Urinary Cyclic AMP

Influence of calcium infusion on urinary cyclic AMP and phosphate in hyperparathyroidism

Urinary cyclic AMP (cAMP) and phosphate were measured before and after calcium infusion in 12 patients with operatively verified primary hyperparathyroidism (PHP) and in 12 healthy persons. In normal subjects infusion of calcium caused a reduction in urinary cAMP directly correlated to the preinfusion values and inversely correlated to the serum calcium concentration determined as albumin-corrected serum calcium. In normal subjects with high normal albumin-corrected serum calcium the infusion of calcium caused no or only a small depression in the urinary excretion of cAMP. Changes in phosphate excretion were not correlated to the calcium concentration. Four of the 12 hyperparathyroid patients showed normal relative suppression in urinary cAMP after the infusion of calcium, and 5 had normal suppression of phosphate excretion. It is concluded that some patients with PHP retain calcium-sensitive secretion of PTH, and that the classical calcium infusion test is of doubtful value in the diagnosis of PHP.

The pathogenesis of idiopathic hypercalciuria: an alternative hypothesis

Currently, four hypotheses attempt to explain the pathogenesis of idiopathic hypercalciuria. Proposed theories include hypersecretion of parathyroid hormone, hyperabsorption of calcium by the gastrointestinal tract, hyperreabsorption of calcium by the kidney, and hyperexcretion of phosphate by the kidney. These hypotheses are more descriptive than explanatory. A new hypothesis is suggested which encompasses the divergent findings. Idiopathic hypercalciuria may result from hypersecretion of parathyroid hormone which is active at the gastrointestinal and bone target site but is partially defective at its renal site of action.

Levels of adenosine 3',5' cyclic monophosphate and guanosine 3',5' cyclic monophosphate in single urine specimens collected from a large population of healthy subjects

The levels of adenosine 3',5' cyclic monophosphate and guanosine 3',5' cyclic monophosphate have been measured in random urine specimens provided by 95 healthy volunteers with a view to assessing the importance of the effects of certain physiological factors on the cyclic nucleotide levels in this type of specimen, and to establish suitable reference ranges for future patient monitoring studies. Of the factors investigated, only the stage of the menstrual cycle was found to have a significant effect; even this variation was still within the overall normal reference range. Measurements of urine cyclic nucleotides were also made in relation to the method of specimen collection, handling, and storage. From these studies it was concluded that if the specimen is placed in a refrigerator within a few hours of collection and then transferred to a deep-freeze within 48 hours, these factors do not present any major problems for the subsequent assay of the cyclic nucleotides.