400 nmol?L is too high.  Don’t know how the thread went from here on out but I think it is too high.  Equivalent to around 12’000 ng/dl ATLEAST and suggests to me along with other symptoms you have mentioned that your son is under treated.  Tests taking months to be done?  Change your endo asap.  Sounds like he’s either clueless or cannot be bothered to explain things properly for you or his rationale around delaying tests for one.    Even if he "thought"  the boy was ok, he should be running blood tests asap and not putting them off or explaining to you why he won’t run any for a couple of months.  When was the last one done giving you the 400nmol/L result?  In response to that did he raise the doses or mention anything about the test results being awry or needing to retest again in say a month to check if things had changed.  I am not really sure what a boy of your sons age should have result wise where 17 OHP levels are concerned, but when Ashley had results a few years ago 26 nmol/L’s higher than that it was considered very high.