Neuroendocrine Abnormalities Associated with Untreated First Episode Patients with Major Depressive Disorder and Bipolar Disorder

There are few studies that explore simultaneously the relationship of neuroendocrine hormones of the HPA, HPT and HPG axes with major depressive disorder (MDD) and bipolar disorder (BD). The aim of this study is to examine the relationship of neuroendocrine pathways with affective disorders by comparing the differences in measures of neuroendocrine function between untreated first episode patients with MDD and BD. A cohort of 679 MDD and 83 BD patients was recruited. Thyroid stimulating hormone (TSH), triiodothyronine (T3), free triiodothyronine (FT3), thyroxine (T4), free thyroxin (FT4), cortisol (COR), adrenocorticotropic hormone (ACTH), estradiol (E2) and testosterone (T) were determined by chemiluminesent immunoassay for all patients. COR and ACTH were both significantly higher in the MDD group than those in BD group. The incidences of high secretion of ACTH and COR, and low thyroid hormone secretion were significantly greater in MDD patients than in BD patients. Decreased T secretion was more common in BD than MDD patients. ACTH was significantly positively correlated with HAMD total score and negatively correlated with FT3 in MDD patients. FT3 and FT4 levels were significantly negatively correlated with the somatoform factor score of HAMD in MDD patients. Untreated first episode patients with MDD have a hyperactivity of the HPA axis, lower HPT compared with BD patients. BD patients had reduced testosterone secretion. These findings indicate that ACTH, FT3 and FT4 could be used as markers for severity and symptoms of untreated first episode patients with MDD.