LAUSR

Levothyroxine is one of the most commonly prescribed drugs. A common reason for levothyroxine treatment on patients with subclinical hypothyroidism are depressive symptoms. A meta-analysis of four RCTs (n = 278) found no benefit of levothyroxine therapy on depressive symptoms. However, the confidence interval does not exclude a small clinical benefit. We aim to assess the effect of levothyroxine therapy for depressive symptoms in patients with subclinical hypothyroidism using data from a RCT with more than 400 adults. The TRUST trial was a double-blind, randomized, placebo-controlled trial involving adults aged ≥65y with subclinical hypothyroidism (elevated TSH levels (4.6-19.9 mU/L) and free thyroxine within the reference range). The outcome was depressive symptoms after 12 months based on the Geriatric Depression Scale (GDS-15), a 15-item questionnaire (range: 0 to 15, higher scores indicate more depressive symptoms, minimal clinical important difference: 2). The multivariable linear regression model was adjusted for levothyroxine starting dose, sex, site, and GDS-15 baseline score. 425 Swiss and Dutch adults with subclinical hypothyroidism were randomised (mean age 75y, 56% female). The mean (SD) TSH was 6.6 (2.1) mU/L at baseline and after 12 months decreased to 3.8 (2.3) mU/L in the levothyroxine group vs 5.9 (2.7) mU/L in the placebo group. At baseline, the mean GDS-15 score was 1.3 (1.9) in the levothyroxine group and 1.0 (1.6) in the placebo group. The mean GDS-15 score at 12 months was 1.4 (2.1) in the levothyroxine and 1.1 (1.7) in the placebo group with an adjusted between-group difference of 0.2 for levothyroxine vs. placebo (95% CI:-0.1 to 0.5; p = 0.29). In this by far largest RCT on the topic, levothyroxine therapy did not confer a benefit for depressive symptoms. Consequently, our results do not support the practice of prescribing levothyroxine for depressive symptoms when they co-occur with subclinical hypothyroidism. Levothyroxine has no benefit on depressive symptoms in patients with subclinical hypothyroidism. Levothyroxine prescription to patients with subclinical hypothyroidism and depressive symptoms should be reconsidered.