Adipocyte insulin action during the normal menstrual cycle

The relationship between the menstrual cycle and insulin sensitivityis unclear. The aim of this study was to investigate insulinsensitivity during the normal menstrual cycle using the physiologicalinsulin target organ adipose tissue. A total of 23 normal healthyvolunteers were studied, nine of whom were in the follicularphase, and 14 of whom were age and body mass index-matched andin the luteal phase of the menstrual cycle. Adipocyte insulinreceptor binding was measured and adipocyte insulin action wasassessed by measuring initial rates of 3–0-methylglucoseuptake and by inhibition of lipolysis. The maximum specificinsulin receptor binding was significantly higher in subjectsstudied during the follicular phase of the menstrual cycle comparedto subjects studied during the luteal phase (1.81 ± 0.13versus 136 ± 0.15% per 10 cm2 cell surface, P < 0.05).Maximum rates of 3–0-methylglucose transport were 1.70± 0.22 versus 1.75 ± 0.22 pmol/10 cm2/5 s in thefollicular and luteal phase respectively and were not significantlydifferent between the two groups. The maximum percentage lipolysisinhibition observed was 42.5 ± 7.5% in the follicularphase and 39.9 ± 7.4% in the luteal phase (not significant).This study demonstrated that there is a reduction in insulinreceptor binding in the luteal phase of the normal ovulatorymenstrual cycle. The post-receptor action of insulin is notaffected between the two phases of the menstrual cycle.