Familial hypocalciuric hypercalcaemia

Familial hypocalciuric hypercalcemia
Classification and external resources
Specialty	endocrinology
ICD-10	E83.5
OMIM	145980 145981 600740
DiseasesDB	1326
MeSH	D006934
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Familial hypocalciuric hypercalcemia (FHH) is a condition that can cause hypercalcemia, a serum calcium level typically above 10.2 mg/dL. It is also known as familial benign hypocalciuric hypercalcemia (FBHH) where there is usually a family history of hypercalcemia which is mild, a urine calcium to creatinine ratio <0.01, and urine calcium <200 mg/day.

Most cases of familial hypocalciuric hypercalcemia are asymptomatic.

Types include:

Most cases of FHH are associated with loss of function mutations in the calcium-sensing receptor (CaSR) gene, expressed in parathyroid and kidney tissue. The perceived lack of calcium levels by the parathyroid leads to constitutively high levels of parathyroid hormone and therefore hypercalcemia. Functionally, parathyroid hormone (PTH) increases calcium resorption from the bone and increases phosphate excretion from the kidney which increases serum calcium and decreases serum phosphate.

Another form has been associated with chromosome 3q.

This condition is indicated by the presence of hypercalcemia (elevated levels of calcium in the blood) at the same time with hypocalciuria (low levels of calcium in the urine). (Usually elevated calcium levels in the blood are correlated with elevated calcium urine levels, as a properly sensing kidney works to excrete the mineral.) A family history could reinforce the diagnosis.

No treatment is generally required, as bone demineralisation and kidney stones are relatively uncommon in the condition.

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