Which hormone is essential for inducing uterine contractions and ejection of milk?

Oxytocin is the hormone that plays a crucial role in stimulating uterine contractions during childbirth and facilitating the ejection of milk during breastfeeding. This hormone is produced in the hypothalamus and released by the posterior pituitary gland. During labor, oxytocin levels increase and enhance uterine muscle contractions, helping to move the baby through the birth canal. Additionally, during lactation, oxytocin is triggered by the suckling reflex, causing the milk to be released from the mammary glands, making it available for the infant.

Prolactin, while also important in the context of milk production, primarily stimulates milk synthesis rather than its ejection. Cortisol is a glucocorticoid hormone that plays a key role in the body's stress response and metabolism but is not directly involved in uterine contractions or lactation. Testosterone is primarily associated with male reproductive functions and does not have a role in inducing contractions or milk ejection. Thus, oxytocin is specifically linked to these physiological processes, making it the essential hormone in this context.