Check for cancer

Testicular germ cell tumors

Not sure if joking or not

Partly true apparently but by no means reliable http://www.snopes.com/medical/disease/pregnancytest.asp

You can be a woman and have it happen to you as well. There has been times where women thought they were pregnant only to find out they had cancer.

Little known fact: If you jizz on your positive pregnancy test and it turns negative, you're cured!