Prolactin is produced by the anterior pituitary and has several functions, including supporting milk production. Its regulation differs from many pituitary hormones because dopamine provides an important ongoing inhibitory influence. Blocking D2 receptors can remove part of this restraint and increase prolactin secretion.
Hyperprolactinaemia means an elevated level of prolactin, a hormone produced by the pituitary gland. Dopamine normally restrains prolactin release, so some D2-blocking medicines can increase it. Other physiological, medical and medication causes also exist. A raised result requires interpretation in context rather than automatic attribution to an antipsychotic or a single disease.
Levels also vary with physiological circumstances, stress and other influences. Pregnancy and breastfeeding are important contexts, while some medical conditions and medicines can elevate prolactin. A laboratory result therefore needs interpretation alongside history and symptoms. The hormone is not simply a direct measure of dopamine throughout the brain. Understanding regulation explains why a medicine can help psychosis yet affect sexual or reproductive function through another system. It also shows why different antipsychotics can have different prolactin effects even when they all involve D2 receptors in some way.
A hormone result is interpreted against its physiological context and the laboratory’s method. Stress and sampling conditions can influence findings, while reproductive circumstances may change what is expected. This is why a single result may need clarification rather than immediate attribution. The clinical question is whether elevation is persistent, symptomatic and adequately explained by the available history and investigations.
Further reading: DailyMed prescribing information (1); DailyMed prescribing information (2).
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