β-thromboglobulin β-thromboglobulin β-thromboglobulin (β-tg), or beta-thromboglobulin, is a chemokine protein secreted by platelets. it is a type of chemokine (c-x-c motif) ligand 7. along with platelet factor 4 (pf4), β-tg is one of the best-characterized platelet-specific proteins. β-tg and pf4 are stored in platelet alpha granules and are released during platelet activation. as a result, they are useful markers of platelet activation. β-tg also has multiple biological activities, for instance being involved in maturation of megakaryocytes. biological actions β-tg is a chemoattractant, strongly for fibroblasts and weakly for neutrophils. it is a stimulator of mitogenesis, extracellular matrix synthesis, glucose metabolism, and plasminogen activator synthesis in human fibroblasts. β-tg also affects megakaryocyte maturation, and thus helps in regulating platelet production. clinical uses levels of β-tg is used to index platelet activation. it is measured by elisa in blood plasma or urine, and often in conjunction with pf4. influences β-tg levels may increase with age. it is elevated in diabetes mellitus. β-tg levels have been found to be increased by treatment with the synthetic estrogen ethinylestradiol, though were not significantly increased by the natural estrogen estradiol valerate. levels of β-tg have also been found to be increased or unchanged during normal pregnancy.