Which hormone is primarily responsible for milk production?

Prolactin is the hormone primarily responsible for milk production in lactating females. It is secreted by the pituitary gland and plays a critical role in the development of mammary glands and the stimulation of milk synthesis. After childbirth, elevated prolactin levels promote breast milk production, ensuring that the newborn receives adequate nutrition through breastfeeding.

Thyroxin, while important for regulating metabolism and energy levels, does not have a direct role in milk production. Oxytocin is involved in the milk ejection reflex during breastfeeding, helping to release milk from the mammary glands into the ducts, but it does not initiate or sustain the production of milk. Aldosterone primarily regulates sodium and potassium balance and blood pressure, having no significant impact on milk production. Thus, prolactin is the correct answer as it directly stimulates the mammary glands to produce milk.