Thyroid axis activity and suicidal behavior in depressed patients

SummaryThe aim of this study was to investigate the relationship between suicidal behavior and hypothalamic–pituitary thyroid (HPT) axis activity in depressed patients. The serum levels of thyrotropin (TSH), free thyroxine (FT4), and free triiodothyronine (FT3) were evaluated before and after 0800 and 2300 h thyrotropin-releasing hormone (TRH) challenges, on the same day, in 95 medication-free DSM-IV euthyroid major depressed inpatients and 44 healthy hospitalized controls. Compared to controls: (1) patients with a positive suicide history (PSH; n = 53) showed lower basal FT4 (at 0800 h: p < 0.005; at 2300 h: p < 0.03), but normal FT3 levels, while patients with a negative suicide history (NSH; n = 42) showed normal FT4 and FT3 levels; (2) TSH responses to TRH (ΔTSH) were blunted in NSHs (at 0800 h: p < 0.03; at 2300 h: p < 0.00001), but not in PSHs; (3) both NSHs and PSHs showed lower ΔΔTSH values (differences between 2300 h-ΔTSH and 0800 h-ΔTSH) (p < 0.000001 and p < 0.003, respectively). Compared to NSHs, basal FT4 levels were reduced in PSHs (at 0800 h: p < 0.002; at 2300 h: p < 0.006). HPT parameters were not significantly different between recent suicide attempters (n = 32) and past suicide attempters (n = 21). However, compared to controls, recent suicide attempters showed lower 2300 h-ΔTSH (p < 0.04) and ΔΔTSH (p < 0.002) values, and lower basal FT4 values (at 0800 h: p < 0.006; at 2300 h: p < 0.02). Our results, obtained in a large sample of depressed inpatients, indicate that various degrees of HPT axis dysregulation are associated with the history of suicide.