First observations suggesting an association of diabetes and the menstrual cycle were made early in the history of insulin therapy in the 1940s, where cyclic changes in blood glucose concentrations were observed in seven girls with T1D prior to their menarche.31 Further studies from the 1990s and the early 2000s have found menstrual irregularities to occur more frequently in adolescents32 and adults with T1D.33,34 Insulin sensitivity in relation to the menstrual cycle was first investigated by hyperglycemic, hyperinsulinemic clamp studies in the 1990s. Here, INS is linked to type 1 diabetes mellitus.