Inhibitory Effect of Testosterone on Luteinizing Hormone Secretion in Immature and Adult Rats

Abstract

Immature and adult male rats were castrated and injected for 14–23 days with either sesame oil or testosterone propionate in varying doses. Plasma LH was elevated at the termination of the experiment in both immature and adult control rats. Testosterone propionate prevented the elevation in plasma LH and lowered hypophysial LH in doses which appeared to be slightly larger than those required to return the weight of the accessory sex organs to that found in intact controls. Three to 4 times less testosterone (per unit body weight) was required to repress the rise of plasma LH in immature than in adult rats. This suggests that a change in the hypothalamic sensitivity to the negative feedback of testosterone may be responsible, at least in part, for the onset of puberty in the male (Endocrinology76: 412, 1965)