Endometrial glandular proliferation and estrogen receptor content during the normal menstrual cycle

Hysterectomy specimens from 35 normally cycling premenopausal women were examined to determine the relationship of endometrial glandular proliferation to estrogen receptor content. The cases were divided into follicular phase (n = 20), early luteal phase, days 1-5 post ovulation (n = 5) and mid to late luteal phase (n = 10). Proliferation rates, as determined by MIB-1 expression, were maximal in the endometrial functionalis during the follicular phase (701 cells/1000), decreased by half during the early luteal phase (327 cells/1000), and virtually ceased during the mid to late luteal phase (8 cells/1000) (p < 0.001). Estrogen receptor status, determined immunohistochemically and graded on a scale of 0 to 4+, averaged 3.4+, 2.2+ and 0.5+ during the follicular, early luteal, and mid to late luteal phases, respectively, in the endometrial functionalis (p < 0.001). Proliferation rates in the endometrial basalis paralleled those in the functionalis, but at a lower rate, whereas estrogen receptor expression underwent considerably less cyclical variation. We conclude that estrogen receptor status shows a highly significant correlation with glandular proliferation rates and are predictive of endometrial proliferative changes during the normal menstrual cycle.