What role does the hormone oxytocin play in the body?

Oxytocin is primarily known for its crucial role in stimulating both lactation and childbirth. During childbirth, it is responsible for causing contractions of the uterine muscles, which helps to facilitate labor. This hormone signals the uterus to contract, thus helping to expel the baby from the womb. Following childbirth, oxytocin also plays an essential role in lactation by promoting the "let-down" reflex, allowing milk to be released from the mammary glands to the nipple for breastfeeding.

The other options lack the specific connection to oxytocin's functions. While growth factors are associated with various hormones including growth hormone, calcium regulation is primarily managed by parathyroid hormone and calcitonin, and blood glucose levels are primarily influenced by insulin and glucagon. Therefore, the unique and critical roles of oxytocin in childbirth and breastfeeding make the second option the most accurate choice.