(DCP082) EFFECTS OF THE MENSTRUAL CYCLE PHASES ON SERUM ELECTROLYTE CONCENTRATIONS IN RESPONSE TO EXERCISE IN FEMALE PARTICIPANTS WITH TYPE 1 DIABETES

Background: Estrogen and progesterone fluctuations across the menstrual cycle can affect fluid and electrolyte balance. These effects on electrolyte concentrations may be more prominent in response to exercise. As for those with type 1 diabetes (T1D), significant knowledge gaps exist around changes in serum electrolyte concentrations in response to exercise with regards to the menstrual cycle phases. This is of particular importance in T1D as the risk of electrolyte imbalances can increase in tandem with the degree and duration of blood glucose changes, especially since cyclic changes in blood glucose levels and insulin sensitivity have been reported in females with T1D.

METHODS AND RESULTS: We compared the effect of a late-afternoon, moderate aerobic exercise (cycling at 50% of pre-determined VO2peak for 45 min) on serum concentrations of sodium, potassium, calcium, and magnesium between the early follicular and late luteal phases of the menstrual cycle in 9 female participants with T1D (mean±SD: age 30.2±9 years, A1C 7.4±0.7%, VO2peak 32.5±4.2 mL·kg-1·min-1) with regular menstrual cycles not using oral contraceptives.

In both phases, serum sodium, potassium, and calcium concentrations increased from pre to post exercise (time effect: p< 0.05) and decreased throughout the recovery (time effect: p< 0.05) but were not significantly different between the two phases either during exercise or recovery (phase effect: p>0.05). Serum magnesium concentration showed no significant effect of time or phase from pre to post exercise either during the late luteal or the early follicular phase (p>0.05). There was, however, a significant decrease in serum magnesium concentration during recovery in both phases (time effect: p< 0.05) but no significant effect of phase (p>0.05) [Figure 1 A-D].

Conclusion: The lack of significant differences in electrolyte concentrations between menstrual cycle phases suggests that the menstrual cycle may not have a significant effect on serum electrolytes during exercise of moderate intensity and duration. Future studies should consider the impact of longer or more intense exercise sessions at different temperatures on electrolytes in females with T1D during different phases of the menstrual cycle.