Prolactin

Overview

Prolactin is a hormone primarily produced by the anterior pituitary gland, best known for its essential role in lactation and breast development during pregnancy. Beyond its lactogenic function, prolactin influences over 300 physiological processes including reproductive health, metabolism, immune regulation, fluid balance, and behavior. It is also produced in other tissues such as the uterus, brain, immune cells, and adipose tissue. Tracking prolactin levels is important for assessing reproductive function, diagnosing pituitary disorders, and evaluating causes of infertility or abnormal lactation.

Scientific Background

Prolactin is a protein hormone structurally related to growth hormone and placental lactogen, consisting mainly of a 23-kDa single-chain polypeptide. It is secreted by lactotroph cells in the anterior pituitary and regulated by hypothalamic dopamine, which inhibits its release. Prolactin secretion increases during pregnancy and breastfeeding to stimulate mammary alveoli development and milk production. Besides the pituitary, prolactin is synthesized in various tissues, contributing to its diverse roles. Different molecular forms exist, including little prolactin (biologically active), big prolactin, and macroprolactin (less active). Prolactin interacts with other hormones such as estrogen, progesterone, and dopamine, and its levels correlate with reproductive and metabolic biomarkers.

Measurement and Testing

Prolactin levels are measured via blood tests, typically using immunoassays. Testing is recommended when symptoms like unexplained lactation, menstrual irregularities, infertility, or erectile dysfunction occur. Factors affecting results include stress, time of day (levels peak during sleep), pregnancy, medications (e.g., antipsychotics), and pituitary tumors. To avoid false elevations, blood samples are often taken fasting and at rest. Repeat testing may be necessary to confirm abnormal results.

Reference Ranges

Normal prolactin levels vary by sex, age, and physiological state. Typical reference ranges are approximately 4.8–23.3 ng/mL for nonpregnant women and 4.0–15.2 ng/mL for men, though ranges differ slightly by laboratory. During pregnancy and breastfeeding, prolactin levels rise significantly, often exceeding 200 ng/mL. Levels also vary with age and circadian rhythm. Values must be interpreted in context, considering clinical symptoms and physiological conditions.

High Values

Hyperprolactinemia (elevated prolactin) can result from prolactin-secreting pituitary adenomas (prolactinomas), hypothyroidism, kidney disease, chest trauma, or certain medications (e.g., antipsychotics, antidepressants). High prolactin disrupts reproductive function, causing menstrual irregularities, infertility, galactorrhea (milk production outside breastfeeding), decreased libido, and erectile dysfunction. Large pituitary tumors may cause headaches and visual disturbances. Persistent elevation warrants evaluation for underlying causes and potential treatment.

Low Values

Low prolactin levels are less common and may occur due to pituitary insufficiency or hypothalamic dysfunction. Deficiency can impair lactation postpartum, leading to insufficient milk production. It may also reflect broader pituitary hormone deficiencies. Symptoms related to low prolactin are generally subtle but can impact breastfeeding success and reproductive health.

Improving Biomarker Levels

Management of abnormal prolactin depends on the cause. For high prolactin due to prolactinomas, dopamine agonists (e.g., bromocriptine) effectively reduce levels and tumor size. Addressing hypothyroidism or discontinuing causative medications can normalize prolactin. Lifestyle factors such as stress reduction and adequate sleep may help regulate levels. For low prolactin affecting lactation, support with lactation consultants and addressing underlying pituitary issues is important. Supplements are not typically used to modify prolactin directly.

Importance of Tracking

Monitoring prolactin levels aids in diagnosing and managing reproductive disorders, pituitary tumors, and causes of abnormal lactation. It guides treatment decisions, helps assess therapy effectiveness, and prevents complications such as infertility or tumor progression. Regular tracking is especially important in symptomatic individuals or those with known pituitary abnormalities.

Disclaimer

The information provided in this document is for educational purposes only and does not constitute medical advice. It is essential to consult with a qualified healthcare professional for any health concerns or before making any decisions related to your health or treatment.