Your Endo is right!

Your son need more Hydrocortisone during fever.

37 to 37,5 centigrade (98.6 to 99.5 fahrenheit) is normal - depending where you measure the temperature

38 centigrade (100.5 fahrenheit)  is elevated temperture => you should double the daily HC dose

and at 38,5 centigrade (101,3 fahrenheit) you should triple the HC

 

regards Harald