Macroprolactin

Macroprolactin is a physiologically inactive form of prolactin found in a small proportion of people. It is in fact prolactin bound to IgG.

Macroprolactin is important, as some laboratory assays will detect it as prolactin, leading to a falsely elevated prolactin result. This can lead to a misdiagnosis of hyperprolactinaemia in some people, especially those with other symptoms, such as infertility[1] or menstrual problems.

There are certain chemicals, such as polyethylene glycol, that can be added to remove macroprolactin from a suspicious sample. The sample can then be re-analysed to see if the prolactin levels are still high.

The gold standard test to diagnose macroprolactin is gel-filtration chromatography.