I have seen 2 newborns recently with hyperinsulinemic hypoglycemia. Both of them settled down with diazoxide.How common is the transient form?

we do see these cases, and usually they respond in a week or 10 days time.

difficult to say how common but its not very uncommon too.

We also come across infants that clearly have slightly elevated s-insulin (with low blood sugars) despite hypoglycemia.

My limited experience is - diazoxide has worked very well and we have been succesfully withdrawing diazoxide before discharge (like after a week or so).

 

We come across infants that have e hyperinsulinemic hypoglycemia, few are transit responded to diazoxide the rest turn to be Persistent hyperinsulinemic hypoglycemia of infancy (PHHI) they have Mutations of SUR1. and 2 cases with Donohue syndrome (severe insulin resistance, hyperinsulinemia postprandial hyperglycemia, preprandial-hypoglycemia. 

This is not common; in 5 years just saw 2 cases; effectively good response to diazoxide