If you are finding that your knowledge surpasses what is available through most consumer health sites and books and you feel ready to tackle in-depth information written for health professionals, try searching some medical textbooks and journal articles.
PubMed is also available at PubMed.gov for those that are not affiliated with MSU.
Once you do your search, look over to the left hand side of the page. There you can choose to narrow down your results:
Alternatively, if you are not an MSU affiliate you may wish to use PubMed Central, a free full-text archive of biomedical and life sciences journal literature. PubMed Central works very similar to PubMed, but the full-text of results are all freely available and some of the options for filtering results are different.