Unraveling Prolactin: The Hormone Behind Milk Production and More

Prolactin (PRL) is a crucial hormone released by the anterior pituitary gland, primarily known for its role in lactation. While its secretion is not as rhythmic as that of growth hormone, PRL levels exhibit episodic surges, especially during sleep. The hormone plays a pivotal role during pregnancy and lactation, where its concentration can rise up to ten times due to increased estrogen levels. This surge is critical for stimulating milk production, illustrating a fascinating positive feedback loop where suckling triggers further prolactin release.

During lactation, prolactin remains elevated as long as the baby continues to suckle. This continuous stimulation not only promotes milk synthesis but also highlights the interconnectedness of hormonal regulation and physical stimuli. The feedback loop continues until the child weans off breastfeeding, demonstrating nature’s efficiency in ensuring adequate nourishment for infants.

However, elevated prolactin levels can lead to health issues, notably hyperprolactinaemia. This condition can disrupt normal menstrual cycles in women, causing oligomenorrhoea or secondary amenorrhoea, and may contribute to sub-fertility by inhibiting the secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Men may experience symptoms like gynaecomastia or secondary hypogonadism, often linked to larger pituitary tumors known as macroadenomas.

Diagnosing hyperprolactinaemia involves careful assessment, as stress from blood draws can artificially inflate prolactin levels. Multiple blood samples are typically required to establish a reliable diagnosis, and the presence of macroprolactin—an inactive form of the hormone—can complicate the picture. Proper laboratory methods are essential to differentiate between active and inactive prolactin to avoid misdiagnosis.

For effective management, understanding the underlying causes of elevated prolactin is key. Microprolactinomas are often responsible for increased PRL levels in women of reproductive age, while men and postmenopausal women may present with more advanced conditions. The treatment approach may vary depending on the specific diagnosis, emphasizing the importance of thorough investigation.

Prolactin’s influence extends beyond lactation; it also plays roles in the regulation of the immune system and reproductive processes. With ongoing research, our understanding of this multifaceted hormone continues to evolve, highlighting its importance in both physiological and pathological contexts.