What can go wrong?
The most common problem with the pituitary is the development of a tumor. While most are benign, they can produce excessive amounts of a specific pituitary hormone, crowd out the production of other hormones, and compress surrounding tissues. Blood vessels and the optic nerves are in close proximity to the pituitary gland. Pressure from a tumor can cause headaches, visual disturbances, loss of vision, fatigue, weakness, and seizures, as well as a host of signs and symptoms related to decreased hormone production.
Other pituitary disorders can arise from inherited genetic mutations, exist at birth (congenital), be caused by trauma or an impaired blood supply, be caused by surgical or radiation treatment of a previous pituitary disorder, a malignant tumor (rare), or be due to causes that are not yet well understood. Excess or deficient hormones from these disorders can produce a variety of symptoms depending on which hormones and target tissues are affected.
When the hypothalamus is dysfunctional, pituitary hormone production is often affected. Excess or deficient hormone production by the pituitary may also occur if the glands "downstream" from it are dysfunctional. For example, normally the hypothalamus detects thyroid hormone deficiency in the blood and stimulates the pituitary to produce thyroid-stimulating hormone (TSH). TSH in turn stimulates the thyroid gland to produce thyroid hormone. If the thyroid gland is dysfunctional and cannot produce adequate thyroid hormone, then blood thyroid hormone levels will remain below normal even though the hypothalamus and pituitary are promoting production. The result is excessive amounts of TSH and deficient thyroid hormone concentrations.
Examples of Common Pituitary Disorders
- Pituitary tumors: may be hormone-secreting or non-secreting; most are benign; may cause visual disturbances and headaches as they grow and compress surrounding tissues; they often result in excessive amounts of one pituitary hormone and decreases in others.
- Growth hormone deficiency: in children, it causes delayed growth and short stature; in adults, it can lead to muscular weakness, fatigue, decreased bone mass, and obesity.
- Hypopituitarism: causes may include tumors, trauma, decreased pituitary blood supply, infection, sarcoidosis, an autoimmune process, radiation, surgical removal of the pituitary, or a side effect of pituitary surgery; it results in a general decrease in pituitary hormone production.
- Hyperprolactinemia: caused by a pituitary tumor that secretes prolactin or a tumor that prevents the regulation of prolactin production; can cause galactorrhea and amenorrhea and, in men, decreased sex drive and impotence.
- Empty Sella Syndrome: the sella is a hollow area in the bone of the skull that holds the pituitary; a membrane, called the sellae, sits on top of the pituitary and protects it within this socket. If there is an opening in this membrane, spinal fluid may press on the pituitary, flattening it and making it appear as though the sella is empty when viewed with an imaging procedure (i.e, MRI). Sometimes, people can have empty sella syndrome caused by other factors, such as a tumor or radiation therapy.
- Craniopharyngioma: most commonly occurs in children and adolescents but also occurs in adults after 50; while benign, it but may put pressure on the pituitary, causing hypopituitarism, headaches, visual disturbances, and delayed growth.
Examples of Rare Pituitary Disorders
- Acromegaly and Gigantism: excess growth hormone production, usually due to a benign tumor (adenoma); when it occurs in childhood, it causes gigantism associated with excessive bone growth and abnormally tall stature; in adults, it causes acromegaly, with increases in bone thickness, coarsened facial features, enlarged hands and feet, carpal tunnel syndrome, headaches, sweating, sleep apnea, fatigue, and hypertension along with an increased risk of diabetes mellitus and colon cancer.
- Cushing Disease: Cushing syndrome symptoms caused by a pituitary tumor that produces excess ACTH and exposes the adrenal gland to the hormone cortisol; symptoms vary but include: upper body obesity, a rounded face, thin skin, pink streaks on the abdomen, muscular weakness, osteoporosis, high blood sugar, and high blood pressure.
- Diabetes Insipidus: decreased production of ADH by the hypothalamus; an individual's kidneys don't conserve water and concentrate urine and the person becomes thirsty and has frequent, dilute urination.
- Nelson Syndrome: may result when both adrenal glands are removed as part of the treatment for Cushing disease; a pituitary tumor develops that produces ACTH and can cause darkening of the skin due to increased production of melanocyte-stimulating hormone (MSH).
- Multiple Endocrine Neoplasia Type 1 (MEN1): an inherited genetic mutation that increases the risk of developing tumors in the pituitary and in other endocrine glands.
- Kallman Syndrome: an inherited condition caused by deficient release of gonadotropin-releasing hormone (GnRH); it leads to lack of FSH and LH production, causes delayed or absent puberty, and is associated with no sense of smell.
- Pituitary infarction: the most common cause is bleeding due to a noncancerous pituitary tumor; it may cause gland tissue damage and lead to hypopituitarism.
- Sheehan Syndrome: a very rare condition caused by severe bleeding during childbirth that can cause the pituitary gland to lose function; it is a specific kind of pituitary infarction.