Which one of the following hormones is produced only during pregnancy?

The correct answer is Option (1) → hCG

Option (1) hCG — Correct. hCG (human chorionic gonadotropin) is made by the placenta, which forms only after the embryo implants. So it is found only in a pregnant woman. Pregnancy tests detect this hormone in the urine.

Option (2) Thyroxine — Incorrect. Thyroxine is made by the thyroid gland all through life, in males and females. It controls the rate of metabolism.

Option (3) Cortisol — Incorrect. Cortisol is made by the adrenal cortex all through life. It helps the body deal with stress.

Option (4) Estrogens — Incorrect. The placenta makes estrogens during pregnancy, but the ovary makes them in every menstrual cycle too. So they are not limited to pregnancy.

NCERT Extract:
Pregnancy and Embryonic Development – “… The placenta facilitate the supply of oxygen and nutrients to the embryo and also removal of carbon dioxide and excretory/waste materials produced by the embryo. The placenta is connected to the embryo through an umbilical cord which helps in the transport of substances to and from the embryo. Placenta also acts as an endocrine tissue and produces several hormones like human chorionic gonadotropin (hCG), human placental lactogen (hPL), estrogens, progestogens, etc. In the later phase of pregnancy, a hormone called relaxin is also secreted by the ovary. Let us remember that hCG, hPL and relaxin are produced in women only during pregnancy.”