Thyroid metabolism in the recessive sex-linked dwarf female chicken. 2. Binding of thyroid hormones by serum proteins.

Serum protein profiles were studied together with serum binding sites and capacity for L-thyroxine in dwarf and non-dwarf White Leghorn and White Rock breeds at ages 1 wk., 4 wks. and in laying hens. Serum protein profiles varied with breed, strain and age. The percent gamma-globulin fraction was greater (P less than .05) in dwarf 1 wk. old and laying hens of the White Leghorn breed when compared with the normals. The only difference found in the White Rock breed was a decreased level of albumin in dwarf laying hens. There were no significant differences in the capacity or sites of binding of L-thyroxine to serum proteins although greater amounts of L-thyroxine were bound to globulin fractions in the dwarf. The data were interpreted to suggest that changes in serum protein profiles may have been the result of hypothyroidism at the cellular level but there was no reason to suspect abnormal binding of thyroid hormones to be the cause of that hypothyroidism.