Prolactin, Monomeric

Monomeric prolactin is the biologically active form of prolactin. This test helps distinguish true hyperprolactinemia from elevated prolactin levels due to macroprolactin (an inactive, high-molecular-weight form). Monomeric prolactin measurement is useful when total prolactin is elevated but clinical symptoms do not correlate, as macroprolactin can cause falsely elevated total prolactin without biological effects.