23 kDa (small prolactin) | Monomeric, non-glycosylated, high receptor affinity | The main form: biological and immunological |
25 kDa glycosylated forms (G1 and G2) | Carbohydrate unit chains are different | Low immunoreactivity (G2 is 75% more immunoreactive than G1) |
50 kDa (big PRL) | Combination of dimeric and trimeric glycosylated isoforms | Unknown |
100 kDa (big-big PRL) | Probably a G-PRL | Covalently binds to immunoglobulins |