our primary cases and the PTH dependent. And then we've got these independent cases, which are not related to a high PTH and have other mechanisms.

And neoplasia is probably the most common. And then we've got various other causes include Addison's renal disease, usually chronic kidney disease and idiopathic, quite common in the cats. So this picture of an anal sac adenocarcinoma, which can result in hypercalcemia.

So, in order of most common neoplasia by far is the most common of the PTH independent types, hypercalcemia. And then in the dog, we've also got Addison's and then we have primary, which is less common, and renal failure, which, as I say, in most cases in renal failure and in, in acute, sorry, in chronic renal failure, it was actually the total calcium that's high and not the ionised calcium, but there are some cases where the ionised calcium does increase. So less common causes, just listed a few here.

But there's also things like, local osteolysis from infections, and mediated disease. There's also, overdosing if you've been using calcium, containing phosphate binders, say, for in treatment of chronic kidney disease. And also occasionally there's reports of grape or raising toxicity, which in most of these cases actually by the time they're found, they've actually consumed quite a lot of this and the result is quite severe disease or even fatal.

So it, it's not common, but it does occur. So just a bit more detail on neoplasia. This, as I've said before, it's an independent PTH independent hypercalcemia.

There's a high ionised calcium, and there's usually low or low normal PTH. Now, PTHRP we can measure that, and that has increased in some of the cases, but not all. It's often, high with, or in in most cases, I said, would say anal sac, adenocarcinomas, but also lymphoma.

And then there are other sort of hematologic type malignancies like multiple myeloma that can result in high calcium and metastatic tumours to the, to the bone. In cases of malignancy, it's usually the hemoal causes that are resulting in this high calcium, and one of them is to mimic the PTHRP and some of the tumours actually secrete a similar protein which can be measured, which is we call PTHRP, and this has the same effect as PTH on the receptors to increasing calcium in the, the kidneys and bone. There are also cytokines which I mentioned before, which can have, similar effects, particularly in activating or making vitamin D and therefore affecting calcium.

So in lymphoma, probably about The 3rd round about that will have hypercalcemia and they're usually associated with a T cell type lymphoma. Anal sac adenocarcinoma, as I mentioned, they often show hypercalcemia. So, as I say, look at this, only 50%, in the references that I've found actually demonstrated.

So there are cases that you can have that and they will not have the, coexisting hypercalcemia. The other neoplasmins I've mentioned before, and they do include things like carcinomas and melanomas, they can be, they can result in high calcium. So the local osteolytic effect, as I say, it tends to be more the metastatic tumours that cause this.

It's very rarely that you'll see primary bone tumours resulting in a hypercalcemia. So, you know, if you have an osteosarcoma, it's unlikely to, if you go and measure calcium in those cases for that to be high. So it's mainly, as I say, metastatic, causing the local effects with releasing calcium from the bone.

And then we've got Addison's, which I've mentioned. It does tend to be quite mild and obviously, it's reversed when you have adequate treatment and of the, of the Addison's itself. The chronic kidney disease in most cases have a normal or low ionised calcium.

And it's the total calcium that's elevated. And then I'll come on to it, but I've mentioned at the bottom, I, I'm sorry, on some of these slides, there is quite a lot of details. So don't, don't worry about, you know, trying to copy them.

I, you can have a copy of the slides if you would wish. But there, in chronic kidney disease, you can get a form of tertiary hyperparathyroidism which becomes more complicated, and the exact cause is not completely, understood. So in chronic kidney disease, just a bit more detail, you can actually get hypercalcemia secondary to the treatment of it, as I alluded to before, with respect to, if you're using calcitriol for some reason, or you've got these, phosphate binders that contain calcium, and this can result in increased calcium.

However, if the treatment is monitored and everything, this should really be, not happen that, that commonly. And usually you can, you can use them at quite low doses with reasonable effect. The tertiary hyperparathyroidism is usually the result of these chronic kidney cases going through a stage where the low or low, sorry, the normal or low calcium, ionised calcium causes an increase in PTH and then Combined with the uremic toxins, you get altering and decreasing the number of the actual receptors in the PTH for the calcium and And also it affects the vitamin D activation with when you have renal, you know, tubular disease, and we end up with this low calcium affecting a high, causing a high PTH which then for some reason sets the calcium, it increases the calcium and then sets the calcium level in which is normally set by the hypothalamus, hypothalamus at a higher level and therefore it thinks that this higher level of calcium is normal and therefore these cats, these cats and dogs become.

