Peripheral serum progesterone and correlated endometrial glycogen levels during the menstrual cycle of Macaca arctoides

Peripheral serum progesterone levels and endometrial glycogen content in the M. arctoides have been determined during the normal menstrual cycle. Progesterone values rose on Day 11, were maximally elevated on Day 23, and then declined with the onset of menstruation. Correspondingly, the endometrial glycogen concentration was minimal during the follicular phase and showed a marked postovulatory rise followed by a significant decline during the late secretory phase of the menstrual cycle. These findings compare favorably with similar events observed in the human and suggest that the M. arctoides is a monkey species whose reproductive physiology may allow for comparative interpretation with the human female.