INCREASED INVITRO THYROTROPIC ACTIVITY OF PARTIALLY SIALATED HUMAN CHORIONIC-GONADOTROPIN EXTRACTED FROM HYDATIDIFORM MOLES OF PATIENTS WITH HYPERTHYROIDISM

The intrinsic thyrotropic activity of hCG purified from normal pregnan cy urine has been demonstrated in several laboratories. hCG has a spec ific thyrotropic potency of about 0.04-0.5 muU bovine (b) TSH/IU hCG, depending on the bioassay system. The corresponding potency for hCG de rived from pathological sources, such as hydatidiform moles and chorio carcinoma tissue, or from the serum of these patients has not been stu died as extensively. Since the biological activity of glycoproteins ca n be strongly influenced by variations in the oligosaccharide side-cha in composition, we have investigated the effect of anion exchange chro matography on the thyrotropic potency of hCG derived from the hydatidi form mole and serum of three hyperthyroid patients with molar pregnanc y. The activity for the fraction of total molar hCG immunoreactivity t hat was not retained by an anion exchange column (0.18-0.90 muU bTSH/I U hCG) was about twice that of the corresponding serum and molar hCG f raction eluting during the NaCl gradient elution (0.08-0.40 muU bTSH/I U hCG). The unretained hCG fraction corresponds to a previously descri bed hCG precursor that is partially desialated in the C-terminal regio n of the beta-subunit.