Stimulation of calcitonin secretion by an oral calcium load test in normal subjects and in idiopathic renal stone formers.

Circulating concentrations of calcitonin (CT) have been found high in idiopathic renal calcium stone formers (RSF). It has been postulated that this could result from increased serum calcium concentrations following calcium-containing meals. To verify this hypothesis, 15 male idiopathic RSF and 15 male normal subjects underwent plasma CT measurements, following an extraction-concentration technique (exCT), in basal state and during an oral calcium load test. Most RSF exhibited increased excretion of calcium following oral calcium loading, suggesting overabsorption of calcium, but serum calcium did not increase more in RSF than in normal subjects. Basal plasma exCT concentrations were normal in RSF. ExCT plasma concentrations following calcium loading, and the area under the curve of exCT levels, tended to be higher in RSF than in normal subjects, but not significantly. Our results thus do not support the hypothesis that increased plasma CT levels in RSF result from increased serum calcium concentrations following calcium-containing meals.