Prolactin, a hormone produced by the pituitary gland located at the base of the brain, plays a multifaceted role in the human body. While often associated primarily with milk production, this versatile hormone influences various physiological functions in both males and females. Its presence and levels are indicative of different bodily processes, extending beyond reproductive health.
Role in Lactation and Reproduction
Prolactin’s most recognized function lies in its role in lactation and female reproduction. During pregnancy, prolactin levels gradually increase, stimulated by hormones like estrogen and progesterone, which prepare the mammary glands for milk production. After childbirth, the rapid decline in estrogen and progesterone, coupled with the baby’s suckling, triggers the sustained production of breast milk.
The continuous suckling stimulus maintains elevated prolactin levels, ensuring a steady supply of milk for the infant. Beyond milk production, prolactin also influences the female reproductive cycle by suppressing ovulation during breastfeeding. This suppression, known as lactational amenorrhea, acts as a natural contraceptive mechanism in the postpartum period. The higher prolactin levels inhibit the release of gonadotropin-releasing hormone (GnRH), delaying the return of regular menstrual cycles and fertility. The effectiveness of this natural contraception varies with breastfeeding intensity and frequency, particularly with nighttime feedings.
Functions Beyond Lactation
Prolactin’s influence extends far beyond its reproductive and lactation-related roles, impacting several other bodily systems. It acts as an important regulator of the immune system. Prolactin also plays a part in metabolism, affecting how the body processes energy and regulates body weight. Studies suggest it can influence lipid synthesis in different cell types, such as mammary and adipose cells.
This hormone also impacts behavior, including stress responses and parental bonding. Prolactin has been linked to maternal behavior and can influence anxiety-related behaviors. It may contribute to the accumulation of fat, a biological adaptation to support the energetic demands of pregnancy and lactation. Research indicates that prolactin can act as a growth, differentiating, and anti-apoptotic factor, with roles in hematopoiesis and angiogenesis.
Prolactin in Males
While often seen as a hormone primarily for females, prolactin also serves distinct functions in the male body. It influences testosterone production and supports overall reproductive health in men. The hormone also plays a role in spermatogenesis, the process of sperm development.
Elevated prolactin levels in males can impair sperm production by interfering with hormonal signals necessary for normal sperm maturation. This interference can result in reduced sperm count, motility, and abnormal morphology, contributing to male infertility. Prolactin is also involved in male sexual function, influencing sexual satisfaction and recovery after orgasm.
Imbalances in Prolactin Levels
Abnormal prolactin levels can lead to various health concerns, with hyperprolactinemia (high prolactin) being more commonly diagnosed than hypoprolactinemia (low prolactin). Hyperprolactinemia occurs when prolactin levels exceed the normal range. One common cause is a prolactinoma, a benign pituitary tumor that produces excess prolactin. Other causes include certain medications, such as antipsychotics and antidepressants, hypothyroidism, and chronic kidney or liver disease.
In women, hyperprolactinemia often manifests as irregular menstrual periods or amenorrhea, which is the complete absence of menstruation. It can also cause galactorrhea, the unexpected production of breast milk unrelated to pregnancy or breastfeeding. These hormonal disruptions can lead to infertility by interfering with normal ovulation. Men with high prolactin levels may experience decreased libido, erectile dysfunction, and sometimes galactorrhea. Both sexes might also develop headaches and visual disturbances if a pituitary tumor is present.
Conversely, hypoprolactinemia is less common and often presents with fewer overt symptoms. The most direct consequence in women is insufficient milk production after childbirth, potentially impacting newborn nutrition. Low prolactin levels can result from pituitary gland damage, certain medications like dopamine agonists, or other hormonal imbalances. In men, low prolactin may contribute to reduced fertility, though this is less frequent than with elevated levels.