CgA

Clinical significance
Chromogranin A is a protein that, like catecholamines, is secreted by the cells of the adrenal medulla and the sympathetic nervous system.
Chromogranin is mainly used for post-operative surveillance for recurrence of phaeochromocytoma; it is also often used for diagnosis, where a high value combined with high catecholamine levels and a normal eGFR has a very high positive predictive value (when eGFR is below normal, insufficient elimination of chromogranin causes a falsely high level in the plasma).
It should be remembered, however, that high chromogranin levels can also be found in medullary thyroid cancer, small cell lung cancer and epithelial cancers with neuroendocrine differentiation (prostate, breast, ovary, pancreas, colon).