CGB8 encodes one of the beta subunits of human chorionic gonadotropin (hCG), a critical hormone for pregnancy maintenance and early development 1. CGB8 is part of a gene cluster on chromosome 19.3 that includes six hCG beta-subunit genes (CGB3, CGB5, CGB6, CGB7, CGB8, CGB9), with CGB8, CGB5, and CGB3 encoding identical proteins that differ from the CGB7 variant 2. The protein functions by dimerizing with the hCG alpha subunit to form active hCG hormone 3. CGB8 shows distinct expression patterns, being highly expressed in trophoblastic tissues during pregnancy and at lower levels in non-placental tissues including testis, prostate, and lung 4. Disease relevance includes associations with recurrent miscarriage, where certain CGB8 genetic variants may modulate risk, though most studies show no significant association with pregnancy loss 56. Additionally, CGB8 expression is elevated in various cancers including breast tumors, where it may function independently of the LH/CG receptor pathway 7, and has been incorporated into prognostic models for oral cancer 8. Functional studies demonstrate that CGB8 maintains biological activity similar to other CGB variants in activating ERK1/2 signaling pathways 2.