Macroprolactin's a physiologically inactive form of prolactin found in a small proportion of people. It's in fact prolactin bound to IgG. Macroprolactin's 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 menstrual problems or infertility. There're certain chemicals, such as polyethylene glycol, that can be added to r… (More on Macroprolactin)