Categories: Cat Health

Feline Hypothyroidism

by Michael
(London, UK)

Feline hypothyroidism is thyroid deficiency. It is rare in cats. It most commonly occurs after operations on the thyroid gland or treatment for hyperthyroidism. It is a dysfunction of the thyroid gland, which is in the cat’s neck.

An inadequate amount of thyroid is produced by the gland. The prefix “hypo” in medical terms means “low, under, beneath, down, below normal”1. The suffix, “-ism” means, “condition of, practice of, theory of”2.The deficiency of the thyroid hormone “impairs new hair growth and prolongs the resting phase”5. The resting phase of hair growth is called the “telogen” phase3. Hair growth is not continuous.

This causes a gradual thinning of the coat and makes it look dull.

In addition the cat might be lethargic, be constipated, gain weight, have brittle hair, be constipated, have excessive thirst4 and be mentally dull.

Another sign that the cat might exhibit is a type of dwarfism in which the head is enlarged with a short neck and legs.

Feline hypothyroidism is diagnosed through a blood test.

Treatment consists of daily hormone replacement therapy. This has to be carefully gauged as too much can result in hyperthyroidism4.



3. The Cat, Its behavior, Nutrition & Health


5. Cat Owner’s Home Veterinary Handbook page 111.

From Feline Hypothyroidism to Cat Health Problems

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Feline Hypothyroidism

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Dec 08, 2010 Hi Gail
by: Michael

Gail, I don’t get notifications of comments so I am sorry for responding so slowly.

I don’t know what typical cat readings are. But you are correct in saying that meds for hyperthyroidism should slow the production of thyroid (thyroxin).

Sorry I can’t be of more help. Good luck.

Feline Hyperthyroidism

Aug 30, 2010 Hyper vs Hypo
by: Gail (Boston, MA USA)

Hi Michael, I’m just a tad confused and would appreciate a bit of information to sort things out.

Sadie was diagnosed with hypErthyroidism and takes the medicated chewy treats. On her last visit, the vet told me to halve her meds because her thyroid reading came in at 46. What’s confusing me is that I thought the meds were to slow down her thyroid not speed it up, so why would a reading come back so low? Do you know what a cat’s normal range would be?

In humans, a normal thyroid reading is somewhere between 90 – 130 (or, in my case 150 according to my doctor and I have hypOthyroidism). Are you able to shed some light? Thanks very much.

Aug 27, 2010 Another good one thanks
by: Ruth

Thank you Michael for another invaluable article. I hope everyone saves all your pages for future reference.

Michael Broad

Hi, I'm a 71-year-old retired solicitor (attorney in the US). Before qualifying I worked in many jobs including professional photography. I have a girlfriend, Michelle. I love nature, cats and all animals. I am concerned about their welfare.

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