A 25-year-old woman, gravida 1 para 1, comes to the office for evaluation of amenorrhea. Twelve weeks ago, the patient vaginally delivered a healthy girl. The delivery was complicated by a retained placenta and postpartum hemorrhage that required manual extraction of the placenta and a blood transfusion. The patient is concerned as she has had no menstrual period since the delivery. She is breastfeeding exclusively and has not resumed sexual intercourse. She has no pelvic pain or vaginal discharge. Blood pressure is 100/70 mm Hg and pulse is 60/min. Examination shows a small uterus with no cervical motion tenderness and no blood in the vaginal vault. Which of the following is the most likely mechanism for this patient's amenorrhea?

Question

A 25-year-old woman, gravida 1 para 1, comes to the office for evaluation of amenorrhea.  Twelve weeks ago, the patient vaginally delivered a healthy girl.  The delivery was complicated by a retained placenta and postpartum hemorrhage that required manual extraction of the placenta and a blood transfusion.  The patient is concerned as she has had no menstrual period since the delivery.  She is breastfeeding exclusively and has not resumed sexual intercourse.  She has no pelvic pain or vaginal discharge.  Blood pressure is 100/70 mm Hg and pulse is 60/min.  Examination shows a small uterus with no cervical motion tenderness and no blood in the vaginal vault.  Which of the following is the most likely mechanism for this patient's amenorrhea?

Quizplus · Accepted Answer

11ec25c8_da0e_74ed_bc81_f3afffbfff01_MD0003_00 Lactational amenorrhea is the result of high levels of prolactin, which has an inhibitory effect on the production of the hypothalamic gonadotropin-releasing hormone (GnRH). Pulsatile GnRH release from the hypothalamus is necessary for the production and release of LH and FSH by the anterior pituitary. LH and FSH stimulate the ovary to induce ovulation. By inhibiting GnRH, and therefore LH and FSH, prolactin prevents ovulation and menstruation. Because lactation suppresses ovulation, it is a natural form of contraception for the first 6 months postpartum if the mother is breastfeeding exclusively. After the first 6 months, >50% of women resume ovulation and another form of contraception should be considered. (Choice A) Sheehan syndrome (postpartum hypopituitarism) is characterized by absent LH and FSH production as well as low prolactin levels due to postpartum hemorrhage causing pituitary infarction. The clinical consequences include inability to lactate, amenorrhea, and hypotension. This patient's normal blood pressure and ability to breastfeed suggest normal pituitary function. (Choice B) Prolactin causes continuous suppression of GnRH, which in turn results in reduced estrogen levels. Lactation can cause significant hypoestrogenism that leads patients to experience menopausal symptoms (eg, vaginal atrophy, hot flashes, night sweats). In contrast, unregulated endometrial proliferation is caused by conditions with unopposed estrogen stimulation (eg, polycystic ovary syndrome, obesity, tamoxifen) and presents as abnormal uterine bleeding. (Choice C) Intrauterine adhesions (Asherman syndrome) are caused by uterine curettage for an abortion or retained placenta. Patients typically have amenorrhea and cyclic pelvic pain due to endometrial destruction and obstructed menstrual flow. (Choice E) Beta-human chorionic gonadotropin (β-hCG) levels become undetectable 2-4 weeks after delivery. Abnormal β-hCG levels raise concern for gestational trophoblastic disease, which is associated with a molar pregnancy and presents with irregular bleeding rather than amenorrhea. Elevated β-hCG levels cause induction, not suppression, of ovulation. Educational objective: Elevated prolactin levels inhibit gonadotropin-releasing hormone release, thereby suppressing LH and FSH production. As a result, women who are breastfeeding exclusively experience anovulation and amenorrhea. References: Factors related to duration of postpartum amenorrhea among USA women with prolonged lactation. (http://www.ncbi.nlm.nih.gov/pubmed/7983102)

A 25-Year-Old Woman, Gravida 1 Para 1, Comes to the Office