By the way, doctor: Why did my doctor prescribe steroids?

Q. I have been diagnosed with temporal arteritis and am being treated with a drug called prednisone, which the doctor says is a steroid. I know athletes use steroids to bulk up, and I can't see how that would have anything to do with temporal arteritis. Can you explain?

A. I understand your confusion.

The word steroid encompasses a large group of chemicals, each of which has very different effects on the body. Plants and animals contain hundreds of different kinds of steroids. Cholesterol, estrogen, testosterone — they're all steroids. Every steroid has a basic chemical structure that contains four rings of carbon atoms, but there are many variations beyond those four basic rings. Different steroids can have very different effects on the body because of those variations.