Follicular Development during the Luteal Phase of the Human Menstrual Cycle

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Abstract
The aims of the present studies were to determine the number, size range, health, and steroidogenic activities of antral follicles in normal human ovaries during the luteal phase of the menstrual cycle. Steroidogenic activity was assessed from the levels of androstenedione, testosterone, and estradiol in follicular fluid and the levels of extant and FSH-stimulable aromatase activity and FSH-stimulable progestin synthesis in the granulosa cells. Data for luteal phase ovaries were compared to those obtained for ovaries from the late follicular phase. On average, 94% (range, 70–100%) of the luteal phase follicles (≥1 mm diameter) were atretic as assessed by oocyte viability and granulosa cell number. The largest healthy follicles during the mid- to late luteal phase were 4–4.5 mm in diameter; these contained high levels of aromatizable androgen (500–2000 ng/ml), low levels of estradiol (P < 0.05). These data suggest that the number of healthy luteal phase follicles (≥l mm diameter) available for subsequent preovulatory development is limited. (J Clin Endocrinol Metab56: 1022, 1983)