Which hormone stimulates the anterior pituitary to secrete FSH and LH?

• A. Estrogen
• B. Progesterone
• C. Prostaglandin
• D. GnRH

Answer: (D)

Gonadotropin-releasing hormone from the hypothalamus is the signal that prompts the anterior pituitary to release FSH and LH. It travels to the pituitary in pulses and binds to GnRH receptors on gonadotroph cells, triggering a signaling cascade that leads to both the release of stored LH and FSH and the production of their subunits. This pulsatile stimulation is key; if GnRH is given continuously, the pituitary becomes less responsive and gonadotropin release falls.

Estrogen and progesterone mainly act as feedback regulators of the hypothalamus and pituitary, shaping GnRH and gonadotropin release but not serving as the direct stimulus to secrete FSH and LH. Prostaglandins are local mediators with various roles in inflammation and other tissues, not the primary driver of anterior pituitary secretion of FSH and LH.

So the hormone that directly stimulates the anterior pituitary to secrete FSH and LH is GnRH.