Synthetic analogues of human sex hormones.

• A. Oral contraceptives
• B. Diazepam
• C. Morphine
• D. Hepatitis B vaccine

Answer: (A)

Synthetic analogues of human sex hormones are drugs that mimic the actions of estrogen and progesterone to regulate the reproductive system. Oral contraceptives typically combine a synthetic estrogen with a synthetic progestin (or use progestin alone). By providing these hormones, they suppress the hypothalamic-pituitary-ovarian axis, reducing FSH and LH release and preventing ovulation. They also alter cervical mucus and the endometrium, making fertilization and implantation less likely. This is why they’re used as a birth-control method and can aid in cycle regulation and other hormone-related conditions. The other options are not hormone analogues: diazepam is a benzodiazepine, morphine is an opioid analgesic, and the hepatitis B vaccine is a vaccine, not a hormone mimic.