To test whether probabilistic Nnat+/-p overgrowth is driven by β-cell hyperplasia and resulting hyperinsulinemia, we artificially ‘clamped’ in vivo insulin levels at equal levels across groups by injecting animals with a single high-dose injection of streptozocin (STZ) to deplete the endogenous β-cell pool44 and implanting slow-release subcutaneous insulin pellets to restore insulin sufficiency equally across animals (Fig. 2e). The gene discussed is INS; the disease is hyperinsulinism.