Is thyroid-stimulating hormone within the normal reference range a risk factor for atherosclerosis in women?

The relationship between overt hypothyroidism and cardiovascular risk has been well documented and some data also suggest an association between cardiovascular risk and subclinical hypothyroidism. The aim of our study was to investigate, in a large cohort of euthyroid women, the association of thyroid stimulating hormone (TSH) within the normal reference range with cardiovascular risk factors. The study was carried out on 744 women with normal thyroid function (TSH 0.3-4.9 μU/mL). Women with TSH above the median (≥2.1 μU/mL) were more obese, had greater waist girth, were more hypertensive and had higher levels of total cholesterol (TC), serum triglycerides (TG), blood sugar (BG) and lower levels of HDL-cholesterol (HDL-C) than women with TSH below the median. TSH was significantly correlated with body mass index (BMI), waist circumference, BG, TG, TC, HDL-C and hypertension. Multiple backward stepwise regression analysis with age, waist circumference and TSH as independent variables confirmed the strong association of TSH with BG, TG, HDL-C and hypertension. A total of 205 patients (28%) fulfilled the definition criteria of the metabolic syndrome and the prevalence of metabolic syndrome was significantly greater in patients with TSH above than in patients with TSH below the median. Results of logistic analysis, including age and TSH as predictor variables, confirmed the association of TSH with metabolic syndrome.The results of this study suggest that TSH in the upper limits of the reference range (above 2.1 μU/ml) is associated with a less favourable cardiometabolic profile and consequently with a higher risk of developing cardiovascular diseases.