Low free-thyroxine levels are a risk factor for subclinical atherosclerosis in euthyroid hyperlipidemic patients.

Abstract

Patients displaying overt and subclinical hypothyroidism have more cardiovascular risk factors. Consequently, they are more likely to develop atherosclerosis and cardiovascular diseases. To analyze whether low free-thyroxine levels (FTL) would also be associated with atherosclerosis in euthyroid patients. We selected a group of 1434 healthy euthyroid male patients without known histories of thyroid disease and with levels of thyroid-stimulating hormone values within the normal range (mean 1.70+/-0.76 mUl/l, range 0.13-4.01 mUl/l). Mean age of these patients who had been referred for assessment of hyperlipidemia was 44.6 years and mean FTL was 14.25+/-3.06 pmol/l. We divided the population according to the degree of atherosclerosis in the carotid arteries. Mean age, body mass index, systolic blood pressure, cigarettes/day, blood level of glucose, cholesterol levels, and fibrinogen levels were significantly higher for the patients with atherosclerotic lesions whereas mean FTL was lower for patients with carotid atherosclerosis (P = 0.0002). The relationship between FTL and carotid atherosclerosis was independent from the following cardiovascular risk factors: age, hypertension, amount of excess weight, cholesterol level, fibrinogen level, smoking status, and presence versus absence of diabetes mellitus. Low FTL is a risk factor for atherosclerosis in male euthyroid hyperlipidemic patients.