Prolactinoma overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Faizan Sheraz, M.D. [2]
Overview
A prolactinoma is a benign tumor (adenoma) of the pituitary gland that produces a hormone called prolactin. It is the most common type of pituitary tumor. Symptoms of prolactinoma are caused by too much prolactin in the blood (hyperprolactinemia) or by pressure of the tumor on surrounding tissues. Prolactin stimulates the breast to produce milk during pregnancy. After delivery of the baby, a mother's prolactin levels fall unless she breast feeds her infant. Each time the baby nurses, prolactin levels rise to maintain milk production.
Historical Perspective
Pituitary tumor was first officially described by Pierre Marie, a French neurologist (Salpetriere Hospital, Paris).
Classification
Prolactinoma may be classified according to size into 2 subtypes: microprolactinoma (<10 mm diameter) or macroprolactinoma (>10 mm diameter).
Prolactinoma and Pregnancy
Women with prolactin-secreting tumors may experience further pituitary enlargement and must be closely monitored during pregnancy. However, damage to the pituitary or eye nerves occurs in less than one percent of pregnant women with prolactinoma. In women with large tumors, the risk of damage to the pituitary or eye nerves is greater, and some doctors consider it as high as 25%.
Causes
It has been shown that stress can significantly raise prolactin levels which should make stress a diagnostic differential though it usually is not considered such. Most pituitary tumors are sporadic--they are not genetically passed from parents to offspring.
Epidemiology and Demographics
Autopsy studies indicate that 6-25% of the U. S. population have small pituitary tumors. Forty percent of these pituitary tumors produce prolactin, but most are not considered clinically significant. Clinically significant pituitary tumors affect the health of approximately 14 out of 100,000 people in United States.
Risk Factors
Prolactinoma may occur as part of a hereditary disorder called multiple endocrine neoplasia type 1 (MEN 1), so patients with MEN 1 are at incresead risk for prolactinoma.
Differentiating prolactinoma from other diseases
Hyperprolactinemia caused by prolactinoma must be differentiated from medications(antipsychotics and antidepressants) and hypothyroidism.
Natural History, Complications and Prognosis
Hyperprolactinemia can cause reduced estrogen production in women and reduced testosterone production in men.People with microprolactinoma generally have an excellent prognosis. In 95% of cases the tumor will not show any signs of growth after a 4 to 6 year period. Macroprolactinomas often require more aggressive treatment otherwise they may continue to grow. There is no way to reliably predict the rate of growth, as it is different for every individual. Regular monitoring by a specialist to detect any major changes in the tumor is recommended.
History and Symptoms
The symptoms experienced by women and men are as for hyperprolactinemia from all causes.
Physical Examination
In addition to assessing the size of the pituitary tumor and damage to surrounding tissues it is necessary to perform tests to assess whether production of other pituitary hormones is normal. Depending on the size of the tumor, the physician may request an eye exam with measurement of visual fields.
Laboratory Findings
Prolactin blood levels are tested in women with unexplained milk secretion (galactorrhea) or irregular menses or infertility, and in men with impaired sexual function and, in rare cases, milk secretion.
CT Scan
Computed Tomography (CT scan) is used to visualize changes in the pituitary region of the brain. But it is less sensitive than MRI.
MRI
Magnetic resonance imaging (MRI), is the most sensitive test for detecting pituitary tumors and determining their size. MRI scans may be repeated periodically to assess tumor progression and the effects of therapy. MRI is more sensitive than CT in detecting pituitary tumors.
Medical Therapy
The goal of treatment is to return prolactin secretion to normal, reduce tumor size, correct any visual abnormalities and restore normal pituitary function. As mentioned above, the impact of stress should be ruled out before the diagnosis of prolactinoma is given. Exercise can significantly reduce stress and, thereby, prolactin levels. It should also be noted that higher prolactin levels may contribute to the development of prolactinomas so the diagnosis can be self-fulfilling if the original cause is stress. In the case of very large tumors, only partial reduction of the prolactin levels may be possible.
Surgery
Surgery should be considered if medical therapy cannot be tolerated or if it fails to reduce prolactin levels, restore normal reproduction and pituitary function, and reduce tumor size. If medical therapy is only partially successful, this therapy should continue, possibly combined with surgery or radiation treatment.