Distribution of total estradiol receptor levels in various segments and tissues of the normal and pathological human uterus

Estradiol receptor (RE₂) levels were measured in normal (n = 22) and pathological (n = 14) human endometria and in various segments and tissues of the same uteri (n = 8). The highest total estradiol levels (TRE₂) were found in midcycle normal cyclic endometria and the lowest in the secretory phase of normal cyclic endometria and in normal postmeno-pausal endometria (the TRE₂ levels in the latter two groups were within similar ranges). The highest nuclear RE₂ levels were found in proliferative-phase normal cyclic endometria. TRE₂ levels in pathological postmenopausal endometria were high, in the range of those found in proliferative normal cyclic endometria, but the nuclear RE₂ levels were low as compared with those in normal proliferative endometria. Examination of the distribution of the TRE₂ levels in various segments and tissues of normal proliferative uteri revealed similar trends in all cases as follows: The highest levels were measured in the functional endometrium (fundus) and the lowest in the myometrium (fundus). Basal endometrial TRE₂ levels decreased along the longitudinal axis from fundus to isthmus. In 4 cases, TRE₂ levels in leiomyoma tissues were higher than those in the corresponding myometrium. These results indicate the possibility of a differing regulating mechanism of the RE₂ in various segments or tissues of the human uterus.