Formation of pinopodes in human endometrium is associated with the concentrations of progesterone and progesterone receptors.

Objective: To investigate the relation between the development of endometrial pinopodes and the serum concentration of hormones and the distribution of estrogen receptor-alpha, estrogen receptor-beta, progesterone receptor A, and progesterone receptor B.

Design: Prospective clinical study.

Setting: Hospital-based unit of reproductive health and university-affiliated reproductive research laboratories.

Patient(s): Twenty-seven healthy fertile women with normal menstrual cycles.

Intervention(s): Urine and blood sampling for hormone measurement, vaginal ultrasonography, and endometrial biopsy.

Main Outcome Measure(s): Appearance of the endometrium on light microscopy, pinopode formation, serum levels of luteinizing hormone (LH) and follicle stimulating hormone (FSH), and expression of progesterone receptors A and B and estrogen receptors alpha and beta.

Result(s): Pinopode formation and regression were closely associated with increases and decreases, respectively, in serum progesterone concentration. At pinopode development, levels progesterone receptors A and B in the glandular and luminal epithelial cells decreased; this effect was mainly dependent on the absence of progesterone receptor B. Serum estrogen levels and levels of estrogen receptor alpha and beta did not correlate with pinopode formation.

Conclusion(s): The increase in serum progesterone level and down-regulation of progesterone receptor B are important in development of pinopodes.