Hypothalamic–pituitary–adrenal axis the midbrain that mediate the general adaptation syndrome (GAS). While steroid hormones are produced mainly in vertebrates, the physiological role of the HPA axis and corticosteroids in stress response is so fundamental that analogous systems can be found in invertebrates and monocellular organisms as well. The HPA axis, HPG axis, HPT axis, and the hypothalamic–neurohypophyseal system are the four major neuroendocrine systems through which the hypothalamus and pituitary direct neuroendocrine function. The key elements of the HPA axis are: CRH and vasopressin are released from neurosecretory nerve terminals at the median eminence. CRH is transported to the anterior pituitary through
Pituitary apoplexy symptoms such as fatigue, weight gain, and cold intolerance. 75% develop a deficiency to gonadotropins (LH and FSH), which control the reproductive hormone glands. This leads to a disrupted menstrual cycle, infertility, and decreased libido. Almost all cases of pituitary apoplexy arise from a pituitary adenoma, a benign tumor of the pituitary gland. In 80%, the patient has been previously unaware of this (although some will retrospectively report associated symptoms). It was previously thought that particular types of pituitary tumors were more prone to apoplexy than others, but this has not been confirmed. In absolute terms, only a very small