Effect of Hyperthyroidism and Hypothyroidism on the Metabolism of Testosterone and Androstenedione in Man

ABSTRACT The plasma concentration, metabolic clearance (MCRT) and plasma production rates of testosterone, the metabolic clearance rates of androstenedione (MCRA), the conversion ratios and rate transfer constants of these steroids were studied in hyperthyroidism and hypothyroidism. In hyperthyroidism there occurred a significant decrease in both the MCRT and conversion ratio of testosterone to androstenedione. These changes were associated with an increased plasma level of testosterone in both sexes resulting in a normal plasma production rate of the androgen. The MCRA and MCRA/m2 in hyperthyroidism was not significantly different from normal. However, the conversion ratio of androstenedione to testosterone was significantly increased in this disorder. The rate transfer constants of testosterone and androstenedione were unchanged from normal. Following return to the euthyroid state the values returned to normal. Hypothyroidism was associated with an increased MCRT, MCRT/m2 and conversion ratio of testost...