Patterns of sex hormone receptor expression in stimulated endometrium from oocyte donors.

In patients with high serum E2 embryo transfer is often postponed, as high E2 levels adversely affect embryo transfer outcome. We aimed to determine if stratified serum oestradiol (E2) and progesterone (P4) levels differentially affect endometrial histology and endometrial oestrogen and progesterone receptor protein levels. Endometrial biopsies were collected from oocyte donors. Samples were divided based on peak serum E2 levels into three groups: (i) low-E2 (n = 33) E2≤2999pg/mL; (ii) mid-E2 (n = 40) E2 3000-4999 pg/mL; and (iii) high-E2 (n = 15) E2≥5000 pg/mL. Oestrogen receptor alpha (ERα) and progesterone receptors A and B (PR) protein levels in endometrial stroma (S), glandular (GE) and luminal (LE) epithelia were assessed by immunohistochemistry. Samples in high-E2 group demonstrated strongest association with accelerated endometrial maturation (2 (1-2); 2 (1-3); and 3 (2.8-3) median days of advancement of endometrial maturation respectively in low, mid, high-E2 groups, p = 0.046). There were significant differences in ERα and PR immunoexpression in S, GE and LE among the groups (p < 0.05). Higher E2 levels were associated with decreased ERα expression (p < 0.017) in GE and LE, and increased PR expression in S and GE (p < 0.011 and p < 0.0001, respectively). Higher serum E2 levels were associated with impaired endometrial steroid hormone receptor expression, higher serum P4 and more advancement of endometrial maturation.