Although ACAN deficiency has become increasingly recognized [5-11, 16-18], information on the effects of growth-promoting interventions have largely been limited to retrospective reviews [6, 7, 10, 16, 19] and/or patient cohorts that may have been treated with different GH regimens of varying duration, with or without puberty blockade [6, 7, 10, 16, 18-21], thus making it difficult to determine the efficacy of the treatment. The gene discussed is ACAN; the disease is hyperinsulinemic hypoglycemia, familial, 4.