Petah Tikva, Israel—Physicians who prescribe levothyroxine to elderly patients with subclinical hypothyroidism might think they are doing them a favor. In reality, according to a new study, the opposite might be true.

A presentation at ENDO 2018, the recent 100th annual meeting of the Endocrine Society in Chicago, suggests that treating those patients with the commonly prescribed drug for underactive thyroid actually puts them at increased risk of dying.

“In patients who are 65 years of age or above with subclinical hypothyroidism and thyroid-stimulating hormone (TSH) <10 mIU/L (milli-international units per liter), treatment with levothyroxine is associated with significantly increased mortality,” explained lead author Joseph Meyerovitch, MD, professor and senior physician at the Schneider Children’s Medical Center of Israel in Petah Tikva.

Meyerovitch recommended that the results of the study be considered before patients aged 65 years or older with subclinical hypothyroidism and TSH values under 10 mIU/L are treated with the common drugs.

Noting that whether subclinical hypothyroidism should be treated with levothyroxine is a matter of debate, particularly in the elderly, the study team analyzed older patients with TSH levels between 4.2 and 10 mIU/L who died during the years 2012 through 2016. Those cases were matched with a control group of patients who survived based on age, gender, Charlson comorbidity index, TSH testing date, follow-up duration, and TSH quartile.

In addition, use of levothyroxine was compared between the groups, excluding all patients with known thyroid disease or those who had received antithyroid medications or glucocorticoids in the year before they were tested for TSH.

Results indicate that treatment with levothyroxine was linked with significantly increased mortality (hazard ratio = 1.19). Factors found to be associated with mortality were age, senile dementia, congestive heart failure, chronic renal failure, and a history of cerebrovascular disease.

Femoral fractures and atrial fibrillation following initiation of levothyroxine therapy were not more prevalent in individuals who died during the follow-up period, however.

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