I do not have CAH (am just a carrier) but I do experience severe migraines several times a month.  A couple of things you might want to ask your son are:  during the headache is he sensitive to light, sound, or smells?  These are common during migraines.  Is the pain on one side of his head?  As far as things that help to ease the pain and make the migraine go away, there are several tricks I have learned over the years that seem to help me.  The best one is an ice pack at the base of my head right where it meets my neck.  Is there anyone else in your family who has a history of migraines?  There is research being conducted that is showing a possible genetic link (not substantiated as of yet).  Also, my migraines started right around puberty (about age 8, I started puberty early) but my twin brother’s started right around age 12.  Something you could do to help your endo when discussing this particular situation is have him keep a "headache journal".  Basically, just have him write down the foods he eats and activities going on during the days that he gets the headaches.  If they are migraines, they probably have a trigger.  If he learns his triggers, most of the headaches can be avoided.  For example, my triggers are change in sleep pattern, hormones and stress.  If I stay up too late or get more than 9 hours sleep, I always get a migraine.  I also get them right around menstruation and if I am really stressed at work.  Hope all goes well and I hope this information helps.

Robin