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Difficulty: MediumMenstrual Cycle Abnormalities and