In older adults with subclinical hypothyroidism, treatment with levothyroxine provided no apparent benefit, a recent study found. The double-blind, randomized, placebo-controlled, parallel-group trial included 737 adults aged ≥65 years who had persisting subclinical hypothyroidism. 368 patients (mean age 74.4 years) were assigned to receive levothyroxine, with dose adjustment according to the thyrotropin level; 369 patients received placebo with mock dose adjustment. Researchers found:
- Mean (±SD) thyrotropin level was 6.40±2.01 mIU per liter at baseline; at 1 year, this level had decreased to 5.48 mIU per liter in the placebo group, as compared with 3.63 mIU per liter in the levothyroxine group (median dose of 50 μg).
- No differences were observed in the mean change at 1 year in the Hypothyroid Symptoms score or the Tiredness score.
- No beneficial effects of levothyroxine were seen on secondary-outcome measures.
- Adverse events were minimal.
Stott DJ, Rodondi N, Kearney PM, et al. Thyroid hormone therapy for older adults with subclinical hypothyroidism. N Engl J Med. 2017;376:2534-2544. doi:10.1056/NEJMoa1603825.
Subclinical hypothyroidism is defined as an elevated TSH with a normal serum free thyroxine level (T4). The TSH in subclinical hypothyroidism is usually in the 4.6–10 mIU per liter range. It is a commonly encountered clinical problem, with a prevalence of 8-18% in those aged >65 years.1 It is often difficult to determine if someone is symptomatic because many of the symptoms of hypothyroidism, such as fatigue, are common and not specific to thyroid disease. Often, subclinical hypothyroidism resolves over time, as was evidenced in this study; approximately 60% of patients who initially had an elevated TSH had normal TSH on repeat testing, and were excluded from the trial. This study informs our clinical practice and suggests that for older patients with subclinical hypothyroidism, the first step in our evaluation should be to repeat the TSH, as it often will revert to normal. For those with persistently elevated TSH, they may be followed over time to see if they develop overt hypothyroid disease with low free T4. But for those with a TSH below 10 mIU/liter, treatment with thyroid replacement seems to have little benefit. —Neil Skolnik, MD
- Canaris GJ, Manowitz NR, Mayor G, Ridgway EC. The Colorado Thyroid Disease Prevalence study. Arch Intern Med. 2000;160:526-34.