Hypercalcemic, but they also have high PTH. So just to remind, in most cases of chronic renal failure, the reason why they have high calcium, it's the total calcium that's high, and for some reason they, in these cases, they will have an increased complex part, which is the one that's complex to the phosphate, citrate or lactate. So if you measure ionised calcium, if you see on this diagram, they're still the same.

So primary hyperparathyroidism. It is uncommon. And as I say, most of the time there, it's an adenoma affecting a single parathyroid gland.

The ionised calcium is high and the PTH is usually high or high normal. And in most of these cases, you, you can't palpate a mass and ultrasound in some cases can be helpful, but in some, it doesn't actually, identify mass either. In some cases, you can actually have both glands affected, and then in, in those cases, they may be easier to, to detect, but that just depends on the, the actual, case individually.

The keyshound appear to be genetically, predisposed to this disease, and there are reports of these cases, these animals developing primary hyper hyperparathyroidism, and then receiving treatment that's worked, and then it's reoccurred several years down the line with another. Case of primary hypothyrothyroidism. So vitamin D, this is mainly an overdose of some compound or some, some plant or anything that has a source of vitamin, vitamin D that, that's excessive intake.

And it can be due to, as I say, overdose with, calcitriol, which is, one of the treatments when we use with hypoparathyroidism. So we're now talking about the reverse, so a low calcium. And also if you ingest certain plants, which cats tend to like things like that.

And also the psoriasis creams, the anti psoriasis creams often contain vitamin D, and cats and dogs seem to love them in some cases and therefore can result in toxicity. The warfarin antagonists or vitamin K antagonist type poisons, if you look at these, most of these in the recent years have been had a lot of vitamin D added to them, and they use this as part of the way of causing the lethal effect to the, you know, the animals are trying to kill. So you need to be careful with that because we, we can also get significant vitamin D toxicity and hypercalcemia from that, as well as trying to, cause a coagulation problem.

So just a bit more about the vitamin D, but the vitamin D toxicosis can actually be very severe and it is related to the amount that is consumed by the actual individual. And the more that they consume and the more rapid the effect and the increase in calcium, the clinical signs are therefore more severe. And you often see high phosphorus in these cases, and they can, if they're not detected early enough, can result in tissue mineralization and therefore, the prognosis becomes poorer.

So these cases are the, the PTH independent, they have a low PTH and they they usually have, in, in most cases, it depends on the source, a high 25 hydroxy vitamin D or the, the calcidol. They, in some of these cases, particularly the plant and sometimes the psoriasis creams, the 25 OHD or the calciol will be normal and therefore, you need to measure the calcitriol, which is the 125 dihydroxy, vitamin D, if that's normal. Sorry, if the other one's normal, the 25 hydroxy vitamin D.

Just brief mention, granulomatous disease. This is always one of the differentials that's thrown in, and it does occur. The, the mechanism appears to be to do with cytokines and macrophages and increasing the synthesis of calcitriol or vitamin D3.

And any granulomas disease could be classed as Animals with injection site reactions or a widespread paniculitis or something like that. The blastomycosis I mentioned, I mean, these are obviously going to be more common in, in other countries rather than the UK. It's not really a common, presentation that we get systemic fungal disease.

Obviously, in these cases, the underlying disease process may actually present as, that's the, the actual presenting clinical signs rather than the, the high calcium, which may be found incidentally. So in cats, just, I just mentioned them briefly because in cats, the courses are all similar in cats and the, the same things apply. Again, neoplasia, probably the most common, and then chronic renal failure again can be related to, but obviously, as I keep saying, it's mainly total calcium in these cases unless they have that coexisting tertiary hyperparathyroidism.

