SERUM URATE AND RENAL-FUNCTION IN DIFFERENT FORMS OF HYPERCALCEMIA

In order to investigate the relationships between serum calcium, urate and kidney function, serum calcium, urate, creatinine and urea were measured at 100 occasions in hypercalcemic cancer patients together with 113 preoperative measurements in HPT subjects and 106 measurements in normocalcemic control persons. When compared to normocalcemic control subjects (serum urate 336 +/- 110-mu-mol/l) both HPT subjects (356 +/- 98 mmol/l, p < 0.006) and the cancer patients (407 +/- 179 mmol/l, p < 0.001) showed raised levels of serum urate. While serum urate was correlated to serum creatinine in all groups (r = 0.40-0.59, p < 0.0001) a significant correlation to serum calcium was only seen in the HPT group (r = 0. 28, p < 0. 004). This relation persisted also after correcttion for age, sex and serum creatinine in the multiple regression analysis. Serum creatinine was similar in all groups but significantly correlated to serum calcium only in the HPT subjects (r = 0.29, p < 0.003). Serum urea was not significantly correlated to serum calcium in any of the groups but was elevated in the cancer group (8.3 +/- 4.4 vs 6.2 +/- 2.9-mu-mol/l in the control group, p < 0.0001). This elevation in serum urea seen in the cancer patients might rather be explained by dehydration or catabolism than an impaired kidney function. In conclusion, while serum urate is related to the kidney function both in normo- and hypercalcemia, it also seems to be related to the hypercalcemia in HPT subjects but not in cancer patients. In hypercalcemia associated with malignant disorders, other factors such as an increased turnover of cyclis nucleotides and dehydration may also contribute to the hyperuricemia.