A 24-year-old woman with a molar pregnancy has serum beta-hCG measured serially. The beta subunit of hCG is structurally unique compared with the other glycoprotein hormones because it:
- A shares its alpha subunit with LH, FSH and TSH while conferring biological specificity through its own beta chain ✓
- B is composed of a single polypeptide chain without carbohydrate moieties
- C is synthesised entirely by the maternal pituitary rather than the placenta
- D contains an identical beta chain to TSH, allowing cross-reactivity in all assays
Correct answer: A. shares its alpha subunit with LH, FSH and TSH while conferring biological specificity through its own beta chain
Explanation
hCG belongs to the glycoprotein hormone family along with LH, FSH and TSH. All four share a common alpha subunit; hormonal specificity resides in the beta subunit, which is why assays target the beta chain of hCG. The molecule is heavily glycosylated and placental in origin, eliminating options B and C. Its beta chain differs from that of TSH, killing option D.
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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