Parathyroid cancer, tumors and Hyperparathyroidism in Dogs


Hyperparathyroidism in Dachshund

Question: Dr. Richards, My 10 year old miniature dachshund Sweetpea recently had a blood test that came back with an elevated calcium level of 12.7. She was to have cryosurgery at Ohio State Univ. vet hospital for a benign melanoma on the sclera of her left eye and that is why we had the blood tests. She had laser surgery on this eye two years ago because at that time the melanoma was on the iris.

My vet has sent another blood sample to Michigan State's Vet lab for further testing. She suspects a tumor on the parathyroid gland since Sweetpea did not have any of the other things she suspected such as anal gland tumors.

My questions are are these parathyroid tumors usually malignant? Could this be related to the melanoma that she has had for 3 years? What exactly are the additional blood tests going to tell us? Also, she has been on Prednisone many times during her life because of ongoing problems with intervertebral disk disease. She finished a three week course of Pred in mid-December. Could this medication be a factor in the test results? Thank you so much for your help.

Answer: N-

It is a good idea to recheck calcium tests at least once, and sometimes two or three times, prior to believing that the calcium is actually elevated. It can help, when possible, to get an ionized calcium test, which can help to clarify the importance of the rise in total calcium serum levels. We have found a single high calcium level in serum tests on a number of dogs who did not have elevated calcium levels on subsequent lab work.

Assuming that the calcium rise is real, there are several possible problems. Malignant cancers (lymphoma, anal sac adenocarcinomas, others), kidney failure, hyperparathyroidism, hypoadrenocorticism (Addison's disease), diseases that destroy bone and a currently unavailable form of rat poison are the causes that I can think of. I think that the order these are listed in is approximately most common to least common.

When hyperparathyroidism is present, the lab work usually shows high calcium levels, low phosphorous levels and increased levels of parathyroid hormone (PTH) and there should be no evidence of kidney disease in the lab work.

If this is hyperparathyroidism, the most likely cause is a benign tumor of the parathyroid gland, followed by malignant tumors of the gland and then hyperplasia (increase in gland size not from cancer). As far as I know, the only treatment for these conditions is surgical removal of the parathyroid gland tumor or hyperplastic region.

Hope that this helps some. Mike Richards, DVM 1/15/2001

Parathyroid gland tumor - in Blue Heeler

Question: Dear Dr. Mike, I Have a 14 1/2 year old female spayed Queensland Blue Heeler named Windy. Two years ago during a routine exam and lab work her calcium level was noted to be slightly elevated, 11.5. My vet told me that an elevated calcium level can be indicative of a cancer somewhere in the body. They did an abdominal ultrasound and found a mass. She underwent exploratory surgery and they found a large benign necrotizing lipoma which they removed. Everything else looked normal as far as they could tell. A repeat calcium level post op was 10.3. All of her other labs have been normal except for a slight elevation of her ALT which has been stable in the 200 to 400 range for about 2 years. Her next blood work about 6 months later again showed an elevation in calcium to 11.9. My vet suggested we could do all kinds of diagnostic work ups to try to find the cause. Because of my dogs age and the fact that she has been acting perfectly normal ( eating, active, peeing and pooping fine) I decided to be conservative and just follow it. For the next 1 1/2 years her calcium remained between 11 and 12. Windy has remained completely asymptomatic. Even my vet has been stumped. She says that if she had cancer somewhere it would surely have shown up by now. Last month she had repeat lab work and now her calcium is up to 13.2. I took her to UC Davis where she had an ultrasound of her thyroid and abdomen. Her abdomen is fine, however she has multiple nodules on one side of her parathyroid gland. The other side apparently looks normal. The recommendation is surgery. I guess this is not a very common thing in dogs. I have called around to several vets and most of them have only done a few cases. I have her scheduled or surgery in 2 weeks. Can you tell me a little about possible post op complications. i am most worried about what if the other side dosen't wake up and kick in. I have been assured that this should not happen, but I am trying to get as much info as possible. Thank you Ursula


Answer: It is a good idea to have this sort of surgery done at a veterinary school. The biggest complication to removing a functional parathyroid gland tumor is exactly the one you are worried about. Even when there is only one tumor, affecting one gland, it usually has caused enough suppression of the ability to regulate calcium to make for a scary period post-surgically. It helps a lot to have lots of students to monitor patients on a regular basis for a day or so to be sure that hypocalcemia won't occur. It is usually only necessary to supplement calcium for a few days but it is a really important few days since low calcium levels can be fatal. I haven't had to deal with this problem in a dog but we do have seen this in cats due to surgery for hyperthyroidism damaging the parathyroid glands. I don't' actually do that surgery, either -- but we have managed a couple of patients through the complications.

As long as everyone is aware of the possibility of complications and takes precautions, this usually works out fine. The long term complication rate from parathyroid surgery is supposed to be very low.

Mike Richards, DVM 9/14/2000

Parathyroid adenoma

Question: My question is about my 9 year old male Portuegese Water Dog who has had a really bad year and still is not doing too well. From 1/99 through 2/99 he was treated with some major antibiotics for what my vet thought was an infection of a disc space. In late Feb. 99 he had surgery to remove bladder stones. He still didn't recover very well (continued to drop weight, no energy) Finally, we noticed his blood calcium level increasing and further tests revealed a parathyroid problem. My vet sent him to a surgeon who removed a parathyroid adenoma in 4/99. To make a long story a little shorter, he still hasn't recovered and he now has a major fear/hatred of vets and vets' offices. Since 4/99, he has been to the vets maybe 10 times, mostly for blood tests. These tests have shown no really significant problems (calcium was well within the normal range). He continues to drop weight and is now about 48 lb. down from a normal of 62 lb. He eats very little and rejects all but his favorite food (which is canned Pedigree chicken--not my idea of a great diet) He appears to have great gastic distress and vomits frequently. My vet now has him on Reglan and Pred (5 mg/day) When he does eat, his gut is very noisy and he is restless, pacing back and forth. Pepto Bismol does sometimes give relief. I suspect the antibiotics and surgeries and various tests and meds have really messed up his system but the question is where we go from here. My vet usually refers to Ohio State Vet School and I've taken a few dogs there over the years and been very pleased with the results. The problem is that I'm not sure this dog could stand the work up. He now quivers and quakes if I even put him in the car and throws up instantly when we arrive at the vets (I should mention that this dog was a show dog for the first 4 years of his life and travel and new people never bothered him before). Do you have any suggestions for testing that might be done locally? Any theories about this problem? Thanks and I apologize for the length of this request.


Answer: m-

I have looked through the references that I have on parathyroid disorders. One reference, "Clinical Endocrinology of Companion Animals" by Chastain and Ganjam contained information on a condition known as multiple endocrine neoplasia. In this syndrome, parathyroid tumors are associated with tumors of the adrenal glands, pituitary glands, pancreas or thyroid gland. This condition had been reported in one dog at the time of publication of their book. I am not sure if there have been subsequent cases reported, or not. While this many not be the most likely problem since it seems to be fairly rare, it might explain the incomplete recovery and it seems reasonable to look for signs of problems in these other organs, such as digestive enzyme deficiencies, hypoglycemia (low blood sugar), increased drinking and urination, hair loss or palpable masses. Your vets may have already considered this possibility but it might be worth asking about. I think that your local vets can help you determine if there appears to be a chance that this is the problem. Ultrasound exam is probably the best way to look for adrenal gland tumors and pancreatic tumors but that is probably only necessary if there are at least some clinical signs that one of these problems is present.

There are lots of other medications to consider for the GI distress. Cimetidine (Tagamet tm), famotidine (Pepcid AC tm) and ranitidine (Zantac tm) all are sometimes helpful in gastrointestinal problems as they are all protective of the gastrointestinal lining. Cisapride (Propulsid Rx), which helps move ingested food through the digestive tract is sometimes helpful when metoclopramide (Reglan Rx) doesn't work well enough. W. These medications all do have specific purposes and randomly using them isn't the best way to figure out which one is necessary but sometimes it is the only practical approach. Of course, switching medications isn't necessary if the current ones are working well enough.

I do think from your description of weight loss and continued GI distress that something more is wrong. While I don't have extensive experience with parathyroid adenomas my impression is that there aren't usually long term side effects except sometimes persistent low blood calcium, which hasn't been your experience.

I don't have much advice on how to get your dog to accept going to the vet's again. Sometimes if we dispense a pain relief medication and a mild sedative (like butorphenol and acepromazine or hydrocodone and diazepam) and have the owners administer them an hour or so before the office visit it helps to relieve tension enough that a dog can readjust to coming into the office. This doesn't always work and it can even make the situation worse by lowering inhibitions about biting, so we are careful when we try this approach.

Your vet was pretty astute to pick up the hypercalcemia and recognize its significance, so it seems likely that he or she will be pretty good at recognizing the signs of the other potential endocrine cancers. Hopefully there won't be any, though.

Mike Richards, DVM 1/5/2000


Michael Richards, D.V.M. co-owns a small animal general veterinary practice in rural tidewater Virginia. Dr. Richards graduated from Iowa State University's College of Veterinary Medicine in 1979, and has been in private practice ever since. Dr. Richards has been the director of the PetCare Forum...