PRL and familial hyperprolactinemia: Second, considering that PRL molecules in serum mainly exist in 3 different forms, namely monomer PRL (23 kD), large PRL (40–60 kD), and macroprolactin (M-PRL) molecule (>150 kD) bound to immunoglobulin G(IgG),[19] When the serum M-PRL concentration exceeds 60% of the total PRL concentration, macroprolactinemia is present,[20] and the prevalence of M-PRL in HPRL patients can be as high as 35%.[21] This patient cannot rule out the possibility of complicating M-PRL.