Glossary of Pituitary Terminology
ACTH is important in controlling the adrenal gland’s secretion of cortisol and androgens (male hormones). Too much ACTH causes a disease called Cushing’s disease and too little ACTH causes adrenal insufficiency. Symptoms of adrenal insufficiency include weight loss, decrease in appetite, abdominal pain, and muscle aches. Please see the additional patient education material on this Web site for further information.
ADH is a critical hormone that regulates water balance in the body by controlling how much water the kidneys release into the urine. Too much ADH secretion by the pituitary causes the syndrome of inappropriate antidiuretic hormone (SIADH), in which the salt levels in the body can drop dangerously low due to holding on to too much water. Treatments may include fluid restriction and salt supplementation. Too little ADH results in diabetes insipidus (DI), in which the body constantly produces a clear high volume of urine accompanied by extreme thirst. The treatment is fluids and a medicine called DDAVP. Additional information regarding diabetes insipidus may be found in patient education material on this Web site.
A rare disorder called acromegaly occurs when a person’s pituitary gland secretes too much growth hormone, usually from a pituitary tumor. Symptoms of this disorder may include broadening of the lips and nose, irregular menstrual periods, excessive sweating and increasing ring and shoe size. Surgery is generally indicated for the treatment of acromegaly. There are several medications that are frequently used in addition to surgery to control acromegaly, and, occasionally, radiation therapy is required as well.
Too much ACTH secretion is rare and may be from a pituitary tumor; this is called Cushing’s disease. Symptoms of too much ACTH include weight gain, a round and red face, increased acne, purple stretch marks, hair growth and muscle weakness. Special testing is necessary to make the diagnosis. Surgery is generally indicated for the treatment of Cushing’s disease. Medications are also available to lower cortisol production, and radiation therapy is sometimes required as well.
The gonadotropins are responsible for the initiation and maintenance of sexual characteristics and fertility (ability to have children). LH and FSH act on the gonads (ovaries and testes) to cause production of estrogen and testosterone and ultimately make eggs and sperm. Too little secretion of LH and FSH can cause infertility and hypogonadism, manifesting primarily as erectile dysfunction in men and irregular or absent menstrual periods in women as well as low sex drive in both. Treatment includes various forms of testosterone or estrogen replacement. Fertility can be possible with the assistance of injectable forms of gonadotropins.
As its name implies, growth hormone is important for childhood growth. In adults, it is also important in order to maintain bone mass and normal body composition. Symptoms of growth hormone deficiency include fatigue, an increase in fat around the abdomen, decreased ability to exercise and poor sense of well-being. Treatment includes subcutaneous injections of growth hormone.
Oxytocin is a hormone that is important for uterine contractions during childbirth and for release of milk during breastfeeding. It is, therefore, frequently used in the induction of labor.
The pituitary is a pea-sized gland located at the base of the brain in the middle of the head and right below the optic nerves. It serves as the “master gland” that regulates the secretion of the majority of hormones in the body from all of the other glands, such as the thyroid and adrenal glands, as well as the ovary and testicles. The pituitary gland is divided into the anterior and posterior lobes, both of which secrete different hormones that have unique functions in the body. The anterior pituitary secretes prolactin, growth hormone and the gonadotropins, which include luteinizing hormone (LH) and follicle stimulating hormone (FSH), adrenocorticotrophic hormone (ACTH) and thyroid stimulating hormone (TSH). The posterior pituitary makes antidiuretic hormone (ADH) and oxytocin. The secretion of the hormones from the pituitary gland itself is also controlled by hormones coming from part of the brain directly above the pituitary called the hypothalamus. The hypothalamus and the pituitary gland are connected by the pituitary stalk.
Pituitary tumors result from a single cell losing the ability to control its growth. These tumors are almost always benign or non-cancerous. Very rarely can a pituitary tumor become malignant or cancerous. A tumor that is less than 1 cm in size is called a microadenoma, and a tumor that is larger than 1 cm is a macroadenoma.
Microadenomas usually do not cause symptoms related to their size, but macroadenomas can cause headaches as well as visual loss secondary to compression of the optic nerves. In addition, the normal pituitary tissue can be compressed by a macroadenoma, so deficiencies of anterior pituitary hormones can be identified on blood tests and based on symptoms. Pituitary tumors are also categorized according to their ability to make hormones and cause symptoms.
The functional tumors include those that secrete prolactin (prolactinomas), ACTH (Cushing’s disease), growth hormone (acromegaly) and TSH. Tumors that do not secrete functional hormones are called non-functioning pituitary tumors. The most common tumors in adults are prolactinomas followed by non-functioning tumors, ACTH-secreting tumors, GH-secreting tumors and TSH-secreting tumors. In children, the most common tumor is also a prolactin-secreting tumor followed by ACTH-secreting tumors, GH-secreting tumors, non-functioning tumors and TSH-secreting tumors.
Prolactin is a hormone that is important for the production of breast milk.
A pituitary tumor that secretes prolactin is called a prolactinoma. In women, too much prolactin is associated with milk production outside of pregnancy and irregular menstrual periods or a lack of periods altogether. In men, excess prolactin levels cause low testosterone levels, which will typically manifest as low sex drive. Medical treatment with a pill is available for a prolactinoma. Women with too little prolactin production will be unable to make breast milk but otherwise there are no obvious symptoms of prolactin deficiency.
Thyroid stimulating hormone (TSH) directs the thyroid gland to produce thyroid hormones, which are important in regulating the body’s metabolism. Rarely, a pituitary tumor can secrete too much TSH. This would cause hyperthyroidism, as manifested by increased sweating, intolerance to heat, tremors, fast heart rate, heart palpitations, anxiety and/or weight loss. Treatment includes medications and surgery. Too little TSH results in hypothyroidism, a condition in which a person would have intolerance to cold, fatigue, dry skin, constipation, a slow heart rate and/or weight gain due to water retention. Treatment includes taking daily thyroid hormone.