Human chorionic gonadotropin is the hormone produced early in pregnancy that keeps the corpus luteum producing progesterone; it may be injected to stimulate ovulation and progesterone production. This hormone is also elevated in trophoblastic disease and germ cell cancers and thus serves as a useful tumor marker for these cancers. Patients with non-cancerous conditons such as inflammatory bowel disease, duodenal ulcers, or cirrhosis or cancers of the breast, lung, pancreas, ovary, or gastrointestinal system may have elevated HCG levels.