Levothyroxine provided no benefits in older patients with subclinical hypothyroidism in the first large randomized clinical trial of the treatment for this indication, which was presented at the annual meeting of the Endocrine Society.

An estimated 8%-18% of people aged 65 and older have subclinical hypothyroidism, which is defined as an elevated serum thyrotropin level and a serum free-thyroxine level within the reference range. The condition is considered to be a possible contributor to many problems affecting numerous physiologic systems including the vascular tree, the heart, the brain, skeletal muscle, and bone, said David J. Stott, MD, of the academic section of geriatric medicine, Institute of Cardiovascular and Medical Sciences, University of Glasgow.

Until now, randomized trials examining levothyroxine replacement therapy in this patient population have been small, underpowered, “and have yielded only limited evidence regarding the possible benefits and risks of treatment.” So investigators performed an international double-blind placebo-controlled trial comparing levothyroxine (368 adults) against matching placebo (369 adults) in community-dwelling people whose medical records indicated subclinical hypothyroidism. The results were presented at the meeting and simultaneously published online in the New England Journal of Medicine (2017 Apr 3. doi: 10.1056/NEJMoa1603825).

The mean age of the study participants was 74 years, and they were followed for a median of 18 months after initiating treatment. The active intervention did boost thyroid function as expected, compared with placebo.

The two primary outcome measures were change between baseline and 1 year in hypothyroid symptoms and in tiredness scores on the 100-point ThyPRO (Thyroid-Related Quality of Life Patient-Reported Outcome) measure. There were no significant differences between the two study groups in changes in either of these scores. The mean 1-year score for hypothyroid symptoms was 16.6 for levothyroxine and 16.7 for placebo, and the mean 1-year score for tiredness was 28.7 for levothyroxine and 28.6 for placebo.

Secondary outcomes also did not differ significantly between the two study groups, including general health-related quality of life; hand-grip strength (reflecting possible effects on skeletal muscle); executive cognitive function (reflecting possible effects on the brain); blood pressure, weight, body mass index, and waist circumference (reflecting possible effects on cardiovascular health); or activities of daily living. In addition, both fatal and nonfatal cardiovascular events were similar between the two study groups at 1 year and at extended 3-year follow-up.

Further analyses did not identify any subgroup of adults who benefited from active treatment. The lack of benefit extended across all older age groups, both genders, and all serum thyrotropin levels at baseline. In addition, all the sensitivity analyses confirmed the results of the main analysis.

Adverse events also were not significantly different between the two study groups. This included four serious adverse events of special interest: new-onset atrial fibrillation, heart failure, fracture, or osteoporosis. There also was no increase in symptoms of hyperthyroidism in the active-treatment group.


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