How does oxytocin and prolactin control milk secretion in mammals, and what are their roles in lactation?

Sourav PanNovember 9, 2024

Answered

Oxytocin and prolactin are two key hormones that play essential roles in regulating milk secretion during lactation in mammals. Their functions are critical for both the production of milk and the release of milk during breastfeeding. Here’s how each hormone contributes to these processes:

Prolactin

Role in Milk Production

• Stimulates Milk Synthesis: Prolactin is primarily responsible for initiating and maintaining milk production in the mammary glands. It promotes the growth and differentiation of alveolar cells, which are responsible for synthesizing milk components such as lactose, casein, and lipids.
• Hormonal Regulation: During pregnancy, high levels of estrogen and progesterone inhibit the action of prolactin on the mammary glands. After childbirth, the expulsion of the placenta leads to a drop in these hormones, allowing prolactin to exert its effects . This transition marks the beginning of copious milk production, known as secretory activation.

Feedback Mechanism

• Response to Suckling: When a newborn suckles, sensory nerves in the nipple send signals to the hypothalamus, prompting the release of prolactin from the anterior pituitary gland. Prolactin levels peak approximately 30 to 45 minutes after suckling begins and then decrease if suckling does not continue. This feedback loop ensures that milk production is matched to the infant’s needs.

Oxytocin

Role in Milk Ejection

• Milk Let-Down Reflex: Oxytocin is crucial for the milk ejection reflex, also known as let-down. When suckling occurs, oxytocin is released from the posterior pituitary gland into the bloodstream .
• Contraction of Myoepithelial Cells: Oxytocin stimulates contraction of myoepithelial cells surrounding the alveoli in the mammary glands. This contraction increases intra-alveolar pressure, forcing milk into the duct system and out through the nipple . The let-down reflex typically occurs about 30 seconds after suckling begins.

Psychological Factors

• Emotional Bonding: Oxytocin is also associated with emotional bonding and maternal behaviors. The release of oxytocin during breastfeeding enhances maternal-infant bonding, which can further encourage breastfeeding behavior.

Summary of Their Interactions

• Cooperative Function: Prolactin and oxytocin work together to ensure effective lactation. Prolactin promotes milk production while oxytocin facilitates its ejection during breastfeeding. This synergy is crucial for successful nursing and ensuring that infants receive adequate nutrition .
• Positive Feedback Loop: The process creates a positive feedback loop where suckling stimulates both prolactin and oxytocin release, enhancing milk production and ejection with continued breastfeeding