Below is an instruction from Human. Write a response.
    ### Instruction:
    What are the genetic changes related to isolated growth hormone deficiency ?
    ### Response:
    Isolated growth hormone deficiency is caused by mutations in one of at least three genes. Isolated growth hormone deficiency types IA and II are caused by mutations in the GH1 gene. Type IB is caused by mutations in either the GH1 or GHRHR gene. Type III is caused by mutations in the BTK gene.
    