Which gland releases oxytocin, stimulating the mammary gland?

The pituitary gland is responsible for the release of oxytocin, which plays a crucial role in stimulating the mammary glands during lactation. Oxytocin is often referred to as the "love hormone" and is released in response to various stimuli, including the suckling of a calf or the presence of an infant. When oxytocin is released into the bloodstream, it promotes the contraction of myoepithelial cells around the alveoli in the mammary gland, leading to the ejection of milk. This physiological process is essential for breastfeeding and successful lactation.

While the thyroid, adrenal, and pineal glands have important functions in the body—including regulation of metabolism, response to stress, and sleep cycles, respectively—they are not involved in the direct stimulation of the mammary gland through the release of oxytocin. Therefore, the pituitary gland's role in releasing this hormone makes it the correct answer in the context of milk production and the lactation process.