Q: What is the pituitary gland?
A: The pituitary gland is a small gland located behind the nasal sinuses and above the roof of the mouth at the base of the skull. It is connected to the hypothalamus, a part of the brain. Together, the two control the production of many of the important hormones in the body. The pituitary gland sits in a tight bony space and has little room to grow or expand when swollen or if there is a tumor.
The pituitary gland regulates the activity of most of the glands in the body, including the adrenal and thyroid glands and sexual hormone production (by regulating ovarian function in women and testicular function in men). The pituitary gland is considered to be the main control gland of the neuro-endocrine system.
The pituitary gland has two parts -- the posterior pituitary (or back part) and the anterior pituitary (front part). The posterior pituitary makes the hormones called vasopressin and oxytocin.
Vasopressin. This hormone allows the kidneys to retain healthy amounts of water rather than excreting it in urine. It can increase blood pressure. It is also called ADH (anti-diuretic hormone).
Oxytocin. This female hormone helps the uterus contract during childbirth and helps the breasts release milk when a woman is nursing.
The anterior pituitary makes several kinds of hormones that, in turn, control other glands throughout the body.
Somatotropin. This is also known as the growth hormone. It helps a child's body grow, especially at puberty. It also helps the liver make insulin-like growth factor (IGF-1). IGF-1 causes bones and other tissues to grow.
Thyroid-stimulating hormone. This hormone (known as TSH and thyrotropin) helps the thyroid gland to grow and to make and release the thyroid hormone.
Adrenocorticotropic hormone (ACTH). This hormone stimulates the adrenal gland so that it can make certain steroid hormones.
Luteinizing hormone (LH). This hormone regulates ovulation and menstruation in women and controls testosterone and the production of sperm in men.
Follicle-stimulating hormone (FSH). This hormone has functions similar to those of LH.
Prolactin. This hormone helps make milk in the female breast. Its function in men is not clear.
Q: What are pituitary tumors?
A: A pituitary tumor is a tumor that begins in the pituitary gland. Most pituitary tumors are not cancer. In fact, cancerous pituitary tumors are so rare that state and national cancer agencies keep no record of how many people get them each year. Benign (non-cancerous) pituitary tumors are also rare. About 7,000 people get them each year.
Q: What are adenomas?
A: There are different kinds of pituitary tumors. However, nearly all of these tumors are adenomas (non-cancerous tumors in the gland). Adenomas usually do not spread out of the pituitary gland. Still, they can greatly affect a person's health by pushing on other parts of the brain and by secreting excess amounts of hormones. Adenomas of the pituitary are classified in two ways:
Size. Microadenomas are tumors that are smaller than one centimeter, or about half an inch. Macroadenomas are tumors that are bigger than one centimeter. Microadenomas and macroadenomas can either make hormones (functional adenomas) or not make hormones (non-functional or null adenomas).
Hormones. Tumors are also grouped according to the type of hormone they produce. The types are named after the types of hormones the pituitary makes and include prolactin-producing adenomas, somatotropin-secreting adenomas, corticotropin-secreting adenomas, gonadotropin-secreting adenomas, thyrotropin-secreting adenomas, null cell adenomas (which do not produce any hormones), and adenomas of the mixed cell type.
Q: What are the risk factors for pituitary tumors?
A: Certain factors can make one person more likely to get a pituitary tumor than another person. These are called risk factors. In some cancers, doctors have identified risk factors that can be avoided, such as smoking or sun exposure. Doctors are not sure what exactly causes pituitary tumors and only one risk factor has been identified. Most people who get a pituitary tumor have no known risk factors.