The pituitary gland is a tiny organ, the size of a pea, found at the base of the brain. As the master gland of the body, it produces and secretes many hormones that travel throughout the body, directing certain processes stimulating other glands to produce different types of hormones. The pituitary gland controls biochemical processes important to our well-being.

The pituitary gland makes these types of hormones:

1. Prolactin – Prolactin stimulates milk production from the breasts after childbirth to enable nursing. It also affects sex hormone levels from ovaries in women and from testes in men.

2. Growth hormone (GH) – GH stimulates growth in childhood and is important for maintaining a healthy body composition and well-being in adults. In adults it is important for maintaining muscle mass as well as bone mass. It also affects fat distribution in the body.

3. Adrenocorticotropin (ACTH) – ACTH stimulates the production of cortisol by the adrenal glands. Cortisol, a so-called “stress hormone” is vital to our survival. It helps to maintain blood pressure and blood glucose levels.

4. Thyroid-stimulating hormone (TSH) – TSH stimulates the thyroid gland, which regulates the body’s metabolism, energy, growth, and nervous system activity. This hormone is also vital to our survival.

5. Antidiuretic hormone (ADH) – ADH, also called vasopressin, regulates water balance. If this hormone is not released properly, it can lead to too little hormone (called diabetes insipidus), or too much hormone (called syndrome of inappropriate ADH). Both of these conditions affect the kidneys. Diabetes insipidus is different from the more well-known diabetes mellitus (including type 1 and type 2 diabetes), which affects the levels of glucose in our bodies.

6. Luteinizing hormone (LH) – LH regulates testosterone in men and estrogen in women.

7. Follicle-stimulating hormone (FSH) – FSH promotes sperm production in men and stimulates the ovaries to enable ovulation in women. Luteinizing hormone and follicle-stimulating hormone work together to cause normal function of the ovaries and testes.

Pituitary Tumors

The most frequent cause of pituitary disorders is pituitary gland tumors. The pituitary gland is made of several cell types. Sometimes these cells grow too much or produce small growths.

These growths are called pituitary tumors, and they are fairly common in adults. These are not brain tumors and are not a form of cancer. In fact, cancerous tumors of this sort are extremely rare. Pituitary tumors, however, can interfere with the normal formation and release of hormones.

Two types of tumors exist – secretory and non-secretory. Secretory tumors produce too much of a hormone, creating an imbalance of proper hormones in the body. Non-secretory tumors cause problems because of their large size or because they interfere with normal function of the pituitary gland.

The problems caused by pituitary tumors fall into three general categories:

1. Hypersecretion – Too much of any hormone secreted into the body is usually caused by a secretory pituitary gland tumor. Many secretory tumors make too much prolactin, the hormone that triggers milk production in new mothers. Other tumors may affect the adrenal glands, making too much of the hormones that stimulate them and causing a hormone imbalance. Tumors also can make excess growth hormone or too much of the hormone that stimulates the thyroid gland leading to overproduction of thyroid hormones.

2. Hyposecretion – Too little of any hormone secreted into the body is usually caused by a non-secretory pituitary gland tumor, which interferes with the ability of the normal pituitary gland to create hormones. It can, however, also be caused by a large secretory tumor. Hyposecretion can also happen with surgery or the radiation of a pituitary gland tumor.

3. Tumor mass effects – As a pituitary gland tumor grows and presses against the normal pituitary gland or other areas in the brain, it may cause headaches, vision problems, or other health effects related to hyposecretion. Tumor mass effects can be seen in any type of pituitary tumor that grows large enough. Injuries, certain medications, and other conditions can also affect the pituitary gland. Loss of normal pituitary function also has been reported after major head trauma.

© 2012 The Hormone Foundation. All rights reserved.