What is the physiology of the pituitary gland relative to hypopituitarism (panhypopituitarism)?

Updated: Jun 09, 2020
  • Author: Bernard Corenblum, MD, FRCPC; Chief Editor: Romesh Khardori, MD, PhD, FACP  more...
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Answer

The pituitary gland has 2 parts: the anterior pituitary (adenohypophysis) and the posterior pituitary (neurohypophysis). The anterior pituitary receives signals from the hypothalamus that either stimulate or inhibit secretion of pituitary hormones. These hormones are secreted directly into the systemic circulation, where they act on specific organs.

The actions of the pituitary gland can be modulated at many stages. The pituitary hormones, or target organ hormones, can influence the hypothalamus and the pituitary to decrease or increase pituitary hormone secretion through long and short feedback loops. Hormones secreted by the anterior pituitary include the following:

  • Thyrotropin, or thyroid-stimulating hormone (TSH)

  • Gonadotropins, or follicle-stimulating hormone (FSH) and luteinizing hormone (LH)

  • Somatotropin or growth hormone (GH)

  • Corticotropin, or adrenocorticotropic hormone (ACTH)

  • Prolactin

The posterior pituitary does not produce its own hormones. The hypothalamus produces 2 hormones, vasopressin (VP) and oxytocin (OXT), that are secreted from the nerve axons into the capillary beds that supply the posterior pituitary, where they are stored in cells and ultimately released into the circulation.

Vasopressin, also called antidiuretic hormone (ADH), primarily acts on the V2 receptors of the distal tubules of the kidney to reabsorb water, which increases total body water and urine osmolality and decreases urine volume. Vasopressin, at high levels, also acts as a pressor on the V1 receptors of vascular smooth muscle. Oxytocin induces labor in pregnant women, causing contraction of uterine smooth muscle; the hormone also initiates the mechanics of breastfeeding.


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