Endometrial development during the transition to menopause: preliminary associations with follicular dynamics.

This study aimed to test the hypothesis that the development of functional luteal phase dominant follicles (LPDFs) is associated with increased endometrial growth as women transition to menopause. Endometrial thickness (ET), follicle development, and hormone production were characterized in ovulatory women of mid-reproductive age (MRA; 18-35 years,  = 10) and advanced reproductive age (ARA; 45-55 years,  = 16). Transvaginal ultrasonography was conducted every 1-3 days during one interovulatory interval to quantify ET and the diameters of follicles ≥2 mm. Blood was drawn at each visit to measure progesterone, estradiol, inhibin A, follicle stimulating hormone, and luteinizing hormone. In the MRA group, ET was lower (8.87 vs. 10.1 mm) in women with typical versus no LPDFs, in association with greater luteal phase estradiol (91.1 vs. 48.8 ng/l). In the ARA group, luteal phase endometrial growth was greater (12.0 vs. 10.4 mm) in women with typical versus no LPDFs, in association with lower progesterone (10.7 vs. 13.8 μg/l; LPDF effect  < 0.1) and inhibin A (35.6 vs. 51.17 ng/l;  < 0.10). Preliminary findings suggest that ET may be increased in women who develop LPDFs, in association with reduced luteal phase progesterone and inhibin A, during the transition to menopause. Continued research is required to confirm these findings.