Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Familial isolated hyperparathyroidism ?
    ### Response:
    Familial isolated hyperparathyroidism (FIHP) is an inherited form of primary hyperparathyroidism that is not associated with other features. The age of diagnosis varies from childhood to adulthood. In FIHP, tumors involving the parathyroid glands cause the production and release of excess parathyroid hormone, which in turn causes increased calcium in the blood (hypercalcemia).
    