Pituitary adenomas are the most common of pituitary gland abnormalities. Technically benign brain neoplasms, they account for up to 20 percent of brain tumors in general.
The pituitary gland sits at the base of the skull and is supported in a structural support called the sella turcica. This structure forces the growth of an adenoma upward toward the superior brain and optic nerve. Its effects can be felt by either destroying adjacent tissue or by causing the excess secretion of hormones from the involved area.
The pituitary gland has different types of specialized cells, each producing different hormones into the bloodstream. As with all endocrine organs, any change in hormone levels triggers a series of events that affect other body organs in a stimulatory or suppressive way. If the tumor cells cause an excess of hormone to be secreted, it is called a functional adenoma. Those that don’t cause hormone to be secreted are called nonfunctional, and have their effects by occupying space and causing gland destruction just by their size and compression of neighboring structures.
Pituitary adenomas are generally characterized by their size, hormone secretion and aggressiveness. Microadenomas are generally small, less than one centimeter in size; macroadenomas are the larger ones.
Since the pituitary gland has so many functions, the hormones each cell secretes cause their effects by the nature of the hormone itself—these are referred to as functional adenomas. Most pituitary tumors are slow growing and benign, but the ones that are atypical are aggressive, sometimes make up the few that are malignant, and are most likely to recur even after surgery to remove them.
Symptoms from pituitary tumors mirror either the hormones that are being overproduced or the ones that are now lacking because the normal cells producing them have been destroyed by the growth.
For instance, in prolactinoma, the tumor causes an overproduction of prolactin, which affects menstrual periods in women and testosterone levels in men. Those related to overproduction of growth hormones cause either gigantism if the tumor occurs before growth has been completed in children, or acromegaly (large bones throughout the skeleton) in adults.
ACTH overproduction causes Cushing’s disease, where too much cortisone is produced and both the healing and structural integrity of the body is affected. TSH secreting tumors cause hyperthyroidism.
On the other end of the spectrum, a nonfunctioning tumor may compress areas that produce hormones, and the body may suffer from a decrease of each, called hypopituitarism. Infertility, hypothyroidism, secondary adrenal insufficiency and growth hormone insufficiency are a few of the problems that may occur.
If a tumor is large and grows out of the sella turcica, it can compress the optic chiasm and cause problems with vision.
The diagnostic approach to a suspected pituitary adenoma depends on the presenting syndrome. For all of the diseases mentioned above, specific blood tests and hormone stimulation testing helps to reveal the source of the problem. When the pituitary gland is implicated, an MRI is the best initial imaging study. CT scans can be used as well, although they are not as accurate, especially around the optic nerve.
For underwriting, most pituitary adenomas are evaluated by which hormone is compromised, how complete the treatment is, and if there are any permanent consequences after surgery.
When a pituitary tumor is completely removed by surgery and all systems are functioning normally, a best-case underwriting scenario is a standard issue. When residual tumor is left behind, observation time is needed to see that it has been completely treated and is not growing.
Medication can treat certain pituitary tumors, such as prolactinomas, about as well as surgery. Panhypopituitarism (a loss of all hormones from the pituitary) is treated carefully, as missing hormones must be completely and continuously replaced through replacement medication and additional hormones such as cortisol and thyroid must be augmented in life-threatening situations and surgeries.
