Testosterone metabolic clearance rate and production rate in the male infant rhesus monkey

The male infant rhesus monkey (Macaca mulatta) undergoes a period of testicular activation similar to that seen in the human infant. Plasma testosterone (T) concentrations rise after birth, reaching levels of about 500 ng/dl at 1-3 mo of age and then fall to approximately 50 ng/dl at 6 mo. The plasma T metabolic clearance rates (MCR(T)) and production rates (PR(T)) were measured in two rhesus infants at 1 and 6 mo of age to determine the mechanism of the observed increase in plasma T. While there was little change in the MCR(T) between 1 and 6 mo, PR(T) was much higher at 1 mo than at 6 mo of age. These observations are consistent with the hypothesis that the increased plasma testosterone levels in infant rhesus monkeys reflect an increased production of testosterone rather than an altered metabolic disposition of the hormone.