Hormone replacement therapy in older adults with subclinical hypothyroidism is tied to higher mortality compared with no treatment, a large study finds.
Patients who have subclinical hypothyroidism, a mild or early form of thyroid disease, typically receive thyroid hormone replacement with levothyroxine. These patients show modest elevations in thyroid-stimulating hormone (TSH).
But in older patients, elevated TSH may not reflect early hypothyroidism. In fact, the investigators’ earlier research suggests that mild TSH elevations are an adaptation to age-related health changes – not thyroid disease, said Jennifer Mammen, M.D., Ph.D., from Johns Hopkins University.
“As a result, some of these older people may be receiving inappropriate or excessive thyroid hormone therapy, treatment that may counteract important adaptations needed for healthy aging.”
In the current study, the researchers looked at the effects of levothyroxine therapy on survival in adults ages 65 and older during one-year intervals from 2003 to 2018. Data was drawn from the Baltimore Longitudinal Study of Aging, and the analyses adjusted for demographic and health factors.
The use of thyroid hormone increased mortality risk by 60% year over year. And when the analysis was limited to compare individuals with normal TSH levels to those on thyroid hormone with normal TSH levels, participants taking hormones were found to have almost double the odds of dying compared with the untreated group.
“Our work supports the growing calls to use age-specific TSH reference intervals to determine the threshold for thyroid hormone treatment,” Mammen concluded. “We advocate being cautious and conservative when considering thyroid hormone treatment.”