What postpartum event stimulates prolactin release?

• A. Suckling of the infant
• B. Increased physical activity
• C. Exposure to bright light
• D. Sleep

Answer: (A)

Prolactin release is stimulated by nipple stimulation from the infant. When the nipple is stimulated during suckling, neural signals reach the hypothalamus and reduce dopamine inhibition of the anterior pituitary, allowing prolactin levels to rise. This hormone then drives milk synthesis in the mammary glands, supporting ongoing lactation as the baby feeds. Regular suckling keeps prolactin elevated and milk production sustained. The other options do not trigger prolactin release as the primary postpartum event—physical activity, exposure to bright light, or sleep do not initiate lactational prolactin secretion.