Histologic and ultrastructural changes in human endometriotic implants treated with the antiprogesterone steroid ethylnorgestrienone (gestrinone) during 2 months.

In 20 infertile patients, the laparoscopic, histologic, and ultrastructural characteristics of endometriotic implants were studied before and after a 2-month course of therapy using 1.25 mg of the antiprogesterone steroid ethylnorgestrienone daily. Before treatment, well-differentiated endometriotic foci were seen only in implants with a rich microvascular supply. It is postulated that the degree of microvascular development may determine the differentiation of ectopic endometrium. After therapy, well-differentiated endometriotic tissues were recovered in only one patient. In all other patients, the foci remained undifferentiated, while in 11 patients striking epithelial involutionary changes were seen, such as nuclear pyknosis, extrusion of nuclear remnants, enhanced lysosomal autophagy, abortive secretion, and focal epithelial erosion. These histologic and ultrastructural changes reflect a progesterone withdrawal effect in endometriotic implants. It is thus concluded that ethylnorgestrienone induces inactivity in most endometriotic implants, while marked involution is observed in many foci. However, this subcellular involution does not result in a change of the extent of the disease according to the American Fertility Society classification system. Preliminary data concerning the pregnancy rate reveal that five patients conceived during a mean follow-up period of 6 months.