Primary Acid-Labile Subunit Deficiency due to Recessive IGFALS Mutations Results in Postnatal Growth Deficit Associated with Low Circulating Insulin Growth Factor (IGF)-I, IGF Binding Protein-3 Levels, and Hyperinsulinemia

Context: Up to 90% of circulating IGF-I and IGF-II are carried bound to either IGF binding protein (IGFBP)-3 or IGFBP-5 and the acid-labile subunit (ALS) in the form of tertiary complexes that extend their circulating half-life. Three cases of complete ALS deficiency have been recently reported in short-stature patients with very low circulating IGF-I and IGFBP-3 levels who presented with homozygous or compound heterozygous mutations in the ALS encoding gene (IGFALS; 16p13.3), thus supporting a role for ALS in the regulation of the bioavailability of IGFs during postnatal growth. Objective: We present the molecular and clinical characterization of two novel IGFALS mutations that caused complete ALS deficiency in three unrelated patients with postnatal growth deficit, low IGF-I and IGFBP-3 levels, and no GH deficiency. Results: IGFALS mutation screening identified a novel homozygous IGFALS missense mutation, which altered a conserved residue, N276S, in two of the probands. The third proband presented a nov...