Pars intermedia

Pars intermedia is a part of the pituitary gland that is situated between the anterior pituitary and the posterior pituitary. It is also known as the intermediate lobe of the pituitary gland. The pars intermedia is responsible for the production of melanocyte-stimulating hormone (MSH), which plays a crucial role in the pigmentation of the skin and hair in mammals.

Structure

The pars intermedia is a thin layer of tissue that separates the anterior and posterior lobes of the pituitary gland. It is composed of melanotrophs, which are cells that produce and secrete MSH. The pars intermedia is more prominent in animals than in humans, where it is often rudimentary or absent.

Function

The primary function of the pars intermedia is the production and secretion of MSH. This hormone stimulates the production and release of melanin, the pigment responsible for the color of the skin, hair, and eyes in mammals. MSH also has effects on appetite and sexual behavior, although these functions are less well understood.

Clinical significance

Abnormalities in the pars intermedia can lead to a variety of medical conditions. For example, Cushing's disease in dogs is often caused by a tumor in the pars intermedia. This results in an overproduction of MSH, leading to symptoms such as darkening of the skin and hair loss. In humans, a rare condition known as Nelson's syndrome can occur following the surgical removal of the adrenal glands, leading to an overproduction of MSH and darkening of the skin.

See also

• Pituitary gland
• Anterior pituitary
• Posterior pituitary
• Melanocyte-stimulating hormone
• Cushing's disease
• Nelson's syndrome

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