Hypothalamic–pituitary–gonadal axis Hypothalamic–pituitary–gonadal axis The hypothalamic–pituitary–gonadal axis (HPG axis) refers to the hypothalamus, pituitary gland, and gonadal glands as if these individual endocrine glands were a single entity. Because these glands often act in concert, physiologists and endocrinologists find it convenient and descriptive to speak of them as a single system. The HPG axis plays a critical part in the development and regulation of a number of the body's systems, such as the reproductive and immune systems. Fluctuations in this axis cause changes in the hormones produced by each gland and have various local and systemic effects on the body. The axis
Pituitary stalk tract. It has been thought that the pituitary stalk may become compressed due to suprasellar tumors in the pars tuberalis region, and that the resulting compression may cause hyperprolactinemia. This phenomenon has been described as the stalk effect or pituitary stalk compression syndrome. However, at least one article suggests that the increase in prolactin in these cases may instead be caused by the tumor's secretion of preprotachykinin A-derived tachykinins, substance P, and/or neurokinin A. Damage to the pituitary stalk blocks the release of antidiuretic hormone, resulting in polydypsia (abusive water intake) and polyuria (excessive urination). Pituitary stalk The pituitary stalk