E.B.
My daughter had that show up in blood tests, and she also had symptoms. Prolactin is a hormone. I'm not a medical professional, but from what we were told, a high prolactin level can be the result of certain medications, a thyroid or pituitary gland problem, or other medical conditions.
High prolactin levels, we were told, can result in milk leakage from breasts when there is no pregnancy or breastfeeding, menstruation disruptions (heavy periods, frequent periods or absence of periods, etc).
The type of specialist to see is called an endocrinologist, if the prolactin levels are very high, if there are symptoms, or if there are other elevated levels.
Of course, as with almost all blood test results, everyone's numbers can be slightly higher or slightly lower than other people's. That's why there are averages, or why blood tests have ranges (like, the blood test will have a healthy level that ranges from 2 - 10, or 450 - 525, for example), and that's why it's important to pay attention to symptoms, and to have certain tests repeated if necessary, according to doctor's instructions, to see if there's a pattern or if the abnormal number was just a one-time thing.
With my daughter, it was a matter of stopping a particular medication, after the endocrinologist did further testing to make sure there was no thyroid problem or pituitary gland issue.
If you're concerned, or if the levels are consistently high, if there are symptoms, make sure your child sees the correct specialist (an endocrinologist) and follow through with the doctor's recommendations.