The Pituitary Gland
The pituitary controls the function of most other endocrine (hormone) glands and is therefore sometimes called “the master gland.” It secretes hormones (chemicals that carry messages from one cell to another through the bloodstream) from both the front part (anterior) and the back part (posterior) of the gland. In turn, the pituitary is controlled in large part by the hypothalamus, a region of the brain that lies just above the pituitary. By detecting the levels of hormones produced by glands under the pituitary's control (target glands), the hypothalamus or the pituitary can determine how much stimulation the target glands throughout the body need. The pituitary is a pea-sized gland that is located within a bony structure called the sella turcica at the base of the brain, just behind the bridge of the nose. The sella turcica protects the pituitary gland but allows very little room for expansion of the gland.
How does the pituitary gland work?
As mentioned above, the pituitary has two distinct parts, the anterior lobe and posterior lobe. The anterior lobe of the pituitary produces and releases six main hormones. Growth hormone regulates growth and physical development and has important effects on body shape by stimulating muscle formation and reducing fat tissue. Thyroid-stimulating hormone stimulates the thyroid gland to produce thyroid hormones. Adrenocorticotropic hormone (ACTH) stimulates the adrenal glands to produce cortisol and other hormones. Follicle-stimulating hormone and luteinizing hormone signal the testes to produce sperm, the ovaries to produce eggs, and both sex organs to produce hormones (testosterone and estrogen). Prolactin stimulates the mammary glands of the breasts to produce milk.
The posterior lobe of the pituitary produces only two hormones. Vasopressin (also called antidiuretic hormone) regulates the amount of water excreted by the kidneys and is therefore important in helping the body regulate water. The last hormone is called oxytocin, which causes the uterus to contract during childbirth and immediately after delivery to prevent excessive bleeding. Oxytocin also stimulates contractions of the milk ducts in the breast, which move milk to the nipple (the let-down) in lactating women.
What are the most common pituitary gland disorders?
Pituitary tumors Tumors are the most common cause of pituitary dysfunction and are usually noncancerous. In fact, cancerous tumors of this sort are extremely rare. However, they often interfere with the release of hormones. They can also press against other areas of the brain, leading to vision problems or headaches. These tumors are fairly common in adults. Some pituitary tumors can exist for years without causing any symptoms and some will never produce symptoms at all.
Hypopituitarism This condition causes the pituitary gland to produce very little or none of one or more of its hormones. This can affect things like growth or reproductive system function. Signs and symptoms of hypopituitarism vary, depending on which pituitary hormones are deficient and how severe the deficiency is.
Diabetes insipidus This can be caused by a problem with the release of vasopressin. It’s usually due to a head injury, surgery, or a tumor. As a result, people with condition pass large amounts of heavily diluted urine. They may also feel like they need to drink a lot of water or other fluids.
Acromegaly In this condition, the pituitary gland produces too much growth hormone. This can lead to excessive growth, especially of the hands and feet. Acromegaly is often associated with pituitary tumors.
Cushing’s disease. In this disease, the pituitary gland releases too much adrenocorticotropic hormone. This can lead to easy bruising, high blood pressure, weakness, and weight gain. It’s often caused by a tumor near or in the pituitary gland.
Hyperprolactinemia A tumor on the pituitary known as a prolactinoma may cause the gland to secrete too much prolactin. High levels of prolactin can disrupt normal reproductive functions in men and women by interfering with hormones produced by the testes and ovaries. A prolactinoma can cause women who are not pregnant or nursing to experience tenderness of the breasts and start to produce breast milk (galactorrhea). Also, menstrual periods may become irregular or might stop altogether.
Hyperthyroidism If the pituitary adenoma causes overproduction of thyroid stimulating hormone (TSH), the thyroid gland will become hyperactive. Symptoms may include nervousness, rapid or irregular heartbeat, weight loss, fatigue, or muscular weakness.
Traumatic brain injury This involves a sudden blow to the brain. Depending on the injury, it can sometimes damage the pituitary gland and cause problems with memory, communication, or behavior.
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