Why do my testes move up and become rigid sometimes?

Q: I am 30 Years old. About 10 years back my testes became completely descended to the maximum extent possible. Whenever I go to toilet, my testes move up and become hard and rigid. After about 10 or 20 minutes, they come down. What is this all about? Will it affect fertility? Please clarify.

A:The scrotal skin has property to expand or shrink depending on the weather or otherwise. This is protective mechanism nature has made for management of temperature. Don't worry.