Metabolic clearance rate and blood production rate of testosterone and dihydrotestosterone in normal subjects, during pregnancy, and in hyperthyroidism

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Abstract

The metabolic clearance rate (MCR) and blood production rate (BP) of testosterone (T) and dihydrotestosterone (DHT), the conversion of plasma testosterone to plasma dihydrotestosterone, and the renal clearance of androstenedione, testosterone, and dihydrotestosterone have been studied in man. In eight normal men, the MCRT (516±108 [SD] liters/m2/day) was significantly greater than the MCRDHT (391±71 [SD] liters/m2/day). In seven females, the MCRT (304±53 [SD] liters/m2/day) was also greater than the MCRDHT (209±45 [SD] liters/m2/day) and both values were less than their respective values in men (P < 0.001). In men the conversion of testosterone into dihydrotestosterone at 2.8±0.3% (SD) was greater than that found in females, 1.56±0.5% (SD) (P < 0.001). In five pregnant females the MCRT (192±36 [SD] liters/m2/day), the MCRDHT (89±30 [SD] liters/m2/day) and the conversion of testosterone into dihydrotestosterone (0.72±0.15%) (SD) were significantly less than the values found in nonpregnant women. In five females with hyperthyroidism, the MCR for testosterone and dihydrotestosterone were similar to those observed in pregnant females, but the conversion of testosterone into dihydrotestosterone (2.78±1.7%) (SD) was greater, and similar to that found in men. In men the production of dihydrotestosterone was 0.39±0.1 (SD) mg/day, 50% being derived from the transformation of plasma testosterone. In women the production of DHT was 0.05±0.028 (SD) mg/day, only 10% coming from testosterone. During pregnancy, the production of testosterone and dihydrotestosterone are similar to that in normal women. In three patients with testicular feminization syndrome (an adult with hyperthyroidism and two children) these two MCRs were greatly reduced compared to the normal females, but the conversion of testosterone into dihydrotestosterone was in the limits of normal male range

Authors

J. M. Saez, M. G. Forest, A. M. Morera, J. Bertrand