Pituitary tumors are tumors found in the pituitary gland, a small organ about the size of a pea in the center of the brain just above the back of the nose. The pituitary gland produces hormones that affect growth and functions of other glands in the body. Pituitary tumors may be grouped as follows:
- Benign adenomas, which are non-cancerous. These grow very slowly and do not spread from the pituitary gland to other parts of the body.
- Invasive adenomas, which spread to the outer covering of the brain, bones of the skull or the sinus cavity below the pituitary gland.
- Carcinomas, which are malignant (cancer). These are pituitary tumors that have spread far from the pituitary gland in the central nervous system (brain and spinal cord) or outside of the central nervous system.
These pituitary tumors may be either functioning or nonfunctioning. Tumors that make one or more of the pituitary hormones are called functioning tumors, while those that do not make hormones are called nonfunctioning tumors. Each type of functioning tumor causes different symptoms, depending on the type of hormone that is being made by the tumor. Symptoms may also be caused if the tumor grows large and presses on nearby parts of the brain.
Each hormone produced by the pituitary stimulates a certain target gland in the body. These include the adrenal glands, thyroid, breasts, ovaries and uterus, testes and kidneys. One exception is growth hormone, which stimulates all cells of the body.
By sensing the level of hormones that the target glands themselves are producing, the hypothalamus (another gland in the brain) and the pituitary can determine whether these target glands need additional hormonal stimulation, and how much hormone is needed.
This supply-and-demand relationship is a finely tuned system. Any changes in the complex balance of hormones, glands, and stimulation or inhibition responses can create undesirable neurological and endocrinological symptoms.
Fortunately, several strategies can be used to restore endocrine balance, including medication, surgery and/or irradiation.
Many different medical conditions can be caused by pituitary problems. Some of the most common disorders include:
A prolactinoma is the most common type of pituitary tumor (adenoma). These benign (non-cancerous) tumors secrete excessive amounts of prolactin, the hormone responsible for milk production.
Caused by excess secretion of growth hormone – primarily due to benign pituitary tumors called pituitary adenomas – acromegaly is associated with abnormal growth of the limbs. Too much growth hormone before puberty causes increased linear growth (gigantism), while too much hormone after puberty causes periosteal bone growth (bone thickening), increased organ size and glucose intolerance.
Craniopharyngiomas are slow-growing, benign (nonmalignant) tumors at the base of the skull and account for up to 4 percent of primary brain tumors. Although not cancerous, they can cause many serious health problems and complications as they grow and involve other structures in the brain. They can be composed of both solid masses and cysts, and tend to adhere to structures near the pituitary gland and pituitary stalk, including the optic nerves, optic chiasm and intracranial arteries.
- Cushing’s syndrome
Cushing's syndrome, also called hypercortisolism or hyperadrenocorticism, is a rare endocrine disorder characterized by excessive cortisol levels in the blood. These high levels are due to excess adrenocorticotropic hormone secretion. Most commonly the excess comes from a tumor of the pituitary gland or the adrenal glands.
- FSH and LH tumors
These rare tumors of the pituitary secrete excess amounts of the gonadotropin hormones, follicle-stimulating hormone (FSH) and luteinizing hormone (LH).