Subclinical hyperthyroidism and cardiovascular manifestations: a reevaluation of the association

Subclinical hyperthyroidism (SH) has been reported associated with atrial fibrillation (AF), heart failure (HF) and coronary heart disease events, including mortality. An expert opinion indicates that AF is the possible link between SH and the other important cardiovascular (CV) manifestations. We analyzed the data of three recent studies including 60,883 subjects of whom 2,284 SH patients. In these subjects, the ratio between the AF events and each of the other above reported CV events varied from 0.14 to 0.4 in SH and from 0.2 to 2.4 in euthyroidism (ET). The general pattern of this ratio in 6 comparisons performed was not significantly higher for SH than ET. This data suggest that AF is not the major link between SH and the related CV manifestations. We suggest that a further link to be considered is the higher frequency of the early atherosclerosis manifestations such as carotid intima media thickness or carotid integrated back scatter, observed in SH. This atherogenic effect of SH can affect the occurrence of all the above clinical CV manifestations.