Familial hypocalciuric hypercalcemia: description of a new kindred with emphasis on its difference from primary hyperparathyroidism.

In order to better understand the difference between familial hypocalciuric hypercalcemia (FHH) and primary hyperparathyroidism (PHP), 4 adults with this disease (FHH(+], from the same kindred, and spanning 2 generations, were compared with 6 patients with PHP, 10 normal controls (N) and 3 unaffected members of the same kindred (FHH(-]. Clinically speaking, the FHH(+) patients were asymptomatic while those with PHP had recurring renal stones. Various phosphocalcic balance elements were measured in blood and urine, in a fasting state, following oral loading of 1 g calcium, as well as in 24-hour urine specimens. Serum calcium levels were slightly higher (11.90 +/- .14 vs 11.37 +/- .24 mg/dl; p less than .05), in patients with FHH(+), but serum phosphorus (2.47 +/- .38 vs 2.88 +/- .40 mg/dl), serum parathyroid hormone (301 +/- 147 vs 291 +/- 224 pg/ml) and serum 1,25(OH)2D (52.8 +/- 6.7 vs 55.0 +/- 12.0 pg/ml) values were similar to those observed in patients with PHP. Urinary calcium present in FHH(+), while fasting (.064 +/- .043 mg/100 ml G.F.), after the calcium loading (.150 +/- .071) and in the 24-hour specimen (.089 +/- .016), was below the 95% confidence limit of values obtained in patients with PHP (.225 +/- .026, p less than .001; .413 +/- .066, p less than .001; 314 +/- .080, p less than .001), but similar to those obtained in N and FHH(-).(ABSTRACT TRUNCATED AT 250 WORDS)