And then in cats, What's, what seems to be most common, and, and they do report it as the most common in the states, but it's probably getting quite common in this country, is idiopathic. Now, this is really a diagnosis of rule out where you, you've excluded all the other causes, and we can't find the reason why this cat has high calcium and therefore, it Just has to be managed. Now.

Luckily, most of these cases actually show no clinical signs, or the ionised calcium itself is only minimally elevated. So they tend to do quite well if it can be controlled. I don't know why it's caused.

They, they say there's some sort of increased sensitivity to vitamin D in some of these cases, or there's some dysfunction in the, the calcium receptors. It's not, it's not really known, exactly what causes it. So just a brief thing on signalment, just remember.

Addison's in the dog does tend to affect younger animals. Now, obviously, it can be at any age that's affected, but it, the mean, sorry, the median age is about 4 years. And there's various breed predilections, predilection, sorry, and genetic basis.

So just need to remember when, when this might be a possible underlying cause, if you've got a hypercalcemia that's picked up. Primary hyperparathyroidism. Though, and it is less common, is an older dog, disease.

And as I said, there is a genetic basis in the keyso and other, breed predilections, as well. And some of them are listed there. And as I've mentioned before, idiopathic in the cat, wide range, no sort of pre-liction to any particular breed or any age, and apart from possibly long hairs, maybe overrepresentative.

And again, primary hyperparathyroidism is quite rare in the cats. I think some of these might get overlapped with older cats that have chronic renal disease and they have the tertiary hyperparathyroidism. So, it, again, like the dog, primary hyperparathyism, hyper, sorry, hyperparathyroidism, is not that common.

So going on to clinical signs, I've listed some clinical signs here. We talk about dogs first, but in a lot of these cases, these animals have come in for another reason. And when you've done the screening on the blood, you've picked up a high total calcium or it's only marginally That, you know, increased and therefore they're presenting signs aren't always these signs that you see here like a PUPD case.

So coming thinking back to it, quite a lot of presentation of older or not so older animals, but animals coming into the vet is yes, it's PUPD. So remember, it's always a differential for that presenting sign. It can also be very vague clinical signs, they're off colour, or food, etc.

And if they've got a particular cause, not just obviously primary hyperthyroidism, but other causes, it may be that disease process that's more obvious than, you know, the, the actual results of the high calcium. And remember that obviously Addison's normally has, can have a very variable presentation and it can be difficult to diagnose. But primary hyperparathyroidism may only present with, say, a dog that's got repeated or a cat, sorry, with repeated UTI infections, or you've got urus, so calcium oxalate, urulists.

So without any other clinical signs. In the cat, they often show very little, and as they do with most diseases. They're often anorexic is the most common clinical sign, and then you can get the, the various vague signs that cats show, which is not eating, vomiting, etc.

And which can be, you know, the clinical signs of lots of different diseases. So it's quite vague and not particularly specific. The, as I said, the idiopathic hypercalcemia, which is becoming quite common.

May have no clinical signs and it's, it's only identified incidentally. Again, they can get stones secondary to, to high calcium. And in the, in the cat, vitamin Dtoxicy similar to the dog, quite vague signs, depends on the, how much they've ingested again with rat poisoning.

And again, primary hyperparathyroidism, clinical signs can be mild or non-existent. And in these cases. So clinical signs depend on how high the ionised calcium is and how fast it increases.

So I've given you levels there at the bottom. You usually don't see any clinical signs until the ionised calcium is greater than about 1.75 and 1.8, and I can say that most of the cases and a lot of the animals or, you know, patients that we have that are measuring calcium.

They, a lot of them are not that level when we, when we first diagnosed them. I mean, some, some different, I'll go on to them later, but some specific cases, particularly neoplasia, can often result in quite high levels, and those are more like the levels and also vitamin D toxicity, like the levels that you see where they should be critically ill, which is greater than 2, 2.2 for the ionised calcium, which is very high.

So the diagnosis of hypercalcemia is made when you can make it on total calcium, but that's unreliable because great then if you took those total calcium, a lot of those, if you don't went on to measure ionised calcium, that the ionised calcium would be normal. So we need to look at the ionised calcium. And in dogs, once you're above the reference range, same in cats, once you're above the reference range, that is hypercalcemia.

That's how tight this reference range is. So anything above those levels is considered a hypercalcemia. And if you get those on a repeated basis, then you should, you know, take them seriously.

So diagnosis of hypercalcemia, preferably ionised calcium. Obviously, if you have a total calcium that's really high, like 4 milli per litre, and it's on a, you know, persistent basis, then your ionised calcium will probably be high as well. And then once you've measured your ionised calcium and you've confirmed that it's high, you need to go on a measure of parathyroid hormone.

And preferably, this needs to be done with a repeated ionised calcium measured on the same sample. If you go back to what I was talking about, the control path, you know, The actual physiological control, the PTH is involved in minute to minute control. So if we take a sample on one day and then take an ionised calcium a week later, they aren't necessarily going to correlate.

So we need to do it on the same sample. The, the PTHRP obviously, you can measure that with suspected cases of malignancy, and they do tend, quite a lot of cases of anal sac adenocarcinoma. And some of the lymphomas will have an elevated PTHRP, but you must remember that if your PTHRP comes back low, it doesn't exclude malignancy, particularly if your, PTH is also low.

So remember that it's not, you know, a, a normal PTHRP doesn't exclude, a neoplastic cause. And we can also obviously measure the two different types of vitamin. D.

So we've got hydroxy vitamin D, and we've got 125 hydroxy vitamin D, which is, calcitriol. We normally do the first one. You can measure the first one, the, the 25 hydroxy vitamin D first, and if it's normal, then go on and look at calcitriol, you know, depending on the, the actual suspicion of what's causing the vitamin D, toxicity.

So to remind you, ionised calcium, serum sample, not gel, separated. No, EDTA or anticoagulant type, plasma samples, they're, they're not. They will result in completely, you know, spurious results.

The sample needs to be collected, sorry, anaerobically and you exclude air and then you separate it and then put it into a separate tube again, excluding air. Anything like chemolysis or the exposure of cells and so, you know, phosphorus from cell, etc. They will affect the, the ionised calcium.

So, and it often what it does is it actually lowers the, the actual, ionised calcium. And if you're trying to confirm a high calcium, and you've got a hemolazed sample or some, or a sample that's been exposed to actual cells, and you, you get a result that's sort of like in the reference range near the top, but not above it, then you don't know. So you need a separated sample, and send that.

The PTH and the PTHRP have a completely different sample collection. There are special kits that we can send out to you on request from the specialist laboratory where it's measured. And these are plasma samples collected into EDTA which are, and the, the tubes are, are cooled prior to sampling.

Then the sample is separated. And then once it's separated, it should be frozen immediately and kept frozen until the sample is sent by a courier on ice packs to the lab for analysis. If you do not collect the sample like this, or the sample defrosts and goes up to room temperature instead.

Like that for any particular length of time, then what it results in is a degradation of the PTH and the PTHRP. The A protein is supposed to help decrease the, degradation speed of this. And the PTHRP is particularly sensitive to this and you'll end up with low levels.

So the sample must arrive at the lab frozen. So a chart that we actually have in our book that we send out with the, the, well the specialist came, lab, sorry, they have this in the, in part of the, the manual there. And it's just showing a comparison of ionised calcium.

So, the labels gone over there, but the PTH is at the left-hand side and the ionised calcium obviously is labelled on the bottom, just showing normal and, you know, the, the two different causes. Now, Primary hyperparathyroidism obviously is up in this right-hand corner because you've got high PTH and high ionised calcium. And the other two here, they've separated them, so they've got secondary hyperthyroidism and PTH independent hypercalcemia.

Those really are in, in similar groups. It just depends on the, the cause there. Because the secondary.

In most of these, in these cases, if you, if you go back to what I'm saying, they present as a high, they can have a, a high total calcium and a normal ionised calcium or they have high ionised calcium. So they've split these, split these up. But, as I say, there's two different, groups, primary and secondary.

The vitamin D measurement, which the specialist lab deals with, actually, there, there aren't any current places as far as I know. And if anybody knows, please correct me. But we send them over to the states and it's serum sample and it should, if you're going to submit it to the lab, it should be sent, you should freeze it prior and and just send it chilled, and we normally send it over on ice packs.

It doesn't have to be, kept at minus whatever, but it just needs to be kept chilled, and that's, that's a serum sample. So this was just the approach to diagnosis of hypercalcemia to use. I mean, it's quite useful if you're, just for a quick look, if you have a case.

So you start with the total calcium and then you confirm that with ionised calcium and then you go on to measure the other, you know, PTH, etc. Depending on what you find. And, and that's quite useful as an, an overview to help.

So treatment I'm just gonna go through just a few, slides with this, but it's, it's really, I have no experience on this, and this is all what's gathered from the references and what's normally, used. You need to consider, first of all, when you have a hypercalcemic case and you initially diagnosed that, does it actually need treatment now or can we go on and diagnose it and find out what's causing it? It does depend on the level of calcium that's present.

And also the rate of development. So, if the levels aren't that high, you're not going to need any of this immediate treatment like trying to, correct the levels to avoid, adverse effects on, you know, your, your neuro neurological system, cardiac, renal dysfunction, etc. And those are, as I say, they're usually when you've got high levels of calcium.

So we're looking at total calcium greater than 4, ionised calcium greater than 2.2. OK.

So if we have these cases that, that That, sorry, if we, we have a case of hypercalcemia. When we, when we go to treatment, initially, we need to try and diagnose what's causing it, because obviously, the treatment of the and removal of the cause will result in resolution. So it, it does depend on the cause and depending on the levels of high calcium, whether we need to do some initial supportive therapy, like fluid therapy or diuretics, etc.

To try and decrease the levels of calcium. The steroids that I mentioned there are more a long-term treatment in hypercalcemia, and they really shouldn't be used in initial, treated, you know, treatment of cases. One, because if you think about it, cases of Addison's, you start treating with steroids, you're gonna have, if you haven't actually diagnosed it at that at that stage, it's on this, you know, it's a, it's an acute crisis case that's presented.

The fluid therapy itself will help resolve the clinical signs and therefore, you can go and do your test prior to actually starting any steroids and therefore interfering with the test for Addison's. So the, the steroids should be left until later, I think, in most of these cases. And also, if you have neoplastic causes, particularly lymphoma.

They can interfere with trying to diagnose that, particularly if you're going to do, cytology, say if they've got enlarged lymph nodes as well, that will interfere if you've used steroids prior to that to make a diagnosis, and it will also interfere with the histology. And also chemotherapy at a later date. There some people do advocate using, steroids prior to doing chemotherapy.

It can actually decrease the efficacy of certain chemotherapy, Protocols. OK. So we try and use that as a, as a later on in the disease, particularly if we've not actually, either reached the diagnosis or it's a, it's a cause of hypercalcemia that cannot be resolved easily.

Calcitonin can also be used in the treatment. It's usually used in combination with other therapies. It's quite expensive and it's, in some dogs in particular, they can have severe side effects secondary to it.

The bisphosphonates, are quite common. They are usually, they're used if the steroids aren't working or you're gonna get, you know, the animal or particular patient has side effects secondary to the steroids. So they can, they can use, be used quite, readily and there's lots of different types.

They, and that, as I say, often when you don't know the actual underlying cause or you, you can't resolve it. And also specific treatment for Addison's obviously will, should resolve your hypercalcemia. And then I just mentioned aotemic chronic kidney disease.

I mean, there's other texts for that, but this, as I mentioned prior, sorry, previously, the low dose calcitriol therapy can be helpful in these cases to, to improve quality of life, but you have to be careful and monitor the actual doses to, to avoid resulting in, high, levels of calcium and therefore getting the secondary hypercalcemia. And then a specific treatment for vitamin vitamin dose D obviously stop them ingesting it is the main one. And then it, depending on how level, how high the levels are, you may need aggressive therapy to try and reduce the ionised calcium initially.

And then you can use, calcium phosphate, non, sorry, calcium-containing phosphate binders to try and, you know, just to reduce the, the level of calcium. In the case of primary hyperparathyroidism, the main treatment of choice seems to be surgery. It does obviously depend on the, the, the, the clinicians or the, the institution, etc.

As to what they might use. But surgery tends to be the, the main treatment of choice and seems to be fairly, well, I should say easy, but it's, it is reasonably, straightforward. If you, if you're fairly experienced.

There is an issue that you may have, a hypocalcemia that results secondary or immediately after surgery, but bear, bear in mind this is not that common. You have to remember the other thyroid gland, if this is a unilateral case, will be very tiny and probably won't be active. So in some cases, you may have to supplement, for, or, you know, to try and avoid the low calcium.

So pre-treatment with calcitriol. Vitamin D can be helpful in some of these cases. There are other ways of, of, removing the, enlarged gland and you've got ethanol ablation, which sounds a bit old school, but, and also ultrasound guided radio frequency heat ablation has been used.

So, prognosis, the Depends really on the underlying cause. So cases of primary hyperparathyroidism have usually quite a good prognosis, particularly if you can remove the gland, except in the keysho, you've got to bear it or keyshound, you've got to bear in mind that you've got to warn the owner that some of these cases that actually can reoccur. So they, they may develop it several years down the line.

And Addison's obviously has a, has a good prognosis if it's well-controlled and hyperfitamosis D if you, you know, you get rid of the actual cause and you can, you know, determine what's actually resulted in the overdose. Cats with idiopathic hypercalcemia, it's quite tends to be quite a low level of hypercalcemia, and they often do well with just, treatment, medical treatment. And primary hy parathyroidism again, quite rare, but it's quite, the prognosis is quite good in cat.

I've just put this little table to the, to the side. Obviously, The neoplastic causes and various, if they have chronic renal disease and they've got this tertiary hyperparathyroidism, the prognosis can be fair to guarded depending on to what's going on and, you know, where the tumour is and whether it's responding to chemotherapy, etc. Etc.

So, You know, it just depends on the cause, but quite a lot of the causes, if you can identify them, have a reasonable prognosis. So just to summarise, the clinical signs are often mild, and I'd say quite a lot of the cases present as incidental and the fact that you've picked it up because they've been presented for another reason or other clinical signs. And the ionised calcium in these cases is important to try and confirm that we have a hypercalcemia.

Once you've confirmed that the, the ionised calcium is high, we then need to measure a PTH plus a minus a PTHRP and the PTH should be measured with a repeat ionised calcium done on the same sample. Sample collection, remember the serum only, no air, ionised calcium, and remember the, the PTH has a special collection, protocol and kit, which needs to be followed to avoid falsely low levels of either of these two PTH either the PTH or the PTHRP. And then treatment ideally is to remove the underlying cause and identify it.

Now, I know we've had a lot of cases and I've talked to other vets and our clients when they've been trying to determine what's causing the high calcium. It's not always as easy said, you know, we've ruled out primary hyperparathyroidism and then we were trying, going for a fishing trip to try and find out what's causing the, the, the calcium. And I would say that neoplasia tends to be the most common, but in some cases, you, you don't find anything.

And then I think you just really need to, to monitor and try and control the, the levels. A lot of these animals can be older animals and therefore, you must remember they may have other underlying disease processes which could be affecting the, the calcium and particularly older cats, which have multiple things like chronic renal disease. So in, in all, the prognosis is fairly good if we can determine the, the underlying cause and try to, to manage it.

So, That's the end. So if you've got any questions, hopefully not lots, then, then feel free. Anthony are you there?

You go away. It does say he's on muted, but Anthony, if you could, can you hear me OK? Yeah.

Sorry, and Katerina in Russia. So people listening in from all over the world, I saw Indonesia before as well. So it's been great to have so many people obviously also from the UK, but, people listening in from all over the world, and I think there are some questions, so, I will move over to those in a second, but do put your questions in the, in the question box, and obviously just use the chat for any technical things or telling us where you're listening in from.

We have a question from Amaral who says, what is the minimum recommended fasting period to measure calcium? I think in most, in most cases, it's the, the normal overnight fast, but we, it doesn't seem to affect it to a great degree if it's maybe had a tiny feed. So I, I would, we would tend to say with most samples that we have that you need to do an overnight fast.

We're talking sort of like 10, you know, 10 hours, 1012 hours, I would say. It's not always an issue. It's not gonna, it's not gonna affect the, the sample quality and therefore, the actual levels in that respect, but preferably faster, yeah.

That's great, Stacey. We've also got, Victoria saying, did you mention about measuring ionised calcium and PTH on the same sample? I thought the preparation of the samples are different.

They are different. You're exactly right. What I, what, what I was trying to say is that you need to collect enough sample, therefore, you have a serum sample for your ionised calcium, and you also have a sample that goes into the EDTA.

OK, and they need to be taken at the same, preferably the same time or within, you know, fairly close length of time, because I mentioned the PTH has a minute to minute control on the ionised calcium. So, yes, yeah. Yeah, otherwise you're, the, the results you get won't be synchronised, will they?

No, no. That's great. Hillary's asking and saying slightly off topic, but is it possible to have a hyperphosphattemia and normal calcium level and no other obvious clinical signs other than bone decalcification.

I have had a cat with a systemic CNS fungal infection with hyper, high hypophosphemia and normal calcium. Yeah, I'm sure, I'm sure you can. What she's saying the ionised calcium is not, not high.

Yeah, saying normal calcium level, which I presume is ionised. Yeah, I mean, pho phosphorus and calcium are, are linked as well, and they do affect the, each other's levels. So it depends on what, if, it depends on what, if they have some local pathology involving the, the bone.

I mean, phosphorus tends to be in In most of it, in, in primary, well, I've got a, I did have a diagram of this, but, it, it does tend to be low in most of the cases where you're getting hypercalcemia rather than high. And if you do get a high phosphorus apart from the vitamin D toxicity, if you do get a high phosphorus in some of these cases, it can, it often related to, renal disease at the same time. So I'm not sure how it links unless she's got some local bone pathology or, or, or some dietary thing that's affecting it.

You know, if it's something like that. Yeah, I think she was saying a fungal infection maybe of the bones, so maybe that's been on the bone. Well, that's, that's probably what, that's probably what they might cause it.

Sorry, I, I, I, I didn't hear you say fungal, but then I, you've said it now. But yeah, if they have some local effect on the bone itself, it's, it can result in changes in, in calcium and phosphorus levels and it just depends on how it's, the pathology of it, yeah. Yeah, it was systemic CNS fungal infection, she said.

And she then goes on to say, have used nationwide for PTS PTH testing, excellent advice and service for this, so there you go a little. OK. Feather in your cap, good place to to be sending off PTHs.

Michelle has asked the question, and I must admit she's stolen my question because I was going to answer it, ask it as well. How does one take an anaerobic sample? Can you describe this, please?

Right, I've had this question asked by several people actually. And basically, when we say anaerobic sample, it's preferably, you've taken the sample, I obviously, you've taken the sample, needle, syringe, and then you've put the sample, preferably, you know, obviously through, through the, the cap of the other, the other two, you know what I mean? I it up.

Then, yeah, rather. Up and then you've got that sample, obviously, and we now need to separate it. And the way, the way to do that's not so easy, but as long as you have minimal air contact, that's fine.

Because we have a, there's an equation we use at the lab to it's the pH change is what the, if you have prolonged contact to air, it, it causes a pH change and lowers ionised calcium. So we have a, an actual correction factor for that. But if you have minimal You know, contact with her during that transition, that's how you do it.

I mean, it's obviously not going to be absolute unless you have like a chamber that you can do it in, which most people don't. We've got, Gertie asking the question, why does hypercalcemia cause a PUPD? Why does it cause a PUPD?

Yeah. I, I think it's for relation to the actual effect on the kidneys and the vitamin D and therefore, with, with hypercalcemia, affecting the renal tubular function, you, cause with, if you have high calcium, the, the way it's supposed, it affects the tubules. And, it can actually damage them as well.

It just depends on how long they've been having the the high calcium for because if you have high calcium for a while, you will actually result in toxicity to the, the renal tubules and therefore, they will, you will get lost in tubular function and therefore you can actually get renal disease secondary. And that, that's, that's one of the main mechanisms, but these are obviously more chronic cases. If it was short term, I'm not necessarily, wouldn't necessarily say that you would see PUPD that might be another cause.

But the high calcium by itself on prolonged, you know, prolonged levels of it will result in, destruction of renal tubules. That's great. Thank you so much for that.

We've got Pushproop asking . What sort of percentage of pets have hypercalcemia? Is this a common or a rare condition that you're seeing in the lab?

Right, I don't, I don't think I've got actual percentage, but I do, from just going back over the cases I think we've had in the last year or so, there, it's not that common. I would say more often we get occasional false, you know, we're going to get possibly false flows, but actual high calcium in, in the last year, I would say I've probably only seen, and these are ones that probably that we've confirmed with ionised calcium. I don't know, maybe about 100.

Out of the whole year, do you see what I mean? And we see hundreds a day of places. So it's not so high.

No, it's not. And I think this is, this is one of the things though. I mean, it sounds like it is common, but I think it's mainly because it's total calcium that we're getting that might be high.

And then when you actually go on to check it, it's not, it's, it's the ionised calcium is normal and it's the total calcium that's high. Great, yeah, and the ionised is the key one and this isn't it, yeah. We've had somebody here say this is more a question with regards to the presentation, but I know that IEX labs have the top reference range for total calcium in dogs is 2.7, whereas on the slide, the high range is 3.

Is this due to different lab settings and measurements, or should we be looking at 2.8 and 2.9, of total calcium being normal?

OK. Right, the reference ranges for the total calcium I took as a coagulator, or a combination of other lots of sources, including our own. I'm not so worried about that.

It can vary between labs. It's the ionised calcium, it tends to be tight, tight, and the ranges are fairly similar across various sources. So the total calcium, no, it can be variable.

Yeah. Yeah, so I think with all things, this is where I know when I first qualified, I kind of thought the pathologists were gods, Stacey, and then I realised that none of us have all the answers and we have to interpret bloods and it goes in then with clinical signs and with everything else as well with the history, doesn't it, that we don't just say. It's a high level.

Therefore, we believe it because I thought it was beautiful for you as a pathologist to say sometimes some results can be spurious because it's, it's just the way it is, isn't it? Yes, yes. And if it doesn't, the key thing that everybody always talks about is if the, if the results don't fit with the case that you have, then don't believe them.

That's, that's all I can say. And it's, I think it's then where the actual relationship between vet and pathologists is really important that you can, you know, get yourself on the phone and, and kind of say, well, this is also what I was worried about and, and then there's that lovely sort of interchange of ideas which can help both sides, can't it? Yes, definitely.

Yeah, if you're worried about anything or something doesn't make sense and the results are not what you're expecting, you need to ring and speak to somebody. And we're always happy to, to speak to you. If, if for some reason you can't get somebody right away, leave them, you know, we will always ring you back, we'll always ring you back.

So, yeah, sure. And I think sometimes, you know, I always say with a webinar, if, if I can take one thing away from a webinar, then that hour has been worthwhile and, you know, I'm sure that, you know, still you will get samples for calcium that will come through a gel tube and then of course it makes life terribly difficult, doesn't it? So it's, it's making sure we take samples in the, the correct fashion that gives you a much better chance of, helping us make the diagnosis, doesn't it?

Yes. Stacey, I think we, there are a few other questions that I would suggest to people because I, I'm conscious that it is getting later. Mhm.

Please do feel free to email info at Northwest Labs for specific for specific questions, but thank you so much for coming on. It is such a. An interesting area because it's not so black and white, we have to think outside the box to, to help us make diagnoses as well.

Obviously, thanks to Nationwide Labs for making this, you know, a free talk so people can view it. Many hundreds of vets and nurses on during the lunchtime, which is fabulous, you know, that you're making that commitment to yourselves. And those of you are listening, I would just encourage you to go onto our site because of course, virtual conference is coming up in 2 weeks and there are some free parts of the conference as well as parts that you'll have to pay for.

So do go and have a nose if you haven't already. And hopefully we'll see you on a webinar very soon, but again, Stacey, thanks for a great webinar and thanks to Nationwide for making it possible. OK, thank you.

Thank you, take care, bye bye. OK, thank you. Bye.