The pituitary gland is a small organ with a major function. From within the brain, it controls production of hormones by other endocrine glands. Like other structures in the body, the pituitary gland can be prone to tumorous growth.
The Normal Pituitary Gland
The pituitary gland is a pea-shaped structure located at the base of the brain. It hangs beneath a brain structure called the hypothalamus and is cradled in a bony portion of the skull called the sella turcica. The gland is also in the vicinity of the optic chiasm, a neural structure formed by the optic nerves from the eyes.
The hormones produced by the pituitary gland are as follows:
- Adrenocorticotrophic hormone (ACTH) to stimulate production of cortisol from the adrenal glands
- Antidiuretic hormone (ADH), also called vasopressin, to help maintain body water
- Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) to regulate the reproductive glands
- Oxytocin to stimulate contraction during labor and breastfeeding in women
- Prolactin to help produce breast milk in women
- Somatotropin, also called growth hormone, to enable cellular growth
- Thyroid-stimulating hormone (TSH) to boost production of thyroid hormone by the thyroid gland
Nonfunctional Pituitary Tumors
A pituitary gland tumor that does not overproduce a specific hormone can still cause symptoms. One of the most common is visual impairment. The tumor can compress the optic chiasm, causing blindness in the far left and right sides of the visual field. Headache may also be a symptom.
Functional Pituitary Tumors
A functional pituitary tumor is one that secretes a particular hormone. Besides the symptoms and signs related to tumor compression, patients may have other symptoms depending on which hormone is overproduced:
- Corticotrophic Adenoma: Overproduction of ACTH, and therefore cortisol, leads to Cushing's disease, characterized by obesity with central distribution and a moon-like face, diabetes, high blood pressure, stretch marks and bruises in skin, and osteoporosis.
- Prolactinoma: Excess production of prolactin leads to absent menstrual periods (amenorrhea), overproduction of breast milk (galactorrhea), and infertility in women and to decreased libido in men
- Somatotrophic Adenoma: Too much growth hormone leads to acromegaly, with enlargement of the face, hands, and feet. Patients may also have elevated blood glucose and muscle weakness.
- Thyrotrophic Adenoma: Elevated levels of TSH may lead to overproduction of thyroid hormone and cause symptoms of hyperthyroidism, such as heat intolerance and weight loss
Hormone Deficiency
Pituitary tumors can also cause deficiency in hormones if the tumor compresses the gland and prevents secretion. The manifestations of hormone deficiencies are beyond the scope here.
Treatment
Medications are available to address elevations of certain hormones. Surgical resection of the tumor, usually with a transsphenoidal approach up the nose and through the base of the skull, can be curative. After surgery, replacement of deficient pituitary hormones may be needed.
