In addition, depression leads to neuroendocrine disorders by activating the hypothalamic–pituitary–adrenal (HPA) axis and promoting the secretion of corticotropin-releasing hormone, which in turn promotes the secretion of adrenocorticotropic hormone, resulting in increased cortisol levels, abnormal cortisol rhythms, and fluctuating blood glucose (31). This evidence concerns the gene POMC and major depressive disorder.