M.J.
I am 42 and the same thing started happening to me. I started taking hair vitamins from GNC called NourishHair and also started using this shampoo called NuGro. The shampoo really has made a difference and my hair has filled back in where it started thinning around the temples. Check out their website http://www.nugrohairproducts.com and give them a try.
Hope this helps,
M.