My 15 month old son is bang on the average levels for his age (nearly 2 stone in weight now), using hydrocortisone tablets for maintenance. We do 6 monthly heel prick tests to check his blood levels 4 times a day over 2 days. He'll get his first x-ray for bone age in July. I would get a second opinion if you're not happy - it's not worth the risk of it not being maintained properly.