Subclinical hypothyroidism and the prevalence of the metabolic syndrome.

There is currently controversial data regarding the prevalence of MS among SCH patients. The aim of the study was to investigate the prevalence of MS in an adult population with SCH. A cross-sectional study was conducted among 6,998 adults in China. Epidemiological information and medical data were obtained (fasting plasma glucose, triglycerides, high density lipoprotein-C, and thyroid function). The IDF criteria were applied for the diagnosis of MS. SCH was defined as TSH more than 4.5 mIU/l with normal values for FT3 and FT4. Among the 6,560 participants, 21.5% were diagnosed with MS and 8.2% suffered from SCH. MS was found in 21.3% in the euthyroidism (EUT) group and in 25.7% in the SCH group (p<0.05). However, this difference between EUT and SCH in MS prevalence was not statistically significant after adjusting for age. Of note, the prevalence of MS increased with age. The proportions of systemic hypertension, hypertriglyceridemia, impaired fasting glucose, and low HDL-C were 86.7, 59.7, 45.1 and 65.9% in EUT while the corresponding values in SCH were 89.9, 63.8, 39.9 and 72.5%, respectively (the differences, however, did not reach statistical significance). The prevalence of high BP, high TG, elevated FBP, and low HDL-C as well as the percentage of patients fulfilling the IDF criteria for the metabolic syndrome are not significantly different among SCH and EUT after adjusting for age. Therefore, subclinical hypothyroidism appears not as an independent risk factor for the metabolic syndrome in this population.