I have been diagnosed with hyperprolactinemia and have been scheduled for an MRI to see if any adenomas are present. What else can cause high levels of prolactin? Will I need to take medications for this continually? Any information about this topic will be appreciated!

-- Melinda

Prolactin is one of many hormones produced by the pituitary gland. It is primarily responsible for milk production during lactation.

The pituitary's hormone production rises and falls depending on hormonal instructions from another gland, the hypothalamus. In the case of most pituitary hormones, including FSH and LH, the presence of hypothalamic hormones signals the pituitary to increase production. For prolactin, however, the signal works in reverse: An increase in the hypothalamic hormone dopamine tells the pituitary to stop releasing prolactin. In some cases, however, the dopamine cannot reach the pituitary gland by passing through the veins of the pituitary stalk. When that happens, there's no signal to suppress the secretion of prolactin, and the pituitary continues to release prolactin.

When prolactin levels rise, the hypothalamus manufactures and releases more dopamine in an effort to stop prolactin production. This increase in dopamine has other effects. In particular, it suppresses the hypothalamus' production of the hormones that promote release of FSH and LH. This, in turn, leads to a drop in LH and FSH, causing low estrogen levels and amenorrhea (lack of menstrual periods).

High prolactin levels can often cause both amenorrhea (absent or irregular menses) and galactorrhea (milk production from the breast). Some common causes for prolactin elevation include:

-- pregnancy
-- a type of pituitary tumor (growth) that produces prolactin
-- stress, exercise, nipple stimulation, chest wall lesions (scars, pacemakers), or sexual stimulation
-- medications such as certain blood pressure medications, anti-nausea drugs or antipsychotics
-- kidney failure
-- cirrhosis of the liver
-- primary hypothyroidism (underactive thyroid gland)
-- compression of the pituitary stalk from tumors, empty sella syndrome or sarcoidosis

An MRI test or CT scan enables a radiologist to see if a tumor is present or if compression of the pituitary stalk is causing the problem. There is presently some controversy as to when the MRI or CT scan is necessary, and in the current cost-cutting climate, the use of these types of tests is being evaluated with a more critical eye. One rationale is this: Levels of prolactin above 100ng/ml are usually due to prolactin-secreting pituitary tumors. Pituitary tumors and other forms of hyperprolactinemia (elevated levels of prolactin) are treated with the same medications, so it would seem that the scan adds little benefit and offers no insight into treatment choices. If the tumor is large, however, it may press on the optic nerve fibers and cause visual defects. So if you have headaches or visual problems along with hyperprolactinemia, an MRI scan is a must.

What about patients with lower levels of prolactin that are still above normal? The first thing we do is repeat the blood test early in the morning in a nonstressed setting. If the elevation persists, and if thyroid disease or medications have been ruled out as causing the elevated prolactin, the MRI may be helpful in making sure the pituitary stalk is not compressed by tumors or other masses. Smaller tumors are called microadenomas. If they are larger than one centimeter in size, they are called macroadenomas.

Pituitary tumors in general are not rare at all. Autopsies show that up to 10 percent of people have some sort of pituitary tumor. So don't be alarmed if your doctor wants to check for a pituitary tumor. Still, most women with prolactin elevations do not have a pituitary tumor. When they do, the condition is usually easily treated with medication; surgery is rarely needed.

There are two medications commonly used. Parlodel is a pill taken two or three times per day. The dosage must be increased gradually to minimize the risk of postural hypotension (dizziness when changing positions). Upset stomach is also not unusual with this medication. A novel approach to minimize these side effects is to administer the tablet via the vagina.

Dostinex (cabergolide) is a pill taken twice weekly. While postural hypotension and nausea can still be seen, many who cannot tolerate Parlodel find Dostinex acceptable. This medication is considerably more costly.