Several good suggestions in this post - http://www.medhelp.org/posts/ADD---ADHD/my-3-year-old-son/show/1439476
Also check out the child behavior forum. Just scroll through and look for posts about "out of control 4 year olds" . You will find plenty of posts and good ideas.
If you really want to follow up on the ADHD, you will probably have better luck with a pediatric psychiatrist then a pediatrician.
Finally, Its probably a good idea to start reading up on ADHD. I always recommend the book, "The ADD/ ADHD Answer book," by Susan Ashley. Its hard to find websites that deal with kids so young. This one has some good ideas. http://www.ncpamd.com/PracticalHintsADHD.htm
And, of course, the possibility always exists that he is just the typical, out-of-control 4 year old. If so you might want to check out the book, "SOS Help for Parents," by Lynn Clark. Basically, it shows how to effectively change your childs behavior through using timeouts, etc.
Hope some of this helps. Good luck!