Age Related Changes in Serum Levels of Gonadotropins and Testosterone in Infantile Male Rhesus Monkeys1

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Abstract
The developmental patterns of gonadotropin and testosterone levels in serum were studied in 6 male monkeys bled at frequent intervals for the first several months after birth. Serum luteinizing hormone (LH) levels were measured using an in vitro bioassay (the rat interstitial cell-testosterone assay; RICT) and, in some instances, a radioimmunoassay. Follicle stimulating hormone (FSH) and testosterone were measured by immunoassay alone. Serum concentrations of testosterone, FSH and biologically active LH were elevated during the first 3-4 months of life in all 6 animals studied. Thereafter, circulating concentrations of these hormones declined to relatively low or undetectable levels. Thus, the results of this study demonstrate that the hypophyseal-testicular axis of the male monkey is quite active during the early neonatal period.