Elevated Serum Thyrotropin in Thyroxine-Treated Patients with Hypothyroidism Given Sertraline

To the Editor: Patients with hypothyroidism and organic depression may need both levothyroxine and antidepressant drug therapy. In nine levothyroxine-treated patients with hypothyroidism (Patients 1 through 9) who were treated with sertraline (Zoloft, Pfizer), we found elevated serum thyrotropin concentrations, indicative of a decrease in the efficacy of levothyroxine (Table 1). In addition, in two other levothyroxine-treated patients with thyroid cancer whose serum thyrotropin concentrations had been deliberately suppressed (Patients 10 and 11), the values rose into the normal range during sertraline therapy. The value for the serum free thyroxine index decreased in all patients in whom it was measured . . .