The normal homeostatic regulation of the hypothalamic-pituitary pathways due to stimulatory (+) and inhibitory (−) signals is shown. i.e., for the hypothalamic-pituitary-adrenal pathway, the hypothalamus releases CRH, which stimulates (+) the secretion of ACTH from the pituitary gland. The ACTH then stimulates (+) release of cortisol from the adrenal glands. The cortisol would then send negative feedback signals (−) to both the hypothalamus and pituitary gland to inhibit the any further release of CRH and ACTH respectively. Similar homeostastic regulation occurs with the hypothalamic-pituitary-thyroid and hypothalamic-pituitary-gonadal axes. Abbreviations: ACTH - adrenocorticotroic hormone, CRH - corticotropin-releasing hormone, FSH – follicle-stimulating hormone, LH - luteinizing hormone, TSH - thyroid-stimulating hormone, T3 - triiodothyronine, T4 - thyroxine. Figure was adapted and modified from original (Ishii, 2014).