Daily levels of sex hormones in 15 subfertile women formulate a menstrual cycle profile predominant with progesterone secretion

Introduction: Changes in sex hormone secretions during the menstrual cycle may affect fertility. It has been shown that a prematurely raised progesterone (P4) level after therapeutic injection of human chorionic gonadotropin caused changes in endometrial gene expres-sion and lowered the pregnancy rate. The aim of the present study was to investigate the complete menstrual patterns of P4 together with its derivatives testosterone (T) and oestradiol (E2) in subfertile women during their natural cycles.Material and methods: Daily serum levels of P4 (ng/mL), T (ng/mL), E2 (pg/mL), and sex hormone binding protein (SHBG, nmol/L) were measured throughout a single 23-28-day menstrual cycle in 15 subfertile women aged 28-40 years with patent oviducts and nor-mospermic partners. Knowing SHBG levels, the free androgen (FAI) and free oestrogen (FEI) indexes were calculated for each cycle day in each patient.Results: Baseline (cycle day one) levels of luteinising hormone (LH), thyroid stimulating hormone (TSH), P4, and T were comparable with reference intervals for a normal cycle, whereas follicle stimulating hormone (FSH), E2, and SHBG exceeded those. During cycles, the levels of P4 correlated positively with E2 levels (r = 0.38, p < 0.05, n = 392) and negatively with T (r = -0.13, p < 0.05, n = 391). T correlated negatively with E2 (r = -0.19, p < 0.05, n = 391). Menstrual cycle phases were hidden. The curve of the mean/median daily levels of P4 rose prematurely, was parallel with the E2 rise, and culminated closely, but with more than 4 times greater amplitude of P4 (2571% of baseline levels in day 16) than of E2 (580% in day 14). In turn, the curve of T declined in a U-shaped manner with a nadir (-27%) on day 16. Averaged daily levels of FEI, but not FAI, varied significantly between 23 and 26 days long and the 27-28-day cycles.Conclusions: 1. Throughout the entire menstrual cycle length in subfertile women, P4 secretion predominates quantitatively over secretions of the re-maining sex hormones when menstrual cycle phases are hidden. 2. The rise of E2 secretion is in parallel with the P4 rise, but with 4 times lower amplitude of E2. 3. T secretion declines and is inversely related to both P4 and E2 secretions. 4. Changes in E2 bioavailability are related to menstrual cycle length. (Endokrynol Pol 2023; 74 (1): 106-112)