Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Sertoli cell-only syndrome ?
    ### Response:
    Sertoli cell-only syndrome (SCO syndrome) is a condition of the testes that causes infertility in males due to having only Sertoli cells (cells that nurture immature sperm) lining the seminiferous tubules (tubes inside the testicles where sperm develop). Men typically learn they are affected between ages 20-40 when being evaluated for infertility and are found to have no sperm production (azoospermia).
    