Of note, prolonged IGFBP3/TMEM219 blockade with ecto-TMEM219 was associated with significant beta-cell expansion, which lead to a significant increase of both islet area and peripheral insulin levels (Fig. 5f, h, k and Supplementary Fig. 6k), mimicking nesidioblastosis. The gene discussed is IGFBP3; the disease is familial hyperinsulinism.