What are the parts of the HPG axis?

• A. Cerebellum, medulla, and pons.
• B. Hypothalamus, pituitary gland, and gonads (testes and ovaries).
• C. Liver, pancreas, and spleen.
• D. Thyroid, parathyroid, and adrenal glands.

Answer: (B)

Think of the HPG axis as the command line that coordinates puberty and reproductive development. It starts in the hypothalamus, which releases GnRH. GnRH then prompts the pituitary gland to secrete two gonadotropins, LH and FSH. Those hormones travel to the gonads—the testes in males and the ovaries in females—where they stimulate the production of sex hormones (testosterone or estrogen/progesterone) and kick off gamete production. The sex hormones feed back to the hypothalamus and pituitary to fine-tune the system, creating a regulatory loop. So the parts of the HPG axis are the hypothalamus, the pituitary gland, and the gonads. Other options reference brain regions or glands that aren’t arranged in this hypothalamus–pituitary–gonad sequence.