Endocrine Abstracts

The relationship between subclinical hypothyroidism (SH) and cardiovascular (CV) risk is still matter of debate. While the key-role of thyroid hormones in modulation of several atherosclerotic factors is well established, the mechanisms of TSH’s action on CV system are still largely unknown.

In adults with SH a pattern of CV abnormalities (dyslipidemia, insulin resistance, endothelial and diastolic dysfunction) has been observed even in mild SH cases with TSH between 4.5 and 10 mU/L.

However, a positive effect of levo-thyroxine (L-T₄) therapy on CV morbidity and survival rates has not been clearly demonstrated although there are some evidence indicating an improvement in the lipid profile and left ventricular function.

It is well known that risk factors accelerating the development of atherosclerotic disease begins in childhood and may be predictive of CV risk in adulthood. Whether SH in children predisposes to adverse CV outcomes in adulthood is still unclear. Data on children are scanty and most of the studies are limited by the small number and the heterogeneity of the populations studied and by the presence of several confounding factors, as obesity and autoimmunity, making the evaluation of the direct impact of SH on CV risk difficult.

Recent data from a selected population of subjects with mild long-lasting idiopathic SH suggested that untreated SH children may develop a cluster of subtle metabolic abnormalities as increased abdominal adiposity and slight alterations in lipid profile and homocysteine levels. The clinical significance of these changes as early steps in initiation of atherogenesis is difficult to establish.

Therefore, although further studies evaluating the long-term CV consequences of childhood-onset SH and the effect of L-T₄ therapy are still to be made, the evidences available suggest that these children should be carefully monitored for metabolic complications that may expose them to an higher risk of future CV diseases.