COUNTER-REGULATORY RESPONSE TO HYPOGLYCEMIA IN THE FOLLICULAR AND LUTEAL PHASES OF THE MENSTRUAL-CYCLE

Objective: To assess whether the phase of the menstrual cycle influences the counter-regulatory response to hypoglycemia. Design: Prospective randomized euglycemia-hypoglycemia clamp studies in the follicular and luteal phases of the menstrual cycle in the same woman. Settings: Clinical Research Center, Yale University School of Medicine. Patients: Eight regularly menstruating nonobese women. Main Outcome Measures: Counter-regulatory hormonal response to hypoglycemia-epinephrine, norepinephrine, glucagon, cortisol, GH, and PRL; glucose homeostasis: rates of whole-body glucose appearance and utilization, and the rate of hepatic glucose production. Results: In the follicular and luteal phases of the cycle fasting glucose levels (88 +/- 1 and 85 +/- 2 mg/dL, mean +/- SEM, respectively; conversion factor to SI units, 0.05551), basal glucose turnover (2.37 +/- 0.20 and 2.63 +/- 0.13 mg/kg per minute), basal insulin levels (10 +/- 1 and 9 +/- 1 mu U/mL; conversion factor to SI units, 6.0), and insulin levels during the clamp study (53 +/- 3 and 45 +/- 4 mu U/mL) were not significantly different. During the euglycemic phase of both studies, glucose utilization rose twofold (to 4.73 +/- 0.31 and 4.39 +/- 0.31 mg/kg per minute): hepatic glucose production was suppressed; and counter-regulatory hormones remained unchanged. Induction of hypoglycemia produced increases in the concentrations of counter-regulatory hormones that were indistinguishable in both phases of the cycle. Similarly, the increase in hepatic glucose production provoked during hypoglycemia was similar in each phase of the cycle (1.20 +/- 0.24 and 1.28 +/- 0.36 mg/kg per minute). Conclusion: The counter-regulatory hormonal response to hypoglycemia, as well as the metabolic sequelae of these hormonal changes, are similar in the follicular and luteal phases of the menstrual cycle.