Final answer:
The hormone secreted by the pituitary gland that initiates and maintains milk secretion is prolactin.
The hormone secreted by the pituitary gland responsible for initiating and maintaining milk secretion is prolactin (PRL).
Step-by-step explanation:
The hormone that is secreted by the pituitary gland that initiates and maintains milk secretion is prolactin (PRL). This hormone, produced by the anterior pituitary, is instrumental in the establishment and maintenance of breast milk supply. Prolactin is also important for the mobilization of maternal micronutrients for breast milk, making it essential for the postpartum period of lactation.
When a baby begins suckling at the breast, nerve impulses reach the hypothalamus, which in turn stimulates the anterior pituitary to release prolactin. This hormone then travels through the bloodstream to the mammary glands, stimulating them to produce milk. Moreover, the production of prolactin is regulated by a positive feedback loop, continuing as long as the baby suckles, and the interplay between prolactin-releasing hormone (PRH) and prolactin-inhibiting hormone (PIH), which is dopamine, controls its release.