Risk factors for cardiovascular disease in subclinical hypothyroidism

Subclinical hypothyroidism (SH), defined as an increased serum thyrotropin (TSH) level and normal plasma-free thyroid hormones' concentrations, is common in the general population, in particular, among elderly women. Its prevalence ranges from 4 to 15% and up to 20% among females aged > 60 year. Although SH has been associated with atherosclerotic cardiovascular disease (CVD), it is acknowledged that the high prevalence of dyslipidemia in elderly people is considered a common biochemical condition. Therefore, whether SH is associated with a higher risk for CVD is still controversial. At the moment, no consensus exists on the clinical significance and treatment of the mild form of thyroid failure, although available data suggest that only patients with plasma TSH levels above 10 mU/L may have an increased risk of CVD. However, treatment of SH in older individual requires special consideration with regard to thyroid hormone replacement therapy and expected clinical outcomes, since the increase of TSH observed in this population may represent a physiological process. It is likely that age affects TSH levels, and some studies suggest that modified reference limits for elderly populations should be considered in the diagnosis of mild thyroid failure.