One of the most primary functions of PTH is to inhibit the transport of water, bicarbonate ions and sodium into the proximal convoluted tubule by the synthesis of cAMP. This rule of thumb shows direct relationship between PTH and cAMP. In Primary Hyperparathyroidism, the synthesis of PTH in parathyroid gland increases exceptionally. Since PTH targets the renal tubules mainly therefore in primary hyperparathyroidism more PTH targets the renal tubules. This results in more production of cAMP. This happens because the nucleotide in cAMP synthesizes at extraordinary rate. More nucleotide means more cAMP which means more cAMP in the urine. This proves that PTH is the prime marker of cAMP level in urine.