[Mechanisms in the homeostatic regulation of the gonadotropin-secreting system. Circadian rhythm of gonadotropin LH].

: After describing and discussing the mechanisms that control the secretion of gonadotropins and the action of their releasing factors, the study describes a series of tests in which luteinizing hormone (LH) levels were measured in both male and female healthy subjects at intervals of 4 hours and of 15 minutes, to detect possible rhythmic variations. Tests were also conducted to study the response of LH to its specific releasing factor (LRF), by measuring LH levels at different times after iv injection of LRF. The test results ruled out and daily rhythm, but revealed periodic "pulsations" in the release of LH with peaks at intervals of approximately the same duration both by day and by night. The effect of LRF appeared to be slightly higher in the morning, while in the afternoon and night it produced 2 peaks at intervals of approximately 60 minutes, possibly as a result of its double function of mobilizing LH and stimulating the synthesis of new LH.