| Abstract: | The biologic effects of a purified long-acting porcine calcitonin (pTCT) were investigated in 45 children without any known renal, skeletal, endocrine, or metabolic disorder. pTCT was given as a single im injection at dose levels varying from 1 to 150 MRC u/1.73 m2. Administration of the highest dose was followed by a decrease in serum calcium and phosphorus concentrations and in tubular reabsorption of phosphorus, serum calcium and phosphorus concentrations and in tubular reabsorption of phosphorus. Mean maximal variation of serum calcium was -- 13.8 +/- 2.1 mg/l in children less than 3 years old, versus -- 8.2 +/- 0.9 mg/l (p less than 0.01) in older ones. Such an age-related differences was not observed for the hypophosphatemic action of pTCT. In 40 subjects aged 3 to 14 years the threshold for pTCT hypocalcemic activity was between 1 and 5 MRC u/1.73 m2. No significant differences in the effects on serum calcium of either 10, 25, 75 or 150 MRC u/1.73(2) m could be found. The threshold for pTCT hypophosphatemic activity was between 10 and 25 MRC u/1.73 m2 with, similary, no dose-response relationship for doses varying from 25 to 150 MRC u/1.73 m2. The present data demonstrate the high sensitivity of children, especially those younger than 3 years, to pTCT; furthermore, the lack of a dose-response relationship indicates that the pharmacological use of pTCT in pediatrics at doses higher than 10 to 25 MRC u/1.73 m2 is unnecessary. |
