Excessive Drinking, Vomiting Water, Normal Bloodwork

My 15 year old cat, Taz was diagnosed with hyperthyroidism 2 months ago. His coat is greasy, matted and looks terrible. He is constantly shedding. He had dropped to 12 lbs despite 3 meals a day (normally 15 lbs). Bloodwork was normal except for slightly altered liver values and T4 was elevated indicating hyperthyroidism. The vet wasn't concerned about the liver values. He said they were close to the normal range.

We started him on felimazole 2.5 mg twice daily for the last 2 months. In this time he has experienced increased thirst and urination. He has been vomiting puddles of water usually in the early morning. I spoke to the vet again. He suspected kidney disease or diabetes. We just repeated bloodwork again. All values were normal. It's not diabetes. Kidney function BUN and creatinine levels were normal. The SDMA test was 16 which is one point above normal. Thyroid was too low so we will be reducing his thyroid medication.

His coat still looks matted and yucky. His weight is better but he seems lethargic.

Thoughts?

Forgot to add, urine was dilute and specific gravity was low.

Hi. I am so sorry your guy, Taz, is going through this. I am curious as to what the vet thinks about the dilute urine since that is generally as sign of some sort of kidney issue. Did they say?

Most of the issues he is having are possible side effects of the felimazole. Does the vet say that the meds might have anything to do with it? Perhaps, the lower dosage will help with that?

The matting could also be related to the meds, primarily because of the lethargy. However, it can have joint pain as a side effect as well. If Taz has any arthritis at all, it would only exacerbate that and can cause a lack of grooming.

Wish I could be of more help, but those are my thoughts and I hope they illicit some questions/ideas for you.

I would have your cat get a complete urinalysis.

Dilute urine and low specific gravity points to kidney disease. I know...I have a cat with kidney disease.

The complete urinalysis is a more definitive indicator of kidney disease than just bloodwork alone.

I know they did a urinalysis with the first bloodwork. Not sure if it was a complete urinalysis or a limited one. I will have to ask. I plan on calling and getting a copy of his bloodwork results.

I suspect this is early onset kidney disease. This is what I got from the SDMA website:

SDMA is a more reliable and sensitive indicator of kidney function in animals. SDMA increases earlier than creatinine in dogs and cats with both AKI and CKD and unlike creatinine, SDMA is not impacted by lean muscle mass. SDMA increases on average with 40% loss of kidney function versus creatinine, which does not increase until up to 75% of kidney function is lost. Creatinine is a breakdown product of muscle and is therefore impacted by lean body mass, whereas SDMA is not.

Urine specific gravity (USG)—Loss of urine concentrating ability progresses with kidney disease and dysfunction, and it is apparent before metabolic wastes such as BUN and creatinine increase. This change occurs with approximately 67% loss of nephron function but is variable.10 SDMA may increase in patients with early kidney disease that can still concentrate their urine. Natural fluctuations in USG are common in healthy animals and are influenced by how much the animal drinks prior to urine collection. Poor urine concentration is not specific to the kidney and can be influenced by other diseases (e.g., diabetes, liver disease, and Cushing’s disease) versus SDMA, which is influenced by changes in GFR. Finding a persistently increased IDEXX SDMA concentration and inappropriately concentrated urine suggests kidney disease is probable and immediate action should be taken.

This is interesting:
https://www.idexx.com/files/idexx-sdma-test-algorithm.pdf

Lowering the dosage of the Felimazole should help improve his kidney function. Treating hyperthyroidism is generally detrimental to kidney function, but untreated hyperthyroidism can cause heart problems (and is also damaging to the kidneys) so it is more important to treat the thyroid problem first, then deal with possible kidney disease second.