Is it My Pituitary?
The pituitary is located in the brain and controls six major hormone systems.
The pituitary, a tear dropped shaped organ in the brain, is about one centimeter in diameter and controls the secretion of most hormones in our bodies. The diagnosis of pituitary dysfunction is made by measuring either subnormal or above normal secretion of particular pituitary hormones. Each hormone must be tested separately and under very specific test conditions because each has a variable pattern of normal secretion.
Pituitary disease will be diagnosed based on symptoms due to structural changes and/or functional changes of the pituitary.
Structural pituitary disease
These diseases can be due to a tumor that develops within the pituiary gland itself or tumors that arise from tissue close to the pituitary gland. Knowledge of pituitary anatomy is important for structural disease. Pituitary gland tumors which can grow over time to become a macroadenoma which is defined as any pituitary tumor 1.0 cm or greater in size. Microadenomas are less than 1.0cm in size.
Pituitary tumors arising from within the pituitary gland itself are almost always benign. The cause of most pituitary tumors are unknown and are generally sporadic in nature. There are several familial disorders that cause pituitary tumors: Mulitple endocrine neoplasia type 1 (MEN1), Carney's syndrome, and Familial isolated pituitary adenoma. There are several other benign tumors and growths that arise in the sella or near the pituitary which include craniopharyngiomas, meningiomas, cysts, abcesses, and ateriovenous fistuals of the cavernous sinus. The rare malignant tumors that can grow within the sella are germ cell tumors, chordomas, lymphoma, or metastatic cancer from another part of the body such as breast and lung cancers. Pregnant women can develop a gnerally benign process called lymphocytic hypophysitis. Any enlarging mass within the sella and parasellar region can cause neurological complications when they physically extend to compress or invade surrounding structures. the endocrinologists will help patients manged the possible neurologic effects of these tumors. These complications can occur at presentation of during followup examinations and can be classified into three large categories:
The major pituitary hormones axes
Cranial nerve deficits
The most common structural complication of these tumors are cranial nerve deficits. In the case of pituitary apoplexy, these deficits can evolve over a period of hours or days but this is a rare occurrence. However, most pituitary adenomas, meningiomas, or craniopharyngiomas evolve very slowly and therefore don't have dramatic changes. Compression of the optic chiasm due to tumors of the sella can cause vision loss usually in a specific pattern called bitemporal hemianopsia. Rarely a patient may develop dyschromatopsia (loss of color vision). Injury to cranial nerves 3,4,or 6 can cause diplopia (double vision). Compression of cranial nerve 5 can cause pain and numbness in the forehead and nose. There are specific simple bedside tests for optic chiasm disease.
Hypothalamic Dysfunction
The hypothalamus controls many brain functions including hunger and sleep-wake cycles. Weight gain and a desire to eat excessively are common manifestations of hypothalamic disease that can occur with tumor invasion or surgical intervention.
Cerebral dysfunction
When the tumor is in the suprasellar location, brain swelling can occur. This swelling can cause subtle changes in how a person walks, their vision, lack of initiative, poor attention. Occasionally patients develop seizures.
Functional pituitary disease
Function pituitary disease can be due to overproduction or underproduction (hypopituitarism) of one or more pituitary hormones. The symptoms from functional pituitary disease are quite variable and completely depend on the pituitary hormone(s) affected. Each hormone has its own "axis" which is a feedback loop from the pituitary gland to a distant endocrine organ. The functional defect can be due to either a pituitary disorder or an end organ disoder. At Houston Thyroid and Endocrine we will take extra time to properly test the appropriate hormones. Each hormone axis secretes hormones in a coordinated and cyclical manner which requires very specific testing protocols.