Pituitary tumor

Definition

A pituitary tumor is an abnormal growth in the pituitary gland, the part of the brain that regulates the body's balance of hormones.

Alternative Names

Tumor - pituitary

Causes

The pituitary gland is a pea-sized endocrine gland located at the base of the brain. The pituitary regulates and controls the secretion of hormones from other endocrine glands, which in turn regulate many body processes. These hormones include:

• Growth hormone (GH)
• Thyroid-stimulating hormone (TSH)
• Adrenocorticotropic hormone (ACTH)
• Prolactin

About 75% of pituitary tumors secrete hormones. When a tumor produces excessive amounts of one or more hormones, the following conditions may occur:

• Gigantism or acromegaly (excess growth hormone)
• Hypothyroidism (excess thyroid stimulating hormone)
• Cushing syndrome (excess adrenocorticotropic hormone)
• Prolactinoma (excess prolactin)

As the tumor grows, hormone-secreting cells of the pituitary may be damaged, causing hypopituitarism.

The causes of pituitary tumors are unknown, although some are a part of a hereditary disorder called multiple endocrine neoplasia I (MEN I).

There are other types of tumors that can be found in the same area of the head as a pituitary tumor:

• Craniopharyngiomas
• Germinomas
• Cysts
• Metastatic tumors (tumors that have spread from cancer in another part of the body)

About 15% of tumors located within the skull are pituitary tumors. Most pituitary tumors are located in the anterior pituitary lobe and are usually benign (noncancerous).

Pituitary tumors develop in about 20% of people, although many of the tumors do not cause symptoms and the condition is never diagnosed during the person's lifetime.

References

Ezzat S, Asa SL, Couldwell WT, et al. The prevalence of pituitary adenomas. Cancer. 2004 Aug 1;101(3):613-9. Review.