Animal model of uterine adenomyosis: induction of the lesion in rats by ectopic pituitary isografting.

Adenomyosis is a benign pathologic disorder of the uterine endometrial tissues whereby endometrial components, such as glands and stroma, invade the myometrium. Transplantation of a single anterior pituitary gland into the uterine lumen induced adenomyosis in six of eight Wistar rats 12 months after the grafting. Adenomyotic changes were not observed in six sham-operated control rats. Electron microscopic observations indicated that cells of the inner layer of the myometrium were reduced in size and irregularly shaped in the areas bearing adenomyotic changes. In pituitary-grafted rats, healthy corpora lutea remained in the ovaries, whereas control rats had degenerating ovaries. These findings are consistent with the results of pituitary-grafted mice reported previously and support our assertion that a hormonal milieu induced by pituitary grafting is favorable for development of uterine adenomyosis.