Which hormone, sometimes administered to stimulate labor, is used clinically?

• A. Progesterone
• B. Gonadotropin-releasing hormone
• C. Oxytocin
• D. Cortisol

Answer: (C)

The main concept is how labor can be stimulated pharmacologically. Oxytocin is the hormone used clinically to induce or augment labor because it directly stimulates uterine smooth muscle contractions. It is produced in the hypothalamus and released from the posterior pituitary, and when given exogenously, it binds to oxytocin receptors on the myometrium. This triggers a signaling cascade that increases intracellular calcium, causing rhythmic contractions that help progress labor. Because the dose must be carefully controlled to avoid overly strong or frequent contractions (which can distress the fetus or risk uterine rupture), oxytocin is administered as a carefully titrated IV infusion with monitoring.

The other hormones have different primary roles: progesterone supports pregnancy and tends to keep the uterus relaxed rather than trigger contractions; gonadotropin-releasing hormone drives the release of pituitary gonadotropins but does not directly induce labor contractions; cortisol is a stress-related hormone with no routine use to stimulate labor.