Relationship between menstrual cycle and glucose metabolism in healthy young Japanese women

Abstract

Background: The menstrual cycle, which is regulated by estrogen and progesterone, may influence glucose metabolism. Previous findings have remained inconsistent, and few studies have focused on Japanese women.Methods: We investigated seven healthy young Japanese women with regular menstrual cycles (25–38 d). Each participant underwent a 75-g oral glucose tolerance test (OGTT) during both the follicular and luteal phases as determined by self-reported cycles. Fasting and post-load glucose and insulin levels were measured at 0, 30, 60, and 120 min. Estrogen, progesterone and HbA1c levels were also measured. Glucose tolerance was classified according to the Japan Diabetes Society criteria, and indices of insulin resistance (HOMA-IR), β-cell function (HOMA-β), and the insulinogenic index were evaluated.Results: Estrogen and progesterone levels were significantly higher during the luteal phase than those during the follicular phase. Thirty minutes after glucose loading, plasma glucose values were high during the luteal phase (P=0.02), whereas insulin showed a tendency towards increasing values at 30 and 120 min (P=0.06). Although no significant differences were found in fasting indices of HOMA-IR or HOMA-β, the insulinogenic index was significantly lower during the luteal phase (P=0.03) compared to that during follicular phase.Conclusions: The luteal phase is associated with impaired postprandial glucose handling and reduced early insulin secretion. Therefore, menstrual cycle phase should be considered when evaluating glucose metabolism in young premenopausal Japanese women.