Acid-labile subunit (ALS) deficiency is characterized by severe reduction of IGF-I and IGFBP-3 that remain low after GH treatment, associated with mild growth retardation. ALS, encoded by the IGFALS gene, is mainly produced by the liver. The patients were found to be carriers for IGFALS gene mutations. ALS protein is a key component of the circulating IGF ternary complex. The main role of ALS is the extension of IGF-I half life by protecting it from degradation and preventing the passage of IGF-I to the extravascular compartment.
