Kinetics of3H-5α-Dihydrotestosterone Metabolism in Normal Men and Women and Men with Prostatic Carcinoma: Effects of Estrogen Administration in Men12

Abstract

Following a single injection of ³H-5α-dihydrotestosterone, we studied the plasma kinetics of 5α-dihydrotestosterone metabolism in normal men and women and in men with prostatic carcinoma prior to and during estrogen therapy. The mean metabolic clearance rate for four normal young women (274 L/24 hr) was significantly less than that (745 L/24 hr) for eight normal young men. The inner volume (V₁) and outer volume (V₂) were significantly lower in women than in men. The metabolic rate constants (K₁ and K₂) were not significantly different between the two sexes. Four older men with prostatic carcinoma studied prior to gonadectomy or any medical therapy had parameters in the ranges for normal young women. The administration of oral estrogen to these older men decreased the values for the metabolic clearance rate and the volumes of distribution to even lower values. Similar changes were found when oral estrogen was given to two normal young men. Estrogen caused a decrease in the rate of metabolism (K₂); this contrasts with our earlier studies with testosterone where we found that estrogen caused K₂ to increase.