Pituitary gland

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Integrates hormonal signals controlling adrenal, thyroid, reproductive, growth and metabolic processes.

Secretes trophic hormones in response to hypothalamic, pituitary and peripheral hormonal and growth factor signals.

1 cm greatest diameter and weighs about 0.5 gm.

The pituitary gland is located in a skull recess in the base of the brain, known as the sella turcica.

It is attached to the hypothalamus, a part of the brain, by a stalk that also contains the blood vessels that supply the gland. 

The pituitary gland has 2 parts: the anterior pituitary, also known as the adenohypophysis and the posterior pituitary, known as the neurohypophysis.

The anterior pituitary receives signals from the hypothalamus that either stimulates or inhibits the 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 modified by decreasing or increasing pituitary hormone secretion through long and short feedback loops.

The posterior pituitary does not produce its own hormones.

The hypothalamus produces 2 hormones, vasopressin (VP) and oxytocin (OXT).

These hormones 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 general circulation.

Vasopressin, also called antidiuretic hormone (ADH), primarily acts on the V2 receptors of the distal tubules of the kidney to reabsorb water.

Vasopressin which increases total body water and urine osmolality and decreases urine volume.

Vasopressin can act as a pressor on the V1 receptors of vascular smooth muscle at high dose.

Oxytocin induces labor in pregnant women, by causing contraction of uterine smooth muscl.

Oxytocin also initiates the mechanics of breastfeeding.

Enlarges during pregnancy.

Pituitary mass lesions include: neoplasms, cysts, hyperplasia, inflammatory lesions, infectious lesions, infiltrative lesions and vascular abnormalities.

Benign adenomas are the most common abnormalities within the pituitary sella.

The pituitary may be involved by a Rathke’s cleft cyst, craniopharyngiomas, meningiomas, germinomas, sarcoidosis, histiocytosis, or metastatic lesions.

Craniopharyngiomas of the pituitary usually arise in the suprasellar region and can extend down to the sella

Located at the base of the brain and lies within the sella turcica.

In close proximity to the optic chiasm, and cavernous sinuses.

Attached to the hypothalamus by the pituitary stalk emanating from the sella through the dura mater.

Along with the hypothalamus it plays a critical role in the regulation of most of the other endocrine glands.

Composed of an anterior lobe and a posterior lobe.

The intermediate lobe is rudimentary in humans.

The intermediate lobe is formed in the embryo from the dorsal half of Rathke’s pouch.

the intermediate lobe is closely associated with the posterior lobe in the adult, and is separated from the anterior lobe by the remains of the cavity of Rathke’s pouch, the residual cleft.

The anterior lobe or the adenohypophysis makes up about 80% of the gland.

The anterior pituitary has a vascular connection with the brain-the portal hypophysial vessels.

The posterior pituitary is largely made up of axon endings on blood vessels from the supraoptic and paraventricular nuclei of the hypothalamus.

Has a portal vascular system for the transport of hypothalamic releasing hormones to the anterior pituitary.

The hypothalamus has neurons with terminals in the median eminence where the hormones are released into the portal system traversing into the pituitary stalk and enter the pituitary gland.

Production of most pituitary hormones is controlled by positive active releasing factors from the hypothalamus.

Prolactin’s primary hypothalamic control is inhibitory through the action of dopamine.

Prolactin acts on the breast.

Growth hormone receives stimulatory and inhibitory effects via the hypothalamus.

Five cell types in the anterior pituitary gland: somatotrophs are acidophilic cells that produce growth hormone, lactotrophs are acidophilic cells that produce prolactin, corticotrophs are basophilic cells that produce adrenocorticotrophic hormone, pro-opiomelanocortin, melanocyte stimulating hormone and lipotropin, thyrotrophs which are basophilic cells that produce thyroid stimulating hormone and gonadotrophs which are basophilic cells that produce follicle stimulating hormone and luteinizing hormone.

Six hormones are secreted by the anterior pituitary with ACTH, Prolactin, and growth hormones which are simple polypeptides or proteins, and TSH, LH, and FSH are glycoprotein.

The anterior pituitary Beta-lipopropin, has an unknown function.

The posterior pituitary, or the neurohypophysis, consists of glial cells and axonal processes extending from supraoptic and paraventricular nuclei via the pituitary stalk.

The posterior pituitary neurons produce antidiuretic hormone (ADH, vasopressin) and oxytocin.

Posterior pituitary hormone oxytocin stimulates contraction of the smooth muscle of the pregnant uterus and the cells of the lactating ducts of the mammary gland.

The anterior pituitary has vascular connection with the portal hypopophysial vessels.

The posterior pituitary is made up of endings on blood vessels of axons from the supraoptic and paraventricular nuclei of the hypothalamus.

ADH, a nonapeptide hormone, synthesized mainly in the supraoptic nucleus.

Has two circulations, one composed of arterial and venous vasculature and a portal venous system that links the hypothalamus to the anterior lobe of the pituitary.

Clinical disease can produce mass effect such as radiographic abnormalities of the sella turcica with expansion, bone erosion, and disruption of the diaphragm sell.