Glycemic Control During the Menstrual Cycle in Women With Type 1 Diabetes: Performance of an Automated Insulin Delivery System

INTRODUCTION: Scientific evidence on the impact of the female hormonal cycle on glycemic control in type 1 diabetes (T1D) remains limited. This study aimed to evaluate variations in glycemic control and insulin requirements throughout the menstrual cycle in women with T1D using an automated insulin delivery (AID) system. MATERIALS AND METHODS: An observational cohort study was conducted in women with T1D using the MiniMed 780G AID system. Continuous glucose monitoring (CGM) and insulin delivery data were analysed and compared between the late luteal phase (LLP) (Days -7 to -1) and the early follicular phase (EFP) (Days 1-7) across up to three cycles per participant. RESULTS: ). During the LLP, participants showed a lower percentage of time in range (%TIR: 80.7% vs. 82.7%, p < 0.05) and higher time above range (%TAR: 17.3% vs. 14.6%, p < 0.01) and mean glucose (141 vs. 135 mg/dL, p < 0.01). In contrast, % time below range (%TBR) was higher during the EFP (2.8% vs. 2.0%, p < 0.01). The total daily insulin dose (TDD) increased during the LLP (33.1 vs. 32.0 units, p < 0.05), mainly due to higher prandial insulin (19.5 vs. 18.6 units), without significant differences in basal or autocorrection doses. CONCLUSIONS: Women with T1D using an AID system demonstrated phase-dependent differences in glycemic control, with lower time in range and greater hyperglycemia during the LLP and a higher susceptibility to hypoglycemia during the early follicular phase, accompanied by higher prandial insulin requirements.