A notable example is diabetes mellitus, which is caused by insufficient insulin production or insensitivity of tissues to insulin.2 Other examples are Laron syndrome, a growth delay linked to insufficient serum level of insulin-like-growth factor 1 (IGF1),50 and neurodegenerative diseases accompanied by a deficiency in nerve growth factors.6 Treatment of such diseases involves replacement of RTK ligands. This evidence concerns the gene INS and Laron syndrome.