Endocrine Abstracts

Introduction: Hypoparathyroidism is most commonly observed following neck surgery and is characterized biochemically by deficient parathyroid hormone (PTH) and hypocalcaemia alongside hyperphosphataemia and reduced 1,25-dihydroxyvitamin D. Standard treatment with oral calcium and vitamin D aims to maintain serum calcium within the low-normal range whilst avoiding hypercalciuria due to over replacement. However, concerns remain over the presence of hypercalciuria and the associated risk of renal calcification.

Aim: To assess whether serum and urine biochemical parameters are associated with the presence of renal calcification in hypoparathyroid patients on Alfacalcidol therapy.

Method: A 12-month audit of the laboratory database was undertaken of paired requests for 24-h urine calcium (24 h-Ca), spot calcium:creatinine ratio (Ca:Creat), serum calcium, phosphate, urea, and creatinine. A review of case notes was performed to confirm aetiology of hypoparathyroidism, Alfacalcidol dose and results of renal ultrasound scan (USS).

Results: A total of 34 patients were identified as having hypoparathyroidism and receiving Alfacalcidol therapy. 24 h-Ca and Ca:Creat were not-normally distributed, however significant associations were found between 24 h-Ca and Ca:Creat when log-transformed (linear regression β-coefficient=0.64; 95% CI 0.36–0.92; P<0.001, β=0.63). 17 patients had documented hypercalciuria evidenced by elevated 24 h-Ca (five patients), Ca:Creat (eight patients), or both (four patients). 13 patients had undergone renal USS; four had evidence of renal calcification. Interestingly, these four patients each had an elevated Ca:Creat, in contrast with only one patient having elevated 24 h-Ca.No patient had hypercalcaemia. However, 20 patients had low, or low-normal serum adjusted calcium (Ca <2.2 mmol/l); nine of these patients having documented hypercalciuria evidenced by an elevated 24 h-Ca (78% of patients) or Ca:Creat (89% of patients).

Conclusion: Ca:Creat appears a sensible and convenient marker for the follow-up of patients on long term Alfacalcidol therapy to determine associated risk of renal calcification.