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 prolactin. It is the most common type of pituitary tumor. Symptoms of prolactinoma are caused either by hyperprolactinemia or by pressure of the tumor on surrounding tissues. In women, these adenomas are often small (<10 mm). In either sex, however, they can become large enough to enlarge the sella turcica. These adenomas represent the most common hormone-producing pituitary tumors and account for 25% to 41% of tumor specimens.[1] MRI is the most sensitive diagnostic test for detecting pituitary tumors(including prolactinoma). Medical therapy for prolactinoma includes dopamine agonists. Surgery is indicated in patients if medical therapy cannot be tolerated. Transsphenoidal resection of tumor is usually done in patients with prolactinoma.
Historical Perspective
Pituitary tumors were first described by Pierre Marie, a French neurologist (Salpetriere Hospital, Paris).
Classification
Prolactinoma can be classified based upon either size or local invasion. Based on size, a prolactinoma can be classified as a microprolactinoma (<10 mm diameter) or macroprolactinoma (>10 mm diameter).
Pathophysiology
Prolactinoma may occur as part of a hereditary disorder called multiple endocrine neoplasia type 1 (MEN 1). A minority of prolactinomas are associated with multiple endocrine neoplasia type I (MEN I), Carney complex, McCune-Albright Syndrome, MEN like syndrome ( CKDN1B loss of function).[2]
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 optic nerve occurs in less than one percent of pregnant women with prolactinoma. In women with large tumors, the risk of damage to the pituitary or optic nerve is greater, and some physicians consider it as high as 25%.
Causes
There are no established causes for proloactinoma. Most pituitary tumors are sporadic, but a minority of tumors are associated with familial syndromes.
Epidemiology and Demographics
The prevalence of prolactinoma in younger age group is 100 per 100,000 individuals.[3] 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 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 increased risk for prolactinoma.
Differentiating prolactinoma from other diseases
Prolactinoma must be differentiated from other diseases that cause hyperprolactinemia including hypothyroidism and side effects of medications(antipsychotics and antidepressants).
Natural History, Complications and Prognosis
If left untreated, 95% of patients with tumor will not show any signs of growth after a 4 to 6 year period. Prognosis is excellent for microprolactinoma. Macroprolactinomas often require more aggressive treatment otherwise they may continue to grow. Most common complications of prolactinoma include intracranial hemorrhage, osteoporosis and vision loss.
History and Symptoms
The common symptoms that the patient may experience 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
Laboratory findings consistent with the diagnosis of prolactinoma include elevated prolactin levels and reduced thyroid hormone levels.
CT Scan
On head CT scan, prolactinoma is characterized by enlargement of pituitary gland.
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
Medical therapy for prolactinoma includes dopamine agonists. Dopamine is the chemical that normally inhibits prolactin secretion. 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 is indicated in patients 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.
References
- ↑ http://www.cancer.gov/types/pituitary/hp/pituitary-treatment-pdq#link/_169_toc
- ↑ http://radiopaedia.org/articles/pituitary-adenoma
- ↑ Ciccarelli A, Daly AF, Beckers A (2005). "The epidemiology of prolactinomas". Pituitary. 8 (1): 3–6. doi:10.1007/s11102-005-5079-0. PMID 16411062.