Some tests to study the dynamic secretion of calcium-regulating hormones in childhood are presented. A low-calcium diet (less than or equal to 2 mg/kg/daily) for 1,25-dihydroxyvitamin D [1.25-(OH)-2D], ASU-eel-CT i.m. injection (80 U MRC/1.73 mq) for parathyroid hormone (PTH), and calcium infusion (2 mg/kg in 5') for calcitonin (CT) are employed. A significant increase in 1,25-(OH)-2D level (1 degree day: 47.0 +/- 6.7 pg/ml; 3 degree day: 73.2 +/- 6.9 pg/ml; p less than 0.001; n = 19), intact PTH values (basal: 29.7 +/- 7.5 pg/ml; +120': 68.2 +/- 7.8 pg/ml; p less than 0.001; n = 10) and monomeric CT concentrations (basal: 5.2 +/- 2.3 pg/ml; +10': 26.2 +/- 4.4 pg/ml; p less than 0.001; n = 18) have been observed. The employed tests are able to show a significant increase in calcium-regulating hormones in healthy children. These tests are a simple and reliable method without side-effects that may provide further information on the pathogenesis of some pediatric diseases with altered mineral homeostasis.