Therefore, plasma or serum BDNF serves as an endocrine molecule and is proposed as a biomarker for various diseases, including hepatic encephalopathy (96), depression (61, 97), Alzheimer's disease (98), mood disorders (99), schizophrenia (100), neuropsychiatric disorders (101), obesity (102), psoriasis (103), cardiometabolic problems (104), and glaucoma (105), among others. The gene discussed is BDNF; the disease is major depressive disorder.