Determination of Urinary cAMP in the Patients with Urinary Stones

Kim, Kun Do; Chai, Soo Eung

Abstract

Among many causes of calcium containing urinary stones, the hypercalciuria associated with normocalcemia is the most common one. Absorptive hypercalciuria and renal hypercalciuria constitute two major forms of idiopathic hypercalciuria. According to Coe et al., a renal leak of calcium and secondary hyperparathyroidism are present in renal hypercalciuria but not in absorptive hypercalciuria. It has been suggested that fasting urinary cAMP may provide a measure of parathyroid function. So determination of fasting urinary calcium and cAMP may be useful in the differentiation of the two major forms of idiopathic hypercalciuria. We performed the study to evaluate the significance of urinary calcium and cAMP in the determinating the types of hypercalciuria. Calcium metabolism studies and urinary cAMP determination were done in 28 in-patients with urinary stones under usual diet and fasting state. The results were as followings: 1. Among 28 patients, 15 patients had renal hypercalciuria, 6 had absorptive hypercalciuria and 7 had normocalciuria. 2. On usual diet, 24-hour urine cAMP level was 3.815+/-0.560 nmol/mg creatinine in renal hypercalciuria, 3.508+/-1.253 nmol/mg creatinine in absorptive hypercalciuria and 3.202+/-0.980 nmol/mg creatinine in normocalciuric patients. 3. On fasting state, 2-hour urine cAMP level was 4.611+/-2.591 nmol/mg creatinine in renal hypercalciuria, 4.304+/-3.173 nmol/mg creatinine in absorptive hypercalciuria and 2.400+/-1.080 nmol/mg creatinine in normocalciuric patients. 4. urinary cAMP on usual diet and fasting condition did not differ significantly among 15 renal and 6 absorptive hypercalciuric patients. (t-value; 0.82 and 0.22, respectively, p>0.1)