A 54-year-old woman comes to the physician for a health maintenance examination. She is perimenopausal and has had irregular periods beginning one year ago. 9 months ago, she commenced daily hormone replacement therapy (estradiol and medroxyprogesterone) to treat severe vasomotor symptoms. She has been taking the medroxyprogesterone intermittently because of mood changes and depression when taking it. For the past 3 months, she has had vaginal spotting 2-3 times monthly. Which of the following is the most likely explanation for the recent vaginal spotting?
Adenomyosis
Anovulation
Endometrial hyperplasia
Normal perimenopausal finding
Uterine synechiae
