Negative Feedback Loops of the Male HPG Axis

The hypothalamic-pituitary-gonadal (HPG) axis is the hormonal system that controls male reproduction. The hypothalamus secretes GnRH, the pituitary responds with LH and FSH, and the testes produce testosterone and support sperm production, with feedback signals keeping hormone levels balanced.

In males, luteinizing hormone (LH) acts on the Leydig cells of the testes. Binding of LH stimulates these interstitial cells to synthesize and secrete testosterone, which then circulates to support spermatogenesis and exert negative feedback on the hypothalamus and pituitary.

Rising testosterone feeds back on both the hypothalamus and the anterior pituitary, reducing the release of GnRH and therefore LH and FSH. This negative-feedback loop lowers further testosterone production, keeping the hormone within a stable physiological range.

Follicle-stimulating hormone (FSH) acts on the Sertoli cells of the testes to support spermatogenesis. Sertoli cells also release inhibin, which selectively feeds back on the pituitary to suppress FSH, complementing the testosterone feedback that acts on both the pituitary and hypothalamus.

You can generate an HPG axis diagram on SciFig: describe the hypothalamus, pituitary, and gonads with their hormones, and SciFig produces an editable figure showing GnRH, LH, FSH, testosterone, and the negative-feedback arrows. You can then relabel each part and export it.

Yes. After generating the diagram you can open it in SciFig's editor to vectorize it into clean SVG, relabel the hypothalamus, pituitary, gonads, and hormones, adjust the feedback arrows, and export it in the format your paper, poster, or slide requires.