A study of the properties of human chorionic gonadotropin (hCG) from total hydatidiform mole with low hCG immunoactivity

A study was conducted to define biochemical characteristics of human chorionic gonadotropin (hCG) in total hydatidiform mole patients with low serum and urinary hCG levels and to inquire into the reason for its low immunological hCG level by comparing with the hCG of molar patients with a high hCG level. Both hCGs purified from chorionic tissue of molar patients with low and high hCG levels have essentially identical physicochemical, immunological and biological properties. They have low levels of biological activity and practically identical amino acid and carbohydrate compositions. It appears that moles of patients with high levels as well as those with low levels of immunoreactivity produce this purified form of hCG. Extracts of molar tissue from patients with high levels of hCG immunoreactivity also contained other substances with apparent immunoreactivity which can be found in small amounts in tissue extracts from patients who excreted low levels of hCG immunoreactivity. In contrast, extracts of molar tissue and urine from patients with low hCG levels contained hCG-like substances which cannot be detected with the ordinary commercial hCG immunoassay kits. These differences may account for the different levels excreted by these two types of patients.