Collagen metabolism in gynecologic patients: changes in the concentration of the aminoterminal propeptide of type III procollagen in serum. We have previously found the serum concentration of the aminoterminal propeptide of type III procollagen, an indicator of collagen metabolism, to be increased in advanced ovarian cancer. In this study we measured the serum aminoterminal propeptide of type III procollagen concentration in healthy women during the menstrual cycle and in patients with salpingo-oophoritis, leiomyomas, endometriosis, and benign ovarian tumors. The concentration was higher in the luteal phase than that in the follicular phase, suggesting an association of collagen metabolism with ovarian steroid hormones. Severe salpingo-oophoritis increased the serum level of the aminoterminal propeptide of type III procollagen with a decrease to normal during recovery. Elevated values were occasionally seen in endometriosis and leiomyomas. These findings indicate that the aminoterminal propeptide of type III procollagen is a relatively unspecific indicator of ovarian carcinoma. 