Although studies have examined the relationship between thyroid disorder (TD) and type 1 diabetes mellitus (T1DM), the information on TD and type 2 diabetes mellitus (T2DM) is limited, say researchers from Shahid Beheshti University of Medical Sciences and Aja University of Medical Science in Tehran, Iran, who report on an 11-year follow-up from the Tehran Thyroid Study. However, undetected TDs may compromise metabolic control of patients with diabetes mellitus (DM), impaired glucose tolerance, or impaired fasting glucose, the researchers point out. Undetected TDs also may increase the risk of cardiovascular diseases. And DM and prediabetes can affect thyroid tests.
The researchers evaluated 435 patients with DM, 286 with prediabetes, and 989 healthy controls. They conducted follow-up assessments every 3 years. About 19% of both the diabetic and prediabetic groups had TD, as did about 14% of the healthy controls. However, after adjusting for age, sex, smoking, blood pressure, body mass index, thyroid peroxidase antibody (TPOAb), thyrotropin (TSH), insulin resistance index, triglycerides, and cholesterol, no significant difference was found among the 3 groups. The mean incidence of TD was 14, 18, and 21 per 1000 patients per year in patients with DM, prediabetes, and healthy controls, respectively.
As in other studies, subclinical hypothyroidism and clinical hyperthyroidism were the most and the least common TD in patients with DM. Baseline TSH > 1.94 mU/L was predictive of TD with 70% sensitivity and specificity and had better predictive value than TPOAb . The researchers say conducting screening tests in all patients is not recommended except in those with TPOAb ≥ 401 U/mL or TSH > 1.94 mU/L.
Gholampour Dehaki M, Amouzegar A, Delshad H, Mehrabi Y, Tohidi M, Azizi F. PLoS One. 2017;12(10): e0184808.