Subclinical Hypothyroidism Linked to CHF in Elderly

Abstract

Elderly patients with subclinical hypothyroidism have a higher rate of congestive heart failure than do those who are euthyroid, according to Dr. Nicolas Rodondi of the University of California, San Francisco, and his associates.Overt hypothyroidism is known to be associated with cardiovascular disease (CVD), but studies evaluating a possible link between subclinical hypothyroidism and CVD have produced conflicting results. The researchers conducted what they described as the first prospective study to assess the risk of heart failure (HF) events in subjects with subclinical hypothyroidism.The investigators assessed thyrotropin levels in 2,730 men and women aged 70–79 years who were participating in a large cohort study of aging. The subjects were followed for 4 years to determine whether these hormone levels were related to HF or other cardiovascular disease events.A total of 338 subjects (12.4%) were found to have subclinical hypothyroidism, defined as an elevated level of thyrotropin and a normal level of free thyroxine (T4). At follow-up, 178 subjects had HF events (Arch. Intern. Med. 2005;165:2460–6).Subjects with moderately to severely elevated thyrotropin levels (7.0 mIU/L or greater) had more HF events (35.0 per 1,000 person-years) than did those who were euthyroid (16.5 per 1,000 person-years). Each standard deviation increase of 4.0 mIU/L was associated with a 30% increase in HF events.This link was even stronger among subjects known to have had previous HF events. The rate of recurrent HF events was seven times higher in those with subclinical hypothyroidism than in those who were euthyroid.In contrast, subjects with mildly elevated thyrotropin (4.5–6.9 mIU/L) did not have higher rates of HF events.The results suggest further study is warranted to determine whether subclinical hypothyroidism causes heart failure or worsens existing heart failure, Dr. Rodondi and his associates said. Elderly patients with subclinical hypothyroidism have a higher rate of congestive heart failure than do those who are euthyroid, according to Dr. Nicolas Rodondi of the University of California, San Francisco, and his associates. Overt hypothyroidism is known to be associated with cardiovascular disease (CVD), but studies evaluating a possible link between subclinical hypothyroidism and CVD have produced conflicting results. The researchers conducted what they described as the first prospective study to assess the risk of heart failure (HF) events in subjects with subclinical hypothyroidism. The investigators assessed thyrotropin levels in 2,730 men and women aged 70–79 years who were participating in a large cohort study of aging. The subjects were followed for 4 years to determine whether these hormone levels were related to HF or other cardiovascular disease events. A total of 338 subjects (12.4%) were found to have subclinical hypothyroidism, defined as an elevated level of thyrotropin and a normal level of free thyroxine (T4). At follow-up, 178 subjects had HF events (Arch. Intern. Med. 2005;165:2460–6). Subjects with moderately to severely elevated thyrotropin levels (7.0 mIU/L or greater) had more HF events (35.0 per 1,000 person-years) than did those who were euthyroid (16.5 per 1,000 person-years). Each standard deviation increase of 4.0 mIU/L was associated with a 30% increase in HF events. This link was even stronger among subjects known to have had previous HF events. The rate of recurrent HF events was seven times higher in those with subclinical hypothyroidism than in those who were euthyroid. In contrast, subjects with mildly elevated thyrotropin (4.5–6.9 mIU/L) did not have higher rates of HF events. The results suggest further study is warranted to determine whether subclinical hypothyroidism causes heart failure or worsens existing heart failure, Dr. Rodondi and his associates said.