Final answer:
Option 1: Prolactin(+) is the hormone responsible for stimulating and regulating breast milk synthesis. Prolactin is secreted by the pituitary gland and is part of a positive feedback loop that ensures continued milk production during breastfeeding.
Step-by-step explanation:
The hormone that stimulates and regulates breast milk synthesis is prolactin, making Option 1: Prolactin(+) the correct choice. Prolactin is a pituitary hormone that is essential for the establishment and maintenance of breast milk supply. It also plays a crucial role in the mobilization of maternal micronutrients for breast milk.
During lactation, prolactin-mediated synthesis of milk can vary. Frequent milk removal through breastfeeding or pumping maintains high levels of circulating prolactin over time. Additionally, other hormones like oxytocin, growth hormone, cortisol, parathyroid hormone, and insulin assist in lactation by facilitating the transport of essential nutrients to the breast milk.
During breastfeeding, a positive feedback loop is established when the infant suckles, inducing the hypothalamus to signal the pituitary gland to release more prolactin into the bloodstream. This hormonal signal ensures the continuous production of milk as long as the baby keeps suckling.