For a study, researchers sought to determine the efficacy of circulating vascular endothelial growth factor (VEGF) and its receptor, soluble FMS-like tyrosine kinase-1 (sFLT-1), as peripheral indicators of endometrial remodeling in normally ovulating women during the menstrual cycle in connection to reproductive hormones. A prospective cohort study at a U.S. university research facility, included 96 healthy, regular menstrual ovulatory women aged 18–44. Up to eight times in a single cycle, vascular endothelial growth factor and sFLT-1 were evaluated in concurrently collected plasma, serum, and urine. Serum was tested for reproductive hormones. Mean VEGF and sFLT-1 concentrations were examined during the cycle, and relationships across specimen types were computed. Harmonic models were used to calculate the relationships between VEGF and sFLT-1 and hormonal pattern features.

There was no difference in VEGF or sFLT-1 levels over the menstrual cycle. VEGF concentrations in plasma were 31.2 pg/mL (24.1, 56.9), serum was 194.1 pg/mL (125.4, 350.2), and urine was 101.7 pg/mL (64.2, 165.8) during the menstrual cycle. Urine and plasma measurements were not consistently associated, although plasma and serum measurements were. Although sFLT-1 was related to a larger mean and amplitude of estradiol, vascular endothelial growth factor was not consistently associated with reproductive hormone concentrations.

Circulating VEGF and sFLT-1 levels did not alter during the menstrual cycle, indicating that they are unlikely to be helpful peripheral biomarkers of endometrial abnormalities. Plasma might be the ideal medium for research detecting circulating VEGF for other reasons, and scheduling to the menstrual cycle phase did not need to be addressed for reproductive-age women.