Metabolic syndrome and its components are associated with increased thyroid volume and nodule prevalence in a mild-to-moderate iodine deficient area
Semra Ayturk, Alptekin Gursoy, Altug Kut, Cuneyd Anil, Asli Nar & Neslihan Bascil Tutuncu
Objective: The metabolic syndrome (MetS) is a cluster of metabolic abnormalities with insulin resistance (IR) as a major characteristic. It has been recently questioned that MetS and its related components are associated with functional and morphological alterations of thyroid gland. Aim of our study is to examine thyroid volume and nodule prevalence in patients with MetS in a mild-to-moderate iodine deficient area.
Design: Two hundred and seventy-eight patients with MetS were compared with 261 subjects without MetS. Serum thyroid-stimulating hormone (TSH), free T3 and T4, and the level of insulin resistance, estimated by the homeostasis model assessment for IR (HOMA-IR), as well as other MetS parameters were evaluated. Thyroid ultrasonography was performed in all participants. All thyroid nodules >1 cm underwent fine needle aspiration biopsy.
Results: TSH was significantly positively correlated with the presence of MetS diagnosis. Mean thyroid volume was higher in patients with MetS than in controls (17.5±5.5 vs 12.2±4.2 ml, P<0.0001). Thyroid nodules were more frequent in patients with MetS (50.4 vs 14.6%, P< 0.0001). Subjects with IR had increased thyroid volume and nodule formation. The odds ratio for the development of thyroid nodule in the presence of IR was 3.2. TSH as well as all MetS components were found to be independent predictors for thyroid volume increase. IR but not TSH was found to be correlated with thyroid nodule formation. Thyroid cancer was diagnosed in 3/38 patients with MetS (7.9%). No cancer cases were found in control subjects.
Conclusions: The results suggest that patients with MetS have significantly increased thyroid volume and nodule prevalence. The presence of IR contributed substantially to this increased risk. Our data provide the first evidence that IR is an independent risk factor for nodule formation in an iodine deficient environment.