Circulating Vascular Endothelial Growth Factor and Soluble fms-Like Tyrosine Kinase-1 as Biomarkers for Endometrial Remodeling Across the Menstrual Cycle.

OBJECTIVE To characterize variation in circulating vascular endothelial growth factor (VEGF) and its receptor, soluble fms-like tyrosine kinase-1 (sFLT-1), across the menstrual cycle in normal ovulating women in relation to reproductive hormones to identify the utility of VEGF and sFLT-1 as peripheral biomarkers of endometrial remodeling. METHODS Ninety-six healthy, regularly menstruating ovulatory women, aged 18-44 years, enrolled in the BioCycle Study, a prospective cohort study at a U.S. academic research center. Vascular endothelial growth factor and sFLT-1 were measured in concurrently collected plasma, serum, and urine up to eight times across a single cycle. Reproductive hormones were measured in serum. Mean concentrations of VEGF and sFLT-1 were compared across phases of the cycle, and correlations between specimen types were calculated. Harmonic models estimated associations between VEGF and sFLT-1 and characteristics of hormonal patterns. RESULTS No variation in VEGF or sFLT-1 levels were detected over the menstrual cycle. Median (25th percentile, 75th percentile) concentrations of VEGF during the menstrual cycle were 31.2 pg/mL (24.1, 56.9) in plasma, 194.1 pg/mL (125.4, 350.2) in serum, and 101.7 pg/mL (64.2, 165.8) in urine. Plasma and serum measures were consistently correlated, whereas urinary measures were not. Vascular endothelial growth factor was not consistently associated with reproductive hormone concentrations, although sFLT-1 was associated with higher mean and amplitude of estradiol. CONCLUSION Circulating VEGF and sFLT-1 did not vary across the menstrual cycle and therefore are unlikely to be useful peripheral biomarkers of endometrial changes across the menstrual cycle. For studies measuring circulating VEGF for other reasons, plasma may be the preferred medium and timing to menstrual cycle phase need not be considered for reproductive-age women.