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Prolactinomas are pituitary adenomas that secrete prolactin, a hormone which controls lactation, among other things. Prolactinomas are the most common pituitary adenoma. Prolactin levels in patients with prolactinomas are often elevated, in correlation to the size of the tumor.
In most women, prolactinomas are detected when they are small (microadenomas) and when the prolactin level is only moderately elevated (50 – 300 ng/ml).
These moderate elevations in prolactin level can cause menstrual irregularities or milk production in the breasts. Most distressingly, they cause infertility.
In men, prolactinomas are typically larger at time of detection, and prolactin levels are often over 500 – 1000 ng/ml. The larger tumors damage the rest of the pituitary, causing lower levels of other hormones (Hypopituitarism), often leading to shrinking of the tested (hypogonadism). Headache and visual loss can occur. Rarely, patients may hemorrhage into a tumor causing rapid onset of headache, visual loss, double vision, and pituitary failure (pituitary apoplexy).
Women and men both often complain of reduced sex drive (libido) and weight gain.
A prolactinoma is diagnosed by demonstrating elevated blood prolactin levels.
Prolactin levels over 150 ng/ml are almost always due to a prolactinoma.
Moderate prolactin elevations (30-150 ng/ml) can be secondary to:
- low thyroid function (hypothyroidism)
- kidney or liver failure
- medications (e.g., haloperidol, antidepressants, verapamil)
- stalk compression effect” from a pituitary or brain tumor that compresses the pituitary stalk
- other adenomas, craniopharyngiomas, Rathke’s cleft cysts and other brain tumors
Prolactinomas can be best visualized on a pituitary MRI performed with and without Gadolinium.
- Medical Therapy: Medication is the first line treatment for patients with a prolactinoma. Twice weekly cabergoline (Dostinex), or other dopamine agonists normalize prolactin levels in about 80% of patients. Most women enjoy a return of menses and fertility. Vision and headache can rapidly resolve with tumor shrinkage, in more than half of patients. Long-term higher-dose therapy with cabergoline or bromocriptine raises the risk of heart valve problems. It is unclear whether the lower doses used in the treatment of prolactinomas carry similar risks.
- Endonasal Endoscopic Surgery: In patients with microprolactinomas which do not invade the cavernous sinus, with prolactin levels <250 ng/ml surgery leads to long term remission about 90% of the time. For invasive macroprolactinomas, or for prolactinomas with prolactin levels over 1000 ng/ml, the surgical cure rate is less than 30%. Even in patients with longstanding vision loss cabergoline can be tried first. If vision loss occurs rapidly, or if there is evidence on MRI of subacute hemorrhage, endonasal surgery for tumor debulking is generally recommended.
- Radiosurgery (SRS) or Stereotactic Radiotherapy (SRT): Even in patients with large, unresectable and medically refractory prolactinomas, cure can often be achieved with stereotactic radiotherapy such as Cyberknife. A recent report from the University of Pittshbugh in such patients showed a cure rate (normal serum prolactin level off medications) of 27.3%. These results compare very favorably to surgical series. 54% had endocrine improvement (decreased but still elevated serum prolactin level) Less than 20% experienced further progression of their disease. The tumor shrank and did not grow back in 86.4% of patients. For patients who hope to discontinue medical treatment, and who do not want to undergo the risks of surgery, radiosurgery such as Cyberknife is an excellent option. http://www.ncbi.nlm.nih.gov/pubmed/22302560