The temperature in the scrotal sac normally ranges between 94 and 96 degrees fahrenheit . When the temperature rises above 96 degrees sperm production decreases, sometimes very significantly. Many factors can increase scrotal temperature such as tight shorts, tight jeans, as well as tight bikinis. It has also been postulated that certain exercises such as jogging and use of rowing machines can cause an increase in scrotal temperature so that it is important to allow the scrotum to cool down afterwards. There are devices that can be purchased for this as well as merely using a cool shower.
Varicoceles occur more often in infertile men than in males who are fertile.
This is regulated by certain hormones including testosterone and mullerian inhibiting factor. When they do not descend normally before the second year of life they are referred to as cryptorchid testes and subsequently are subject to a higher temperature and other insults to the blood supply. Most of the time they will descend within the first year of life. Approximately 1 in 300 men with this condition will not have their testes descend. This condition may not be diagnosed until an adult.