Macroprolactinaemia refers to a polymeric form of prolactin in which several molecules form aggregates with circulating IgG. This rarely elicits a biological response due to the inability of such a large molecule to interact with the prolactin receptor, however, it can be detected by immunoassays leading to spurious elevated prolactin results.
Differential diagnosis of macroprolactin-associated hyperprolactinaemia with that of prolactinoma, hypothyroidism or drug/stress-induced hyperprolactinaemia, eg. Assayed prolactin >600 mIU/L (female) or >350mIU/L (male) where physiological or pathological causes of hyperprolactinaemia are excluded
SST (gold top) or serum (red top)