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Familial hypocalciuric hypercalcaemia: a study of four kindreds
G Toss1, H Arnqvist, L Larsson
1Department of Internal Medicine, University Hospital, Linköping, Sweden.
Insights
Familial hypocalciuric hypercalcaemia (FHH) is a hereditary condition identified in four Scandinavian kindreds. Early diagnosis through family screening is crucial for managing this typically benign disorder.
Area of Science:
- Endocrinology
- Genetics
- Metabolic Disorders
Background:
- Hereditary hypercalcaemia presents diagnostic challenges.
- Distinguishing FHH from primary hyperparathyroidism is essential for appropriate patient management.
Purpose of the Study:
- To investigate the prevalence and characteristics of hereditary hypercalcaemia in four Scandinavian kindreds.
- To assess the diagnostic utility of family screening in identifying familial hypocalciuric hypercalcaemia (FHH).
Main Methods:
- Clinical investigation of 72 subjects across four kindreds.
- Biochemical analysis including serum calcium, parathyroid hormone (PTH), and urinary calcium excretion.
- Comparison with an age-matched cohort of primary hyperparathyroidism patients.
Main Results:
- Thirty-seven subjects (51%) exhibited hypercalcaemia with autosomal dominant inheritance.
- Subnormal urinary calcium excretion (<2.5 mmol/day) was observed in 45% of hypercalcaemic patients.
- Parathyroid surgery in 12 subjects yielded no adenomas and inconsistent normalization of calcium levels.
Conclusions:
- The findings are consistent with familial hypocalciuric hypercalcaemia (FHH) in Scandinavia.
- Family screening is vital for diagnosing FHH and avoiding unnecessary parathyroid surgery.
- FHH should be considered in the differential diagnosis of hypercalcaemia due to its generally benign prognosis.
Abstract:
Four kindreds with hereditary hypercalcaemia have been investigated. Thirty-seven of 72 subjects examined had hypercalcaemia with an autosomal dominant pattern of inheritance. Hypercalcaemic patients had total serum calcium of 2.91 +/- 0.12 mmol l-1. Serum parathyroid hormone (PTH) was normal while daily urinary calcium excretion was subnormal (below 2.5 mmol) in 45%. Comparison with an age-matched group of patients with primary hyperparathyroidism gave a small overlap regarding serum human PTH, urinary calcium and the ratio between calcium clearance and creatinine clearance. Family screening therefore is of diagnostic importance. Twelve subjects had been subjected to parathyroid surgery before the correct diagnosis was settled, none of the cases had an adenoma. Three patients became normocalcaemic and the others had persistent hypercalcaemia. One male non-abuser had seven episodes of acute pancreatitis before surgery and none after. The findings in all four kindreds are compatible with familial hypocalciuric hypercalcaemia (FHH). This hereditary disorder of unknown aetiology, therefore, also exists in Scandinavia. It is of importance to consider FHH in the differential diagnosis of hypercalcaemia, since this disorder usually has a benign prognosis if untreated.