A STUDY OF HYPERCALCIURIA IN CALCIUM-CONTAINING UROLITHIASIS

Abstract

Calcium metabolism of normal Japanese adults and patients with calcium-containing urolithiasis with or without hypercalciuria was investigated by fasting and calcium load test.
1) The means±SD of urinary calcium (Ca) and cyclic AMP (c-AMP) excretion from 15 normal subjects were as follows:
Fasting urinary Ca excretion=8.04±6.0mg/100ml GF×100
Loading urinary Ca excretion=19.02±6.4 mg/100ml GF×100
Fasting urinary c-AMP excretion=3.28±1.44nmol/100ml GF
Loading urinary c-AMP excretion=2.20±0.88nmol/100ml GF
2) In 29 patients with normocalciuric urolithiasis, no significant difference in urinary calcium excretion was observed compared to the normal subjects.
3) Thirty-one hypercalciuric patients could be classified into 3 subtypes as follows: type 1 patients with normal urinary calcium and urinary c-AMP in fasting, and increased urinary Ca and normal c-AMP in Ca load; Type 2a patients with increased urinary Ca and increased c-AMP in fasting, and increased urinary Ca and normal c-AMP in Ca load; and type 2b patients with increased urinary Ca and normal c-AMP in fasting, and minimal increase in urinary Ca and normal c-AMP in Ca load.
Type 1 hypercalciuria appeared to be caused by intestinal hyperabsorption of Ca, and most of the younger male patients with calcium oxalate stones belonged to this group. Type 2a hypercalciuria seemed to be attributed to the renal leak of serum Ca due to a decrease of Ca reabsorption in the renal tubules. The majority of the patients with this type consisted of elderly women with calcium phosphate stones. Type 2b hypercalciuria appeared to be primarily caused ty bone resorption in elderly patients.
4) Oral Ca load in 8 patients with primary hyperparathyroidism showed no suppression of parathyroid function, but resulted in a significant increase of the serum Ca levels compared to the responses in the normal subjects and the hypercalciuric patients.