Which hormone, secreted by the pituitary gland, stimulates breast development and milk production?

The hormone that stimulates breast development and milk production is prolactin. This hormone is secreted by the anterior pituitary gland and plays a crucial role in lactation. During pregnancy, prolactin levels increase, which prepares the mammary glands for milk production. After childbirth, prolactin continues to support the production of milk, allowing mothers to breastfeed.

When focusing on other hormones listed in the question: luteinizing hormone (LH) and follicle-stimulating hormone (FSH) are primarily involved in regulating reproductive processes, including ovulation and the menstrual cycle, but they do not directly stimulate milk production. Oxytocin, while important for the milk ejection reflex during breastfeeding, is not responsible for the initiation of milk production itself.