O-61: The menses study: impact of menstrual cycle on glycaemic control in 465 menstrual cycles from 153 adolescents with type 1 diabetes
C Nobili, G Prandi, B Bombaci, E Morotti, C A Piona, S Passanisi, G Gay, A Di Pisa, E Caiazza, D Tinti, M Trada, F Lombardo, C Maffeis, L de SanctisAbstract
Introduction
Hormonal fluctuations during the menstrual cycle affect insulin sensitivity, yet their impact on CGM outcomes in adolescents with type 1 diabetes (T1D) is poorly characterised. Whether automated insulin delivery (AID) compensates for cycle-related variability is not estabished in big cohorts.
Objectives
To assess the effect of menstrual cycle phase on glycaemic control in adolescent girls with T1D using AID or multiple daily injections (MDI).
Methods
Cross-sectional multicentre study (3 Italian centres). Adolescents (12–20 y) with T1D, CGM use ≥1 year, HbA1c <10% were enrolled. Participants reported dates of recent menstrual periods. Each sensor-day was mapped into phases: menses onset (day 0), early/mid follicular, peri-ovulatory, mid/late luteal. A questionnaire assessed perceived glycaemic changes and insulin-dose adjustments during menses. Linear mixed models tested the effect of phase, therapy (AID vs MDI), and their interaction, adjusting for age, diabetes duration, BMI-SDS, and HbA1c.
Results
153 adolescents contributed 465 menstrual cycles (~13,950 cycle-days). Menstrual phase significantly affected TIR (p<0.001), with the lowest values at menses onset and mid-luteal phase (Figure). TIR amplitude across phases was 2.0 pp in AID vs 5.6 pp in MDI. On onset day, TIR dropped by 1.6 pp vs late luteal in AID users (p=0.012). The phase effect differed by therapy (p<0.001): MDI showed larger luteal worsening. 77% of MDI vs 51% of AID users reported perceived hyperglycaemia during the luteal phase (p=0.014), and 57% vs 34% increased insulin doses (p=0.023).
Conclusions
The menstrual cycle significantly affects glycaemic control in adolescents with T1D, with the worst values at menses onset and during the luteal phase. Integrating cycle-phase awareness into patient education and AID algorithms may reduce this gender-specific gapin diabetes care.