Variations in ovarian steroid levels during the luteal phase of the menstrual cycle.

1. Six subjects were investigated during the luteal phase of the menstrual cycle to determine whether the ovarian steroids, estrogen and progesterone were released in an episodic manner. 2. Analysis of plasma obtained every 20 min. during a normal working day provided no evidence for pulsatile release of either steroid although values were lower in the afternoon than in the morning (p less than 0.001). A good correlation (r=0.908) was obtained for the release of both hormones. 3. Cortisol secretion was inversely related to that of the ovarian steroids.