Description
Cyclic adenosin-3′,5′-monophosphate (cAMP) serves as a second messenger in signal transduction of various hormones, such as adrenaline, ACTH, LH, FSH, glucagon and calcitonin.
The hormone itself is the first messenger, binding to specific membrane receptors of hormone-responsive cells. This leads to the activation of an enzyme located at the inner side of the cell membrane, called adenylate cyclase, which catalyses the synthesis of cAMP from ATP. The increased cellular level of cAMP initiates the activation of protein kinases. The determination of cAMP in urine or plasma has become increasingly more important in the clinical assessment of parathyroid functions. The parathyroid hormone (PTH) stimulates the synthesis of cAMP in the renal cortex and an increased secretion of cAMP. The nephrogenic cAMP is a specific marker of circulating PTH: 90 % of patients with hyperparathyroidism show increased levels of nephrogenic cAMP. The determination of nephrogenic cAMP is also significant for the differential diagnosis of hypercalcemia. Urinary levels of cAMP help aid in the diagnosis of hypoparathyroidism and pseudohypoparathyroidism.
