Thyroid Function and Metabolic Syndrome: A Population-Based Thyroid Study

Abstract

The impact of thyroid dysfunction in subclinical ranges on metabolic syndrome (MetS) is not well known. The aim of the present study is to evaluate the association of thyroid dysfunction with MetS and its components. In the cross-sectional population-based Tehran Thyroid Study, out of 5 786 randomly selected participants, aged≥20 years, subjects with thyroid nodules and cancer or any severe systemic disease, those who were pregnant and those using thyroid medication were excluded, leaving 5 422 subjects to be investigated. Body weight, waist circumference, and blood pressure were measured. Fasting blood glucose and concentrations of lipids and lipoproteins, free T4, and TSH were assayed. Mean age of the participants was 40.3±14.4 of whom 101 (2%) had overt hypothyroidism, 294 (5%) subclinical hypothyroidism, 82 (2%) overt hyperthyroidism, and 178 (3%) had subclinical hyperthyroidism; 1 704 (32%) had MetS. Clinically hypothyroid subjects had the highest prevalence of MetS (41.6%), abdominal obesity (45%), and hypertriglyceridemia (58%) compared to other groups (p<0.05). Significant odds ratio for prevalent MetS was observed only in clinically hypothyroid men [OR: 2.9, 95% CI: 1.04, 8.4, p=0.04]. In women, the association between overt hypothyroidism and MetS was marginally significant only in the crude model [OR: 0.068, 95% CI (0.97-2.42), p=0.06]. There was higher risk of Mets in subclinically hypothyroid subjects, aged>50. Overt and subclinical hyperthyroidism had significantly higher odds of hyperglycemia in men and women after full adjustment for age, smoking, and BMI. Overt hypothyroidism and subclinical hypothyroidism especially in the elderly could be associated with MetS. Hyperthyroidism may induce hyperglycemia.

Raised TSH is associated with endothelial dysfunction in Metabolic Syndrome: A case control study

“…The study done by Mehran et al showed that some cases of Met S have thyroid abnormalities and mean TSH levels were higher in cases of Met S with sub clinical hypothyroidism as compared to Met S cases without sub clinical hypothyroidism [13]. This finding is very similar to our findings with larger sample size and more statistically significant results, however their study is cross-sectional and no assessment of endothelial dysfunction has been done.…”

Thyroid Stimulating Hormone Within the Reference Range is Associated with Visceral Adiposity Index and Lipid Accumulation Product: A Population-Based Study of SPECT-China

“…Thyroid hormones affect lipid and glucose metabolism, blood pressure, and obesity, all of which are associated with various cardiometabolic status [1][2][3]. Recent studies have demonstrated that the thyroid stimulating hormone (TSH) levels within the reference range were associated with obesity, lipid profile, and insulin resistance (IR) independent of thyroid function, which potentially modulates the cardiovascular conditions [4][5][6].…”

Association of serum free thyroxine and glucose homeostasis: Korea National Health and Nutrition Examination Survey

“…Christy et al [51] found that HbA1c levels to be higher in patients with hypothyroidism, but this study included patients with anaemia. Other population-based studies have demonstrated the association between dysglycaemia and FT4 levels, but not with HbA1c levels [44,52]. Our study is the first community-based study that investigated the association of HbA1c levels with FT4 levels in euthyroid healthy subjects.…”