Test Summary

Pancreastatin (PST), also called chromogranin A amide, is a 49-amino acid peptide that was first isolated from porcine pancreas. Pancreastatin is one of a number of biologically active peptides produced by proteolysis of the precursor molecule chromogranin A (CGA). It was first described as an inhibitor of insulin secretion, but since then many different effects have been reported. Pancreastatin is functional in humans in vivo, affecting both carbohydrate and lipid metabolism. Indeed, its actions are potent and specific. Pancreastatin is cleaved from CHGA in hormone storage granules in vivo, and its plasma concentration varies in human disease. The pancreastatin region of CHGA gives rise to three naturally occurring human variants, one of which (Gly297Ser) occurs in the functionally important carboxyl terminus of the peptide and substantially increases the peptide s potency to inhibit cellular glucose uptake. These observations establish a role for pancreastatin in human intermediary metabolism and disease and suggest that qualitative hereditary alterations in pancreastatin's primary structure may give rise to individual differences in glucose disposition. Historically analysis of pancreastatin levels has been utilized as a biomarker to establish diagnosis, and in prediction of disease recurrence, potential outcome, and efficacy of therapy in neuroendocrine tumors (NETs). However, there is growing literature on the limitations of use of monoanalytes, such as PST & Chromogranin A, for NET assessment, although conversely Chromogranin A and derived peptides are still perceived as most valuable markers of NETs. Concurrently there is increasing body of evidence on the importance of bioactive peptide fragments of Chromogranin A, including PST, in a spectrum of regulatory activities, important to maintaining homeostasis, involving the endocrine, immune, and cardiovascular systems. Hence the use of PST testing, and knowledge on the clinical implications is actively evolving towards a broader testing population.

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