Effects of different gonadotropin pulse frequencies on corpus luteum function during the menstrual cycle of rhesus monkeys

In the nonfertile menstrual cycle, the frequency of episodic LH secretion declines from approximately 1 pulse/h in the early luteal phase to 1 pulse/4-8 h in the mid- to late luteal phase, but the relevance of this phenomenon to the initiation of functional luteal regression is not completely understood. We investigated whether a reduction in LH pulse frequency causes a decline in luteal progesterone production by experimentally reducing LH pulse frequency during the early luteal phase, and measured the effects on the subsequent plasma progesterone pattern and the onset of luteal regression. These results demonstrated that a GnRH, hence LH, pulse frequency of 1 pulse/8 h is able to maintain luteal function and thus indicate that a reduction in LH pulse frequency such as that which occurs during the spontaneous menstrual cycle is not sufficient to promote luteal regression.