Low serum thyrotropin concentrations as a risk factor for atrial fibrillation in older persons

A low concentration of the thyroid hormone thyrotropin in the blood of persons aged 60 or older may be an independent risk factor for atrial fibrillation (a type of irregular heartbeat). A large study of 2007 persons 60 years old and older followed up for 10 years revealed that those persons with low serum thyrotropin concentrations had three times the risk of developing atrial fibrillation as did persons with normal thyrotropin concentrations. Hyperthyroidism is known to be a risk factor for atrial fibrillation, but older persons with atrial fibrillation usually do not also have hyperthyroidism. Subclinical (too small to be detected easily) hyperthyroidism is known to occur in older persons, and it is marked by a low serum thyrotropin concentration in persons with otherwise normal serum thyroid hormone concentrations. Identifying risk factors for atrial fibrillation is important because it may lead to stroke and decreased heart output. Older persons with low serum thyrotropin concentrations should be monitored for signs of hyperthyroidism and atrial fibrillation. Such persons receiving thyroid hormone therapy should receive lower doses.