Many studies have shown that enhanced activity of the hypothalamic–pituitary–adrenal (HPA) axis in depression can be evoked by a reduction in the expression of glucocorticoid receptors (GRs) in the hippocampus or frontal cortex and, as a consequence, a weakening of the inhibitory feedback mechanism [4,48,49]. The gene discussed is NR3C1; the disease is depressive disorder.