2566 – Chronobiological Thyroid Axis Activity and Suicidal Behavior in Depressed Patients

Abstract

Objectives:

The aim of this study was to investigate the relationship between suicidal behavior and chronobiological thyroid axis activity in depressed patients.

Methods:

The serum levels of TSH, were evaluated before and after 8 AM and 11 PM TRH challenges, on the same day, in 230 medication-free DSM-IV euthyroid major depressed inpatients and 50 healthy hospitalized controls.

Results:

Compared to controls: 1) patients with a recent suicide attempt (n = 71) showed lower TSH response to TRH (ΔTSH) at 11 PM, lower ΔΔTSH values (differences between 11PM-ΔTSH and 8AM-ΔTSH) (p < 0.03 and p < 0.00001, respectively), and lower free thyroxine (FT4) levels (p < 0.00001); 2) patients with a past suicide attempt (n = 52) showed no major alteration of the HPT axis activity; 3) patients without a suicide attempt history (n = 107) showed both lower 8 AM-ΔTSH and 11-PM ΔTSH (p < 0.04 and p < 0.000001), and lower ΔΔTSH values (p < 0.000001), but no alteration of circulating thyroid hormone levels.

Conclusions:

Our results suggest that in patients without a suicide attempt history increased hypothalamic TRH stimulation (as evidenced by reduced TSH responses to TRH) might be a compensatory mechanism. in patients with a suicide history this compensatory mechanism is not effective. in patients with a recent suicide attempt the evening TSH blunting, associated with reduced FT4 levels, might be indicative of a decreased central TRH activity leading to a reduction in the TSH resynthesis in the thyrotrophs during the day after the morning challenge.