[The effect of testosterone on the secretion of prolactin]

For 21 days, nine male monkeys received daily doses, 8 mg of testosterone propionate dissolved in almond oil. After an initial period of 6 days, a control period was observed during which only the almond oil was administered. Each injection was preceded by the taking of a 10 ml blood sample. The prolactin and steroids (testosterone and oestradiol) were measured by radioimmunoassay. For both groups of animals the prolactin serum count increase significantly after 10 days of treatment. This modest increase (approximately 50% a base count) is more systematic among the immature subject than among the mature ones. The oestradiol serum count increased among the same animals on day + 2 and remained at a noticeably high level from day + 2 to day + 20. These results suggest a stimulatory effect of testosterone on the secretion of prolactin due to the conversion of androgen to oestradiol. However a mild testosterone action directly on lactotropic cells is not to be discounted.