Effect of Menstrual Cycle on Glycemic Outcomes and Insulin Requirements in Women with Type 1 Diabetes Who Are Users of Advanced Hybrid Closed-Loop Systems

Purpose: It has been previously described that some women with type 1 diabetes (T1D) may experience changes in glucose levels in relation to their menstrual cycle. However, whether an advanced hybrid closed-loop system (AHCL) can mitigate these cycle-dependent changes is yet to be determined. Methods: This study is a prospective analysis of a cohort of premenopausal women with T1D with spontaneous menstrual cycles who are users of an AHCL system 780G Medtronic^®. Three consecutive cycles were analyzed for each patient, and each cycle was divided into three phases (menstrual, luteal, and rest of cycle phase). Results: Fifteen subjects were included. Mean age was 38 ± 7.6 years, HbA1c was 7.12 ± 0.7%, and diabetes duration was 21 ± 13.7 years. Mean glucose was higher in the luteal phase compared to the menstrual period (<i>p</i> = 0.029 luteal vs. menstrual) and the rest of the cycle (<i>p</i> = 0.018 luteal vs. rest of cycle). The time in range (TIR) was lower in the luteal phase compared to the rest of cycle phase (<i>p</i> = 0.015 luteal vs. rest of cycle). The time below range (TBR) was significantly higher in the menstrual compared to the luteal phase (<i>p</i> = 0.007 luteal vs. menstrual). Daily insulin requirements were higher in luteal phase compared to rest of cycle (<i>p</i> = 0.017 luteal vs. rest of cycle). Conclusions: A higher mean glucose and lower TIR, despite a higher total insulin dose, was observed in the luteal phase. A higher TBR was observed in the menstrual phase. However, AHCL with 780G Medtronic^® achieves a TIR of almost 70% in all cycle phases.