Serum relaxin in patients with hydatidiform mole.

Human chorionic gonadotropin (hCG) is considered to be one of the factors that regulates relaxin secretion in humans. However, the secretory pattern of relaxin has not been evaluated in pregnancy complicated by hydatidiform mole, where circulating hCG levels are higher than in normal pregnancy. In the present study, relaxin, progesterone, and hCG levels were determined by radioimmunoassay in patients with hydatidiform mole before and after evacuation of the mole. Serum immunoreactive relaxin and progesterone levels in patients with hydatidiform mole were similar to those in normal women at corresponding weeks of pregnancy before evacuation of the mole, though hCG levels were significantly higher. The fall of relaxin levels after evacuation of the mole was slower than that of hCG or progesterone. This finding may reflect a continued stimulation of the corpus luteum by lower, but still effective, hCG levels persisting after evacuation of the mole. An extraluteal source of relaxin cannot be excluded.