Progesterone increases serum CA-125 in endometriosis.

Serum level of CA-125 was monitored up to 48 hours after injection of 125 mg P-in-oil into patients with or without endometriosis in the follicular phase of their menstrual cycle. Circulating CA-125 levels remained unchanged at around 5 U/ml during the observation period in patients without endometriosis; however, a significant elevation was observed at 30 hours after injection in those patients with endometriosis (from 19.6 U/ml before injection to 30.0 U/ml at 30 hours after injection, P less than 0.05).