Abstract

The purpose of this study was to investigate the effect of menstrual cycle phase on the insulin/glucose relationship at rest and response to sub-maximal exercise. Eight eumenorrheic women completed exercise sessions (60 min, 70 VO2max) in the follicular (day 7 +/- 2) and luteal (day 20 +/- 2) phases of their cycles. At 45 min before each exercise session the subject consumed an oral glucose load (OGL) of 1 g/kg body weight in a 400 ml solution. Blood samples were obtained before the OGL (-45 min) immediately before exercise, and at 15 min intervals until the end of exercise (60 min). Results indicated that serum glucose and insulin increased due to the OGL and decreased due to exercise. No significant phase differences were observed for the glucose responses: however, insulin levels were greater immediately before exercise in the luteal than follicular phase (47.2 +/- 5.8 vs. 39.3 +/- 5.1 U/ml, respectively). The insulin-to-glucose ratio (I/G) was calculated and also showed significant changes. The I/G ratio was greater in the luteal than in the follicular phase at 0 min (6.5 +/- 0.4 vs. 5.3 +/- 0.6 mU/mmol, respectively). These data would suggest that in eumenorrheic women the menstrual cycle impacts the insulin/glucose relationship at rest, but has no effect during exercise. Whether the mechanism of the resting effect is due to changes in pancreatic and/or target tissue functions in unclear. Verf.-Referat