Serum prolactin in human immunodeficiency virus infection

Patients infected with human immunodeficiency virus (HIV) have higher serum prolactin compared to healthy controls but this is controversial. As part of a laboratory audit investigating the interference of macroprolactin in our prolactin assay, we investigated whether low biological activity macroprolactin could account for the increased serum prolactin concentrations observed in HIV infection. We, therefore, compared serum total prolactin and free prolactin in 32 subjects infected with HIV (HIV+ve) with 52 subjects not infected with HIV (HIV-ve). Serum total prolactin concentrations were similar in HIV+ve and HIV-ve patients [median (95% confidence limits); 167.0 (122.4 - 313.8) vs 206.5 (187.8 - 248.4) mU/L respectively]. Serum free prolactin concentrations were lower (p <0.005) in HIV+ve subjects than in HIV-ve subjects [112.0 (91.1-141.8) vs 171.0 (154.5 - 200.9) mU/L respectively; p<0.0005]. These results are consistent with the notion that low biological activity macroprolactin contributes to circulating prolactin concentrations in HIV+ve subjects.