Endocrine Abstracts

: A link between thyroid dysfunction and diabetes mellitus exist. Uncertainties on the role of glycemic variability on thyroid hormones and TSH concentrations still persist. We want to evaluate the influence of glycemic variability on thyroid hormones and TSH concentrations in patients with type 1 diabetes (T1DM). 77 patients with T1DM on insulin therapy without thyroid dysfunction and 100 healthy controls were evaluated for basal glucose concentrations, HbA1c, thyroid hormones and TSH levels. Glucose variability was investigated through the standard deviation of blood glucose (BGSD) readings and through the mean amplitude of glycemic excursions (MAGE) and continuous overlapping net glycemic action (CONGA), the low (LBGI) and high (HBGI) blood glucose indices. The links between TSH, thyroid hormones, glycemia and HbA1c were studied in patients and in controls, whereas those between TSH, thyroid hormones and indices of glucose variability only in patients. All subjects had TSH, thyroid hormones and thyroid antibodies in the normal range. No correlations were found in T1DM patients between free thyroid hormones and glycemic values, HbA1c and indices of glucose variability, while an inverse correlation was observed between TSH levels and glycemic values (r=−0.4; P=0.02), CONGA index (r=−0.3; P=0.04) and HBGI (r=−0.3; P=0.05) but not with HbA1c (r=−0.1; P=0.47). No significant correlations of TSH and thyroid hormones with glycemia and HbA1c were observed in controls. In T1DM patients was found an inverse correlation between TSH and glycemic variability with direct action of glycemic excursions on TSH secretion disengaged from variations of thyroid hormone concentrations. The study of thyroid function (TSH concentrations) in these patients should be made by multiple samples on patients in euglycemic state to avoid underestimation or overestimation of thyroid dysfunction due to a misdiagnosis of euthyroidism or dysthyroidism with consequent inappropriate therapy.