Soru

A 32-year-old woman, gravida 1, para 0, abortus 1, comes to the clinic to be evaluated for a 15-month history of inability to conceive. She reports that her menstrual cycles occur at regular 28-day intervals but consist of only very light spotting for 1 to 2 days. Prior to her pregnancy, her menses lasted 5 to 6 days with normal flow. Her obstetric history is significant for an elective termination of pregnancy 3 years ago at 9 weeks gestation. The procedure was complicated by heavy bleeding requiring a repeat dilation and curettage. She subsequently developed a fever and was successfully treated with intravenous antibiotics for postabortal endometritis. She takes a daily prenatal vitamin and has no other medical conditions. Her body mass index is $22 \text{ kg/m}^2$. Pelvic examination reveals a normal-appearing cervix and a mobile, normal-sized uterus without adnexal masses.

Laboratory studies show:
Follicle-stimulating hormone: $6.2 \text{ mIU/mL}$
Luteinizing hormone: $5.8 \text{ mIU/mL}$
Estradiol: $90 \text{ pg/mL}$
Thyroid-stimulating hormone: $1.8 \text{ \mu U/mL}$
Prolactin: $14 \text{ ng/mL}$

A 10-day course of oral medroxyprogesterone acetate is administered, but the patient experiences no vaginal bleeding upon cessation of the medication. Which of the following is the most likely pathophysiologic mechanism of this patient's current condition?