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Hyperprolactinemia and amenorrhea
Milk the straightforward work-up first!
A 38-year-old woman was referred by her new gynecologist after an amenorrhea work-up. She had a history of infertility and irregular periods with eight years of unprotected intercourse and two failed in vitro fertilization procedures in the past.
The patient was then seen at a fertility clinic in a foreign country and started on metformin. However, she continued having irregular periods, and had not had a period for more than four months. A prolactin level was elevated at 80 (normal <20). The gynecologist asked whether treatment should be started for prolactinoma.
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The patient had experienced menarche at age 11. She noticed acne as a teenager and some hirsutism on her neck and face, for which she used laser treatment. She denied galactorrhea and visual changes, but complained of occasional lightheadedness and mild nausea during the past two to three months. She briefly took oral contraception in the past, which she had not tolerated due to headaches. She had never had an MRI. She denied use of herbal supplements and psychiatric medications.
The patient was a nonsmoker and did not use alcohol or recreational drugs. Medications consisted of prenatal vitamins, iron, folate and progesterone cream. Pertinent exam: blood pressure, 120/70 mm Hg; pulse, 96; height, 5’5”; weight, 173 lb; and BMI, 28.7. Physical exam was otherwise unremarkable with no relevant hirsutism.
What is the next best step in the management of this patient?
A. Pituitary MRI
B. Insulin-like growth factor-1
C. Serum or urine hCG
D. Start cabergoline 0.5 mg twice a week
E. Referral for pituitary surgery
CASE DISCUSSION:
This is a young woman who had been complaining of oligomenorrhea and now has amenorrhea. She has been actively trying to conceive. A prolactin level is elevated. While a prolactinoma is indeed consistent with this picture and a difficult fertility history, the most likely reason for amenorrhea, even in a patient with such a long history of infertility treatment, is pregnancy. Therefore, option C is the best next step.
Cabergoline lowers prolactin levels, but would not be a good choice before the diagnosis of prolactinoma (option D). A pituitary MRI would be a good step if a prolactinoma or a pituitary tumor were suspected, but the pituitary gland can sometimes be misleadingly enlarged, for instance in pregnancy (option A). However, the patient should under no circumstances be referred to pituitary surgery. Even if the patient had a prolactinoma, medical treatment should be applied first because these adenomas usually respond to dopamine agonists such as bromocryptine or cabergoline.
Bottom line: Common things are common. Indeed, this patient ended up being 14 weeks pregnant, which helps explain the elevated prolactin level in preparation for lactation as well as the elevated IGF-1 level (option B).
Ronald Tamler, MD, PhD, MBA, is an Assistant Professor in the Division of Endocrinology at Mount Sinai School of Medicine, N.Y.