THE PITUITARY

THE PITUITARY

The Pituitary:

Background:The anterior part of the 1x1x1 cm pituitary gland is made up of six different types of secretory cells. They secrete into the blood stream six different hormones that in turn control the secretion of hormones from corresponding peripheral target glands in the body. Hormones from these target glands in the body have feedback effects on the pituitary gland regulating the corresponding pituitary hormone secretion. Many hormone functions in the body are kept in stable balance by being locked into this feed back system. In addition, the function of the pituitary gland is also regulated by secretion of specific hormones produced in the hypothalamic part of the brain and carried to the pituitary through local blood vessels. Pituitary function is robust and disease in the pituitary is relatively rare.

ACTHcontrols the secretion of hormones from the adrenal glands.
TSHcontrols the secretion of T4 from the thyroid gland and the conversion of T4 to T3 in the body.
LHcontrols ovulation and the secretion of progesterone from the ovaries and secretion of testosterone from the testes.
FSHcontrols the secretion of estrogen from the ovaries and production of sperm in the testes.
HGHcontrols the body growth during childhood.
Prolactincontrols the secretion of milk from the breasts.

Symptoms: The pituitary may even without surgical intervention secrete too little of one of the six hormones individually or of all six hormones simultaneously. This will cause too low secretion of hormones from the corresponding target glands in the body. Each of the six cell types in the pituitary may multiply separately and secrete too much hormone and thereby stimulate increased secretion of hormones from the target gland. Increased or decreased hormone secretion from the target glands in the body may therefore be secondary to abnormal pituitary function. It may also be a primary malfunction of the target gland. Increased growth of any one of the six cell types will cause volume expansion of the pituitary and compression of the remaining five cell types. Expansion of the volume of the pituitary gland will cause characteristic head ache and may impinge on the nearby optic nerves resulting in visual field defects.

Diagnosis: Of pituitary disease is initially made by findings of abnormal concentrations of pituitary hormones or target gland hormones in blood. Increased cell growth of the pituitary is visualized by MRI scans. Dopamine flow from the hypothalamus to the pituitary keeps the prolactin secretion suppressed. Volume expansion of the pituitary will compress the blood vessels carrying dopamine to the pituitary, thereby releasing prolactin into the blood stream. This moderate increase in the prolactin concentration in blood signals pituitary volume expansion, whereas higher prolactin concentration in blood is a sign of tumor growth of the prolactin producing cells.

Treatment:Decreased hormone production in the pituitary is replaced by the hormone that should have been produced in the target gland had it been stimulated by the pituitary hormone (For instance by T4 medication, if increased TSH stimulation is not sufficient to keep the T4 production normal). Increasing cell growth of the pituitary causing symptoms of volume expansion can in certain cases be treated by oral medication that suppresses the cell growth, or rarely by radiation. However, pituitary cell growth is most often treated by operation via a microscope through the nose, which is not altered by the operation.
FW © 05/ 2018