In the past few issues of Second Opinion, you've read about many of the important effects of melatonin. Many people still think of melatonin as simply a sleep aid. But as you now know, there's so much more to this incredible hormone. And if you have Irritable Bowel Syndrome (IBS), or know someone who does, you'll be amazed at what it can do for your digestive tract.

If you have diabetes, you probably know that you're at risk of kidney failure. In fact, diabetes is responsible for 44% of kidney failure cases in the U.S., according to the National Institutes of Health. Researchers have recently found an important link between a vitamin deficiency and kidney disease. And the good news is there may be something you can do about it.

In the past, I've written quite a bit about testosterone replacement therapy (TRT). In June, I wrote about the position the American Association of Clinical Endocrinologists was taking on TRT: "The benefits to treat low testosterone in both men and women substantially outweigh any risks." I agree with their position, so much so that I take testosterone myself, and I regularly prescribe it to my patients, who have seen great results. So I was happy — but not surprised — to hear about a large new study confirming the benefits of TRT for men with low levels.