Someone on another post raised the question of dogs and cats being hypothyroid. I became curious and found this article in the Merck Manual on treating animals with hypothyroidism:
merckvetmanual.com/endocrin...
I was struck by this:
Tests that may confirm the diagnosis include measurement of the serum concentrations of total T4, free T4, and TSH; provocative thyroid function tests (eg, TSH stimulation test); thyroid gland imaging; and response to thyroid hormone supplementation. Choice and interpretation of diagnostic tests is based heavily on the index of suspicion for hypothyroidism.
and this:
Total T4 concentration is the most commonly performed static thyroid hormone measurement and is a good initial screening test for hypothyroidism, with a diagnostic sensitivity of ~90%.
and this:
Unfortunately, serum TSH concentrations remain within the reference range in 20%–40% of dogs with confirmed hypothyroidism.
Interesting. Vets don't rely solely on the TSH test as doctors treating humans are advised to do.
Also: In practice guidelines for diagnosing humans with hypothyroidism I see little emphasis on cholesterol levels . Not so for animals:
The classic hematologic finding associated with hypothyroidism, found in 40%–50% of cases, is a normocytic, normochromic, nonregenerative anemia. The classic serum biochemical abnormality is hypercholesterolemia, which occurs in ~80% of dogs with hypothyroidism. The value of serum cholesterol determination as a screening test for hypothyroidism cannot be overemphasized, because cholesterol concentrations are a sensitive and inexpensive biochemical marker for this disease in dogs. Other clinicopathologic abnormalities may include high serum concentrations of triglycerides, alkaline phosphatase, and CK.
Perhaps endocrinologist (and GPs, too) should be required to study the diagnosis and treatment of animals with hypothyroidism.
Unfortunately, in this particular document, I see no mention of also providing endogenous T3 to hypothyroid animals who do not improve on T4 therapy.