Do hormones make men think of sex?
Interestingly it does seem as if this is at least in part the case.  

Testosterone levels are tied to sexual impulses, but also risky behavior and aggression.  Its responsible for sexual drive in women as well.  Low testosterone can cause depression and loss of the ability to make decisions.  

You'll note that the work cited is done on criminals, patients and rats.  Remember that is not medically or scientifically ethical to change the androgen levels of a functioning human being.  Testosterone supplements might increase the chances of prostate cancer.  

While its not scientific, there's a fascinating set of interviews about how testosterone affects human thinking at this transcript of American life, Act 2 :


  After testosterone, there was no narrative. There was no language
  whatsoever. It was just, I would see a woman who was attractive or not
  attractive. She might have an attractive quality, nice ankles or
  something, and the rest of her would be fairly unappealing to me.
  
  But that was enough to basically just flood my mind with aggressive,
  pornographic images, just one after another. It was like being in a
  pornographic movie house in my mind. And I couldn't turn it off. I
  could not turn it off. Everything I looked at, everything I touched,
  turned to sex.