A FURTHER INVESTIGATION OF BASAL HPT AXIS FUNCTION IN UNIPOLAR DEPRESSION - EFFECTS OF DIAGNOSIS, HOSPITALIZATION, AND DEXAMETHASONE ADMINISTRATION

Hypothalamic-pituitary-thyroid (HPT) axis function was assessed in dep ressed subjects 1 and 8 days after hospital admission, and after the a dministration of 1 mg of dexamethasone. Plasma levels of thyroid stimu lating hormone (TSH), free triiodothyronine (FT3), and free thyroxine (FT4) were measured by ultrasensitive assays in 16 patients with minor depression, 15 patients with simple major depression, and 13 patients with melancholia. The postdexamethasone adrenocorticotropic hormone ( ACTH) (intact 1-39 molecule) and cortisol values were determined. Basa l TSH values were significantly lower in melancholic patients than in patients with minor and simple major depression on the day after admis sion and 1 week later. Basal TSH values determined 1 week after admiss ion were significantly and negatively related to FT4 values and severi ty of depression. There were no significant differences in basal TSH, FT3, and FT4 values obtained on day 1 and day 8 after hospital admissi on. Dexamethasone administration had a significant suppressant effect on basal TSH and FT3 values. Patients who failed to suppress cortisol after the dexamethasone suppression test (DST) exhibited significantly less suppression of basal TSH values than did DST cortisol suppressor s.