In Depth Protocol

The testicles hang outside the body because the enzymes required for sperm and testosterone production (in Leydig and Sertoli cells) denature at core body temperature (37°C). The Bull Study: Leydig cells (which produce Testosterone) are extremely heat-sensitive. As shown in animal models, artificially raising scrotal temperature by just ~3°C for 48 hours resulted in 90% less testosterone in the blood. Sitting down: Healthy scrotal temperature ~34.2°C, can rise up to ~36.5°C (near core body temp) while sitting in a car Action: Ventilate, move to disipate heat, wear boxes, sleep cool. Keep 'em cool.