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Prolactinoma - What testing will be necessary?

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Hyperprolactinemia is suspected in women who have absent or irregular menstrual periods, abnormal breast discharge, or fertility issues. In men, an elevated prolactin level is suspected in the presence of erectile dysfunction, infertility, headaches, or vision problems.

The first step in the evaluation is to draw a blood sample to determine the prolactin level. The sample can be drawn at any time of day, and a normal level is less than 25 ng/ml in women and less than 17 ng/ml in men. One sample is usually adequate to make the diagnosis. If the prolactin level is just barely elevated, the sample may need to be repeated because even the stress and discomfort of the blood draw itself can affect the results. During the evaluation, your doctor will look for other conditions that could raise prolactin levels and may draw additional blood samples to test other hormone levels.

If your prolactin level is elevated, and all other tests are normal, the next step is to view the pituitary gland by use of a magnetic resonance imaging (MRI) scan with and without contrast dye. The MRI scan will show if there is a tumor on the pituitary, its size, and whether the tumor has affected the optic nerves or other areas around to the pituitary.

The pictures below compare the MRI scans of a microadenoma in a young woman and a macroadenoma in an older man.

MRI1

MRI2

A 31-year old woman presented with absent menstrual periods, abnormal breast discharge, and wanted to get pregnant. Her prolactin level was 125 ng/ml.

A 60-year old man presented with headaches and a low sex drive. His prolactin level was 6,000 ng/ml.

Doctors use different terms to describe the tumor based on its size. Prolactinomas are called MICROADENOMAS if they are smaller than 10 mm (about ½ inch) and MACROADENOMAS if they are 10 mm or larger. Most prolactinomas in women are microadenomas. Prolactinomas in men are more likely to be macroadenomas, although microadenomas are also seen. The large tumors can be associated with extremely high prolactin levels (sometimes greater than 1000 ng/ml). Macroadenomas can push on the optic nerves and men or women with large tumors may need a special eye examination called a formal visual field assessment as part of their initial evaluation. The pictures below compare the MRI scans of a microadenoma in a young woman and a macroadenoma in an older man.