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Thyroid and Heart - Association between mild thyroid dysfunction and cardiovascular risk

Cardiovascular disease is the foremost cause of premature death and the most common cause of hospital admission in western countries. At the same time, the death rate for cardiovascular disease has been falling in the last few years. Strategies for reducing risk factors have unequivocally played an important role in reducing mortality and morbidity, especially in people with recognized cardiovascular disease. Attention has particularly focused on discovering new, potentially important risk factors. Data on the prognostic impact of primitive mild thyroid dysfunction in patients with cardiac disease are, however, limited and somewhat conflicting.
The major finding of a new large prospective observational study performed on 3121 cardiac patients (mean follow-up 32 months) was that the concomitant presence of an unknown mild thyroid dysfunction is linked to an increased risk of mortality. After adjustment for several risk factors, the hazard ratio for cardiac death was higher in subclinical hypothyroidism (2.40, p=0.02), subclinical hyperthyroidism (2.32, p=0.02) and low-triiodothyronine syndrome (1.63, p=0.007) than in euthyroid patients. Moreover, analysis of subgroup of patients (i.e. ischemic and non-ischemic patients) showed that mild thyroid dysfunction increased the risk of death particularly in ischemic heart disease. The potential clinical impact of thyroid dysfunction on cardiac patients is quite important if one considers the high incidence of a mildly altered thyroid hormone pattern in the cardiac population (39% of total) as observed in our study. Altogether, the results of this observational prospective study also open the way to interesting pathophysiological interpretations and new therapeutical strategies. The observed negative prognostic impact of any form of mild thyroid dysfunction in cardiac patients reinforces the hypothesis that a normal thyroid status is essential for maintaining systemic and cardiovascular homeostasis; when persistently lost, increased whole-body and cardiovascular vulnerability is observed.

Iervasi G. et al., CNR Institute of Clinical Physiology, Research Campus - Pisa

in press su "Archives of Internal Medicine": 167(14), 23 July 2007

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