There are plenty of benefits to a plentiful amount of male hormone, such as increased energy, alertness and muscle tone. Unfortunately, hormones also play a role in abnormal cell reproduction -- particularly for men. Cancer cells in the prostate, for example, are fueled by testosterone. This makes the indiscriminate use of testosterone creams and other replacement therapies a genuine health concern. Testosterone replacement therapy alone grew more than 24 percent from 2005 to 2009, the year it reached $838 million in annual sales [source: Research and Markets]. Before men add synthetic testosterone to their systems, they should undergo testing to be sure prostate cancer cells are present. About half of men age 50 and older probably have cancer cells lurking in their prostate [source: Harvard Medical School].
It also pays to pay attention to another hormone -- melatonin -- regardless of gender. This hormone regulates your internal clock, and is the reason you become sleepy at night and wakeful in the morning. Seemingly innocuous behaviors, such as sleeping with a lamp glowing or television playing, can put you at increased risk for cancer. That's because light exposure at night short circuits melatonin production and could prompt abnormal cell growth [source: Fox].