Subclinical Hypothyroidism Tied to Increased Risk of Heart Disease Events, Deaths

Now that firmer data are established, the questions of screening and treatment remain to be answered, Dr. Rodondi said in the interview. Population-based screening is not warranted, but screening might someday be useful in specific groups – older patients, for example.

“Subclinical hypothyroidism is a very common finding, especially among older patients, with a prevalence of about 5% at age 50 [years] and 10% by age 65. But if we do screen these patients, and find abnormal levels, what do we do? At this point, we still don’t know,” he noted.

He also pointed out that there is no institutional support for any screening test without evidence that treatment can improve outcomes. “This is why we need an intervention trial,” he said. In fact, he and his colleagues are planning such a trial. Coauthor Dr. Douglas Bauer of the University of California, San Francisco, has secured a National Institutes of Health grant to begin its planning.

“It is likely to randomize older adults with subclinical hypothyroidism [to treatment or none] and examine not only cardiovascular disease, but musculoskeletal and cognitive outcomes as well,” Dr. Rodondi said.

In the meantime, physicians will still be left to weigh the existing evidence and apply it to each individual patient in making treatment decisions. “If a patient has a TSH above 10 mIU/L, we probably should be concerned that this person is at increased risk,” Dr. Rodondi said. “Our meta-analysis did not prove that it’s useful to treat that patient, but it is now clear that the person is likely to have a worse outcome than someone with a normal or near-normal TSH.”

Commenting on the study, Dr. Hossein Gharib said that it “confirms what is already known and applied by clinical endocrinologists – that a TSH of more than 10 mIU/L is clearly bad for the heart.” Furthermore, “it emphasizes that a borderline TSH between 5 and 10 mIU/L can also be bad, especially in a patient with other risk factors, such as antithyroid antibodies, goiter, hyperlipidemia, or pregnancy. Most clinical endocrinologists in the U.S. and in Europe would choose to treat these patients with thyroxine.”

Dr. Gharib’s personal practice “has been, and will continue to be, to favor treatment for these patients over no treatment.” Most clinical endocrinologists would agree in favor of treating a patient with a TSH of 6-10 mIU/L, he added, “once it has been confirmed on two separate occasions and in the presence of these other risk factors.”

A treatment trial such as the one Dr. Rodondi describes “will answer some of the concerns that still persist and is certainly desirable,” said Dr. Gharib, professor of medicine at the Mayo Clinic, Rochester, Minn. But until then, individual clinical judgment should override any blanket recommendations.

The study was sponsored by the National Institutes of Health. None of the authors reported any financial conflicts.