FHH is a very rare genetic problem with high blood calcium and low urine calcium. If you have never heard of FHH, then do not read this page. This is for people who were told they have FHH because their 24-hour urine calcium is low--% chance you do not have FHH. Secondary Hyperparathyroidism occurs when the parathyroid glands become overactive because of something else . Kidney failure is almost always the cause. Secondary hyperparathyroidism is never associated with high blood calcium.