Laura,

I think that doctor was simply not familiar with CAH and was erring on the side of caution.

For those who are interested in this sort of thing (ChrisD, Carol?) there is a website:  http://www.anaesthetist.com/physiol/basics/metabol/cyp/cyp.htm  that explains the basis of drug interactions and how adverse interactions can be predicted and therefore avoided. The Drugs and CYP - Table located about two thirds down the page lets you click on a drug to see what enzyme(s) affect the drug or are affected by it. Further down the page you can click on that enzyme to see what other drugs interact with the enzyme and the nature of the interaction.

According to the information available from the above website, hydrocortisone has no known adverse (or benign) drug interactions.