The rationale for endocrine therapy.

There are three major types of peritoneal endometriotic implant as distinguished by their laparoscopic and morphological characteristics; the microscopic or epithelial-type plaque, the vesicular and papular type and the fibrotic, nodular type. Fluctuations in hormone levels during the menstrual cycle and throughout hormonal therapy have differential effects on the three types of implant. After only a short period of treatment with gestrinone the active types of peritoneal endometriotic implant exhibit inactivity and involutionary changes. Regressive changes in the implants may explain the abolition of the symptoms.