A step towards cinacalcet testing for the diagnosis of primary hyperparathyroidism: comparison with the standardized intravenous calcium loading. A pilot study

Summary Objective A calcium load to suppress parathyroid hormone ( PTH ) secretion can help to perform the diagnosis in some case of primary hyperparathyroidism ( PHPT ) with atypical presentation. A similar test with calcimimetic, which avoids hypercalcaemia, would be of interest. Our proof of concept study was conducted to compare firstly the results of a single‐dose cinacalcet testing with those of the standardized short‐time calcium load in healthy control ( HC ) and secondly the results of the single‐dose cinacalcet testing in HC and in PHPT . Methods Twelve HC s received in a random order, at a 2‐week interval, either 0·33 mmol/kg calcium gluconate intravenously for 3 h, or a single oral dose of 30 mg or 60 mg cinacalcet. Twelve PHPT s received 30 mg cinacalcet and twelve other PHPT s 60 mg cinacalcet orally. Calcaemia and serum PTH levels were measured basally and then hourly for 6 h. Results In HC , plasma calcium did not significantly change after cinacalcet intake, whereas calcaemia rose up to 3·47 ± 0·05 mmol/l (mean ±  SEM ) at the end of the calcium load. PTH dropped from basal level to a similar extend (≥80%) with 60 mg cinacalcet and calcium load, whereas the decrease was significantly lesser ( P  < 0·01) with 30 mg cinacalcet. In PHPT , serum PTH levels dropped by 44·8 ± 6·9% and 58·2 ± 5·3% 1 h after the respective intake of 30 and 60 mg cinacalcet. One hour after the oral intake of 60 mg cinacalcet, serum PTH levels were <8 ng/l in HC and ≥8 ng/l in PHPT . Conclusion Sixty milligrams of cinacalcet provides similar results as the standardized calcium load test; PHPT patients have a lower response to 60 mg cinacalcet than HC .