A study of changes in insulin requirements related to the menstrual cycle in Japanese women with type 1 diabetes using the advanced hybrid closed-loop system

AIMS/INTRODUCTION: In type 1 diabetes (T1D), insulin requirements and glycemic control may vary across the menstrual cycle. We examined phase-related differences in insulin requirements, glycemic metrics, and recorded carbohydrate amounts in women using an advanced hybrid closed-loop (AHCL) system and their associations with menstrual symptoms and premenstrual dysphoric disorder (PMDD) screening status. MATERIALS AND METHODS: Fifteen premenopausal women with T1D using the MiniMed 780G without hormonal therapy were analyzed. Cycles with ≥2 eligible days (SmartGuard ≥70%) in both early follicular (d1-7) and late-luteal (d-7 to -1) phases were included. Phase differences were assessed using linear mixed-effects models. Associations between phase-related changes and menstrual symptom scores and PMDD screening status were evaluated using Spearman correlation and the Mann-Whitney U test, respectively. RESULTS: Eighty cycles were analyzed. Compared with the early follicular phase, the late-luteal phase showed a higher total daily insulin dose (49.2 ± 3.7 vs 45.1 ± 3.7 U/day), basal insulin dose, total bolus insulin, and recorded carbohydrate amount (197.9 ± 18.2 vs 186.1 ± 18.2 g/day), with lower Time in Range (70.0 ± 3.2% vs 72.9 ± 3.2%) and higher Time above Range (TAR). Most phase-related differences persisted after adjustment for recorded carbohydrate amount. No clear associations between menstrual symptom scores or PMDD screening status and phase-related changes were detected. CONCLUSION: During AHCL therapy, insulin requirements increased and glycemic control modestly worsened in the late-luteal phase. No clear associations between phase-related metabolic changes and menstrual symptom scores or PMDD screening status were detected in this small cohort.