New insights on diabetes in Turner syndrome: results from an observational study in adulthood

OBJECTIVE: To explore the characteristics of diabetes mellitus in adults with Turner syndrome. DESIGN: Observational study consisting of a prospective phase after the access of adults with Turner syndrome to the Endocrinology Unit (median period of follow-up 15.6, interquartile range: 12.0-24.5 months) and a retrospective collection of data from the diagnosis of Turner syndrome until the time of access to the Endocrinology Unit. A total of 113 Italian Turner syndrome patients were included in the study. During the prospective phase of the study, each patient underwent physical examination, fasting blood sampling, and an oral glucose tolerance test on a yearly basis. Oral glucose tolerance test was used to perform the diagnosis of diabetes mellitus. RESULTS: Before access to the Endocrinology Unit, diabetes mellitus was diagnosed in two Turner syndrome patients. Another five cases of diabetes mellitus were diagnosed at the first access to the Endocrinology Unit, whereas seven new cases of diabetes mellitus were diagnosed during the prospective phase of the study. At the diagnosis of diabetes mellitus, only one patient had fasting glucose above 126 mg/dL, and only two had an HbA1c value >6.5% (48 mmol/mol). When compared to normo-glucose tolerant patients, the diabetic patients had a significantly lower insulin-to-glucose ratio at 30 and 60 min of the oral glucose tolerance test. In the regression analyses, only age was associated with the development of diabetes mellitus. CONCLUSIONS: This study confirms that diabetes mellitus is frequent in Turner syndrome and suggests that it is specific to the syndrome. In addition, this study demonstrates that oral glucose tolerance test is a more sensitive test than HbA1c for the diagnosis of diabetes mellitus in Turner syndrome.