What hormone is produced in response to infant suckling that stimulates milk production?

Prolactin is the hormone that plays a pivotal role in lactation, specifically in response to infant suckling. When a baby suckles at the breast, nerve endings in the nipple are stimulated, which sends signals to the hypothalamus and then to the pituitary gland. In response, the pituitary gland releases prolactin into the bloodstream. This hormone is crucial for the production of milk in the mammary glands.

As prolactin levels increase, milk synthesis and secretion are stimulated, ensuring that the infant receives adequate nutrition. Breastfeeding not only facilitates bonding between the mother and infant but also promotes the appropriate hormonal responses to support lactation effectively.

Other hormones mentioned, such as estrogen and testosterone, are important in sexual development and reproduction but do not directly stimulate milk production in response to suckling. Insulin is primarily involved in glucose metabolism and does not play a direct role in milk production either. Thus, prolactin is specifically responsible for the initiation and maintenance of milk production in lactating women, making it the correct choice for this question.