Evaluation of an immunoradiometric assay for thyrotropin in serum and plasma samples of dogs with primary hypothyroidism.

A commercially available immunoradiometric assay was used to measure the thyrotropin (TSH; thyroid-stimulating hormone) concentration in the serum and plasma of 23 dogs. The basal concentration in five dogs with histologically confirmed primary hypothyroidism (median 0.18 microg/l, range 0.16-0.72 microg/l) was slightly, but not significantly, higher than that in 13 clinically healthy dogs (median 0.09 microg/l, range 0.06-0.34 microg/l). The TSH values in 11 euthyroid dogs with various dermatological diseases (median 0.09 microg/l, range 0.05-0.53 microg/l) were significantly lower than in the hypothyroid dogs, but there was considerable overlap. The assay alone was therefore not capable of giving a firm diagnosis.