Familial hypocalciuric hypercalcemia is a genetic disorder causing high calcium levels due to a mutation in the calcium-sensing receptor gene. It may be asymptomatic and requires differentiation from primary hyperparathyroidism through genetic and urine tests. Treatment varies depending on the condition.
Familial hypocalciuric hypercalcemia is a genetic disorder that causes high levels of calcium due to a mutation in the calcium-sensing receptor gene. In most cases the condition can be completely asymptomatic and go undetected for life, requiring no treatment. Familial hypocalciuric hypercalcemia is also sometimes referred to as benign familial hypercalcemia and may require genetic or other testing to differentiate it from primary hyperparathyroidism, which more commonly causes high calcium levels.
Due to the mutation in the calcium sensitive receptor gene in patients with familial hypocalciuric hypercalcemia, the body thinks that the calcium levels are low and blood calcium increases. This is referred to as hypercalcemia. Normally, if blood calcium levels increase, urinary calcium production also increases, but in the case of familial hypocalciuric hypercalcemia this is not the case and urinary calcium levels tend to be low, which is called hypocalciuria.
The parathyroid gland is a major player in sensitive feedback mechanisms involved in the body’s calcium balance, and in the case of primary hyperparathyroidism, parathyroid hormone levels tend to be elevated. In familial hypocalciuric hypercalcemia, however, parathyroid hormone levels may be slightly increased, or at normal levels. Differentiation between primary hyperparathyroidism and familial hypocalciuric hypercalcaemia will be made using a variety of tests which may include genetic testing and a 24-hour urine calcium test.
A 24-hour calcium urine test is done by collecting urine over 24 hours. Usually the recommended process is for the first urination of the morning to be done in the toilet and all subsequent urine to be collected in the appropriate collection container obtained from the laboratory. This is continued until the next morning when the first urine is also collected in the bottle. The amount of calcium is then measured, and low or high levels of calcium excretion in the urine can be determined.
Genetic testing is done by PCR and DNA sequencing on a blood sample. The results of this test can only be obtained from the laboratory after 14-21 days. Diagnosing familial hypocalciuric hypercalcemia and differentiating between other conditions that can cause high calcium levels are important to ensure proper treatment. If you have primary hyperparathyroidism, you may need a parathyroidectomy or removal of the gland. In patients with familial hypocalciuric hypercalcaemia, this is not usually recommended.
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