INFLUENCE OF THYROID-HORMONES ON MORNING AND EVENING TSH RESPONSE TO TRH IN MAJOR DEPRESSION

The serum levels of thyroid hormones and thyrotropin (TSH) were evalua ted before and after 8 PM and 11 PM thyrotropin-releasing hormone (TRH ) challenges, on the same day, in 41 drug-free DSM-III-R euthyroid maj or depressed inpatients and 16 hospitalized controls. Depressed patien ts exhibited elevated circulating concentrations of thyroid hormones, which were associated with and may have contributed to the blunted TSH response to TRH. This was confirmed by: (a) higher basal levels (albe it not always statistically significant) of free triiodothyronine (FT3 B) and free thyroxine (FT4B) at 8 AM and 11 PM in the depressed patien t population compared with the controls; (b) lower basal levels of TSH in the depressed subjects (even though this,vas only statistically si gnificant at the 11 PM sampling) compared with the controls; (c) blunt ed TSH response to TRH (Delta TSH) in the depressed group (although th is was only statistically significant at II PM) and blunted Delta Delt a TSH values (differences between 11 PM-Delta TSH and 8 AM-Delta TSH).