Effects of Methyl Testosterone on Thyroid Function, Thyroxine Metabolism, and Thyroxine-Binding Protein

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Abstract
A study of the influence of methyl testosterone on human thyroid function is presented. The drug induced a striking fall in thyroxine-binding capacity of the thyroxine-binding alpha globulin of serum in all patients, and a less striking but consistent increase in the fractional rate of thyroxine disappearance from blood. Other findings were a slight fall in the serum protein bound iodine, an increase in circulating free thyroxine, and an increase in the amount of thyroxine degraded per day. There were inconstant effects on the thyroidal and renal clearance of iodide. The hypothesis is offered that a fall in concentration of thyroxine-binding protein in serum is responsible for the changes observed. A consistent rise in serum cholesterol was also noted during the administration of methyl testosterone.