SUN-537 Progesterone Therapy and Serum Sclerostin Levels in Healthy Menopausal Women: A 3-month Randomized, Placebo Controlled Clinical Trial

Sclerostin is an osteocyte-produced glycoprotein that inhibits the WNT/β-catenin pathway essential for bone formation. Sclerostin was postulated to relate to normal bone metabolism in 2001; we still have an incomplete understanding of its regulation. Estradiol, a bone antiresorptive ovarian steroid, inhibits sclerostin. Estrogen and progesterone act together in menstrual cycles and bone remodelling with progesterone exerting an anabolic effect. We hypothesized a relationship between progesterone and sclerostin because progesterone and estrogen are “partner” hormones in most tissues, and because progesterone and sclerostin modulate bone formation in opposite directions. Two observational menstrual cycle studies have reported sclerostin levels; neither documented changes across cycles nor in luteal phases during which progesterone levels are high(1)(,2). Some reports have also shown positive correlations between sclerostin and age and BMI. In this study, sclerostin was measured using an assay (MSD) of high sensitivity (LOD ± 1pg/mL), broad detection range (1-10 000 pg/mL), and intra/inter-assay precisions of 6% and 10% respectively(3). We collected fasting serum during a 3-month double blind randomized controlled trial (RCT) of 300 mg oral micronized progesterone vs placebo in symptomatic menopausal women; progesterone significantly decreased hot flushes/night sweats (vasomotor symptoms, VMS)(4). Statistical analysis showed sclerostin was not related to the 28-day baseline VMS Score (r=.18, p=.22). Pearson correlation coefficients were used to evaluate sclerostin vs baseline data and ANCOVA to analyze RCT results (alpha=0.05 significant, [SD]). The study’s purpose was to determine if sclerostin levels changed during a 3-month RCT of progesterone for VMS in healthy menopausal women(3). The primary outcome was sclerostin level in the 3(rd) month adjusted for baseline and randomization. Results showed the 52 participating women had a mean age of 55.2 (4.6) years, height 1.60 (0.07) m, weight 66.4 (8.6) kg, BMI 24.9 (2.9) kg/m(2) and were primarily Caucasian (91.2%). Baseline variables did not correlate with the baseline mean serum sclerostin level of 27.9 (10.2) pmol/L. Sclerostin had no statistically significant relationship with progesterone or placebo therapy during this RCT; mean changes were -1.07 and -2.60 pmol/L respectively. These data are the first evidence that progesterone neither increases nor decreases serum sclerostin levels. These data fit with the lack of menstrual cycle changes in sclerostin levels(1)(,2). That sclerostin did not correlate with age and BMI in this RCT is likely due to their low trial variance. A limitation of this study is the small sample size. However, it has considerable strength in its RCT design that can document causation. (1)Cidem M Gyn Obstetric Invest. 2012; (2)Liakou CG Endocrine 2016; (3)Van Lierop AH J Bone Miner Res 2011; (4)Hitchcock CL Menopause 2012.