Effects of long term treatment with sertraline (Zoloft) simulating hypothyroidism in an adolescent

A 16-year-old depressed adolescent, who had received sertraline treatment for the previous 18 months, developed insomnia, daytime somnolence and lack of energy. His thyroid function tests revealed low levels of total T4 with normal levels of free T4 and TSH, and a normal thyrotropin-releasing hormone (TRH) stimulation test. Discontinuing sertraline resulted in improved sleep and disappearance of daytime somnolence. Although daytime somnolence and low levels of total T4 can mimic hypothyroidism, in this case sertraline only displaced the bound-fraction of total T4 and was not associated with true hypothyroidism.