Episodic secretion of human chorionic gonadotropin in early pregnancy.

The serum concentration of human chorionic gonadotropin (hCG) was measured at 10- to 60-minute intervals for 4-24 hours in 5 women at 5-8 weeks of pregnancy. hCG was found to be secreted episodically with pulses observed every 2-4 hours. The episodic secretion of hCG may have important implications to our understanding of both normal and abnormal reproduction.