Pituitary Gland

The pituitary gland, or hypophysis, is about the size of a pea and sits in the small, bony cavity (sella turcica) at the base of the brain. The pituitary gland is divided into two sections: the anterior lobe (adenohypophysis) and the posterior lobe (neurohypophysis). The posterior pituitary is, in effect, a projection of the hypothalamus. It does not produce its own hormones, but only stores and releases the hormones created by the hypothalamus, whereas the anterior pituitary produces and secretes its own hormones.

Posterior Pituitary

ADH and oxytocin are produced in neuronal cell bodies of the supraoptic and paraventricular nuclei in the hypothalamus. They are then transported along the axons of the hypothalamo-hypophyseal tract to the posterior pituitary, where they are stored. Later they are released into the capillary plexus of the infundibular process which passes the hormones to the posterior hypophyseal portal veins for distribution to target cells in other tissues. Remember, no hormones are actually produced in the posterior pituitary, they are only stored!!

Note: The posterior pituitary is lighter in color than the anterior pituitary because it is made of myelinated neuronal tissue (white matter). This is apparent upon both gross and microscopic examination.


Hormones Target Organ Principle Action
ADH (Antidiuretic hormone) Kidneys and sweat glands

Conserves body water by decreasing urine volume; decreases water loss through perspiration; raises blood pressure by constricting arterioles.

Oxytocin Uterus and mammary glands Stimulates contraction of uterus during child birth; Stimulates contraction of mammary glands to cause milk ejection.

Anterior Pituitary

Although the hypothalamus does not produce the hormones of the anterior pituitary as in the posterior pituitary, it plays an important role in their production. Releasing hormones synthesized by hypothalamic neurons travel down axons and diffuse into the primary plexus of the hypophyseal portal system. They are then carried by the hypophyseal portal veins to the secondary plexus for distribution to target cells within the anterior pituitary.

The hormones produced by the anterior pituitary are described in the table below.

Note: Make sure you are clear on the difference between releasing hormones and hormones produced by the anterior pituitary. Releasing hormones are produced in the hypothalamus and stimulate production of anterior pituitary hormones.

Hormones Target Tissue Principle Action
ACTH (Adrenocorticotropic hormone) Adrenal cortex

Stimulates secretion of glucocorticoids.

TSH (Thyroid stimulating hormone) Thyroid gland Stimulates secretion of thyroid hormones.
hGH (Human growth hormone) Liver Promotes protein synthesis and growth; lipolysis and increased blood glucose.
FSH (Follicle stimulating hormone) Gonads Promotes gamete production and estrogen production in females.
PRL (Prolactin) Mammary Glands Promotes milk production in lactating females.
LH (Luteinizing hormone) Gonads Stimulates sex hormone secretion; ovulation and corpus luteum formation in females; testosterone secretion in males.
MSH (Melanocyte-stimulating hormone) Skin Contributes to darkening of the skin.

Histology of Pituitary

Can you identify the adenohypophysis and the neurohypophysis?

Test your knowledge and take a quiz on the pituitary gland

Thyroid Follicle Neuronal Cell Bodies Axons to Primary Plexus Primary Plexus Hypophyseal Portal Veins Secondary Plexus Anterior Pituitary Posterior Pituitary Infundibulum Paraventricular Nuclei Optic Chiasma Anterior Pituitary Posterior Pituitary Hypothalamo-hypophyseal Tract Infundibulum Supraoptic Nuclei Hypothalamus Posterior Pituitary Anterior Pituitary Hypothalamus