Which organ produces the female sex hormones progesterone and estrogen that influence the menstrual cycle?

• A. Ovaries
• B. Testicles
• C. Pancreas
• D. Parathyroid

Answer: (A)

The ovaries are the primary source of the female sex hormones progesterone and estrogen, which regulate the menstrual cycle. Estrogen helps build up and thicken the uterine lining in the first half of the cycle and also contributes to the hormonal signals that trigger ovulation. Around mid-cycle, estrogen supports a surge in LH that leads to ovulation. After release of the egg, the corpus luteum in the ovary secretes progesterone, which stabilizes and maintains the uterine lining in case pregnancy occurs. If there isn’t a pregnancy, the corpus luteum fades, progesterone and estrogen decline, and the lining is shed during menstruation. The other organs listed don’t produce these hormones in meaningful amounts—testicles mainly produce testosterone, the pancreas makes insulin and glucagon, and the parathyroid glands regulate calcium.