Which hormone is primarily secreted by the corpus luteum to support pregnancy if fertilization occurs?

• A. Estrogen
• B. Testosterone
• C. Oxytocin
• D. Progesterone

Answer: (D)

Progesterone is the main hormone produced by the corpus luteum to support early pregnancy. It thickens and maintains the endometrial lining, creating a secretory environment that supports implantation and prevents uterine contractions, helping to sustain the pregnancy. If fertilization occurs, the developing embryo releases human chorionic gonadotropin (hCG), which signals the corpus luteum to continue producing progesterone until the placenta can take over later in the first trimester. Estrogen is produced as well, but progesterone is the primary luteal product for maintaining pregnancy. Oxytocin is related to triggering contractions during labor, and testosterone is not the driver of this luteal support.