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Human chorionic gonadotropin （HCG） is a glycoprotein hormone consisting of two noncovalently bonded subunits, alpha and beta [PMID: 68892], and is normally synthesized by placental trophoblasts during pregnancy. The alpha subunit of hCG is identical to the alpha subunit of 3 hormones synthesized by the anterior pituitary gland but the beta subunit of each of these hormones is unique and confers biological specificity. Among the beta subunits, hCGbeta and Lhbeta are vey homologous such that both hormones bind to the LH receptor.