The relationship of androgen to the thyrotropin and prolactin responses to thyrotropin-releasing hormone in hypogonadal and normal men.

Fluoxymesterone, an androgen not converted to estrogen, caused a significant decrease in the TSH response to TRH in 11 men with primary hypogonadism [maximum change in TSH: before treatment, 11.3 +/- microU/ml (mean +/- SE); 8.9 +/- 1.0 after 2 weeks (P less than 0.001); 8.2 +/- 1.1 after 6 weeks (P less than 0.01)]. There was a significant fall in serum T4-binding globulin (TBG) (measured directly by RIA) without a change in the free T4 or free T3 index. Fluoxymesterone had no effect on the PRL response to TRH in hypogonadal men. The results suggest that 1) androgen per se is at least partly responsible for the lower TSH response to TRH in men compared to women and 2) androgen is not a cause of the lower PRL response to TRH in men.