Effect of low-dose dopamine on serum concentrations of prolactin in critically ill patients

Dopamine is a naturally occurring catecholamine with actions in the central nervous system and endocrine systems, including inhibition of prolactin release from the pituitary gland. Prolactin secretion has been shown to be increased in response to physiological stress, while hypoprolactinaemia is associated with a reduction in the cellular immune response. We have investigated the effects of low-dose infusion of dopamine 2.5 micrograms kg-1 min-1 on serum concentrations of prolactin in critically ill patients. Six hours after commencing the dopamine infusion, mean serum prolactin concentration had decreased from 746.95 to 128.9 mu. litre-1 (normal range 84-488 mu. litre-1). This represented a mean reduction of 79.2%, with 35% of patients exhibiting a subnormal concentration while receiving dopamine. This reduction was reversed after cessation of dopamine and reproducible on re-institution. This suppression of the release of dopamine may be a detrimental side effect of low-dose dopamine infusion in critically ill patients.