Transcortin

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Serpin peptidase inhibitor, clade A (alpha-1 antiproteinase, antitrypsin), member 6, also Corticosteroid-Binding Globulin or Transcortin
Identifiers
Symbol(s)	SERPINA6 CBG
Entrez	866
OMIM	122500
RefSeq	NM_001750
UniProt	P08185
Other data
Locus	Chr. 14 q32.1

Transcortin, also corticosteroid-binding globulin or CBG, is officially called serpin peptidase inhibitor, clade A (alpha-1 antiproteinase, antitrypsin), member 6. It represents an alpha-globulin that has high affinity for binding cortisol. The Cortisol is thought to be biologically active only when it is not bound to transcortin. Approximately 75% of the cortisol in circulation is bound to this plasma protein. In addition, 60% of aldosterone in blood is bound to this plasma protein as well. Transcortin also binds progesterone.

Transcortin is produced by the liver and is regulated by estrogens. Therefore, plasma transcortin levels increase during pregnancy, and are decreased in cirrhosis.