Figure 10.

This diagram illustrates the hypothalamic-pituitary gonadal (HPG) axis in the adult male (the hypothalamus and pituitary, are magnified in the box). DA from the TIDA neurons in the hypothalamus inhibits the release of prolactin from the anterior pituitary. Prolactin acts at the level of the gonad to stimulate sperm and testosterone production. In turn, testosterone feeds back onto TIDA neurons and the pituitary to inhibit the release of DA and prolactin. The green lines represents positive feedback, and the red lines are inhibitory feedback of hormone release and spermatogenesis. Dashed lines designate places where welding fume particulate and associated solubilized metals may interfere with reproductive function.