Prolactin, Total and Monomeric

For males: Prolactin is a pituitary hormone. In men, elevated prolactin can suppress testosterone and contribute to low libido, erectile dysfunction, infertility, and sometimes breast symptoms. Markedly high levels should prompt evaluation for medications or a pituitary cause.

For females: Prolactin is a pituitary hormone involved in breast development and milk production. In women, elevated prolactin can cause irregular or absent periods, infertility, and sometimes breast discharge (galactorrhea). High results should be evaluated for pregnancy, medications, thyroid issues, or a pituitary cause.

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.