Urinary excretion of adenosine 3'5' monophosphate in vitamin D deficiency.

Urinary cyclic adenosine 3'5' monophosphate (AMP) excretion has been determined by radioimmunoassay in children with rickets and in control children. Cyclic AMP was greatly increased in children with rickets. The excretion of cyclic AMP correlated significantly with parathyroid hormone levels (PTH) and alkaline phosphatase, but not with age, calcaemia and serum inorganic phosphate. Calcium infusion led to a decrease in the excretion of cyclic AMP. The data are consistent with following hypothesis. During vitamin D deficiency, high PTH levels can increase the renal excretion of cyclic AMP. The effects of PTH on bone resorption fail to maintain the levels of serum calcium due to the lack of vitamin D. The mechanism by which the secondary hyperparathyroidism develops during vitamin D deficiency remains to be investigated.