Irregular heartbeat linked to higher thyroid hormone levels

(American Heart Association) Individuals with higher levels of thyroid hormone (free thyroxine or FT4) circulating in the blood were more likely than individuals with lower levels to develop irregular heartbeat, even when the levels were within normal range. Blood levels of thyroid-stimulating hormone (TSH), which regulates the production of thyroid hormones and is primarily measured in clinical practice to assess thyroid function, however, were not associated with an increased risk of irregular...