The ultrastructural response of human endometrium to medroxyprogesterone acetate.

Medroxyprogesterone acetate is a steroid compound similar to progesterone in structure and function. Thirty women were given 150 mg. of medroxyprogesterone intramuscularly, and samples of the endometrium were examined by light and electron microscopy. The initial response of normal human endometrium was maturation and then inhibition. By 50 days after injection, the atrophic changes began to reverse, and by Day 90, after injection the tissue resembled normal proliferative endometrium. A previously undescribed nuclear inclusion body is present; however, its significance is unclear at this time. On the basis of ultrastructural changes, medroxyprogesterone appeared not to exert a significant influence on the endometrium past 90 days at this dosage.