Serum calcitonin and blood mineral interrelationships in normal children aged six to twelve years.

Simultaneous measurements of serum immunoreactive thyrocalcitonin (iTCT), immunoreactive parathyroid hormone (iPTH), calcium, inorganic phosphate, magnesium, and alkaline phosphatase were made in 37 normal children whose ages ranged from 6-12 years. Between the ages of 6 and 12 there is a statistically significant rise in serum iTCT levels (r = 0.4638; P less than 0.01), and a fall in serum iPTH levels (r = 0.4976; P less than 0.01). There is a highly significant inverse correlation between serum iTCT and iPTH levels (r = 0.5248; P less than 0.005). Serum iTCT levels were inversely correlated with phosphate levels (r = 0.4989; P less than 0.01), the latter being age dependent and falling significantly between the ages of 6 and 12 (r = 0.4802; P less than 0.001). There was no significant relationship between serum calcium levels and iTCT, iPTH, or age. Serum magnesium levels were not correlated with calcium, iTCT, or iPTH levels.