Prolactin is a peptide hormone secreted by lactotroph cells in the anterior pituitary gland. It is classified as a pituitary endocrine factor primarily recognized for its role in promoting mammary gland development and milk production. Historically it was identified by its effect on lactation, and it remains the central laboratory marker tied to that biological pathway. Beyond lactation, prolactin interacts with reproductive hormones and has modulatory effects on immune cells and metabolism. It participates in feedback loops with the hypothalamus and other endocrine organs, so its circulating level can reflect broader changes in neuroendocrine regulation rather than a single isolated process.

Elevated prolactin levels may reflect increased pituitary secretion or altered regulatory signals. Common associations include pregnancy and breastfeeding, recent physical or emotional stress, sleep, chest wall stimulation, changes in thyroid function, and certain medications that influence dopamine pathways. Interpreting a high value requires context from menstrual, reproductive, thyroid, and medication history plus other hormones on the panel. Low prolactin levels may indicate reduced pituitary output or stronger inhibitory signaling (for example, from dopamine-related pathways or some medications). Low values are less common but can be seen with pituitary suppression, certain drugs, or other endocrine patterns. Any single prolactin result should be read alongside the full Foundation Zoomer report and clinical history for accurate pattern recognition.

Prolactin is included in the Foundation Zoomer to evaluate pituitary and reproductive endocrine balance and to show how lactation-related signaling interacts with thyroid, sex hormones, stress markers, and metabolic measures. Its value helps clinicians identify hormonal patterns that may explain symptoms and guides targeted follow-up and personalized care planning.