Serum from cats with hyperthyroidism does not activate feline
thyrotropin receptors
(March 2002)
The background for the study. Hyperthyroidism
is far more common in cats than in other animals. The usual causes
are a toxic uninodular or multinodular goiter, but a few cats seem
to have a diffuse goiter, raising the possibility that they have
the feline counterpart of Graves' disease. This study determined
the structure of the receptor for thyrotropin (TSH) in feline thyroid
tissue and studied whether the receptor can be stimulated by serum
from cats with hyperthyroidism or humans with hyperthyroidism caused
by Graves' disease.
How the study was done. The structure
of the TSH receptor in feline thyroid tissue was determined by molecular
methods. Feline and human receptors were inserted into kidney cells,
and the binding of TSH and serum from cats with hyperthyroidism
and humans with hyperthyroidism caused by Graves' disease was measured.
The results of the study. The feline
TSH receptor was found to contain 763 amino acids, 1 amino acid
less than the human, bovine, canine, murine, ovine, and rat TSH
receptors. It most closely resembles the canine receptor and is
90 percent identical to the human TSH receptor. The functional characteristics
of the feline and human TSH receptors were similar. Serum from 16
cats with hyperthyroidism did not stimulate feline TSH receptors,
whereas serum from patients with Graves' hyperthyroidism did.
The conclusions of the study. The
structure of the feline TSH receptor is similar to that of the human
TSH receptor. Serum from humans with Graves' hyperthyroidism, but
not serum from cats with hyperthyroidism, activates feline TSH receptors,
indicating that there is no feline counterpart to Graves' hyperthyroidism
in humans.
The original article. Nguyen LQ,
Arseven OK, Gerber H, Stein BS, Jameson JL, Kopp P. Cloning of the
cat TSH receptor and evidence against an autoimmunity etiology of
feline hyperthyroidism. Endocrinology 2002;143:395-402.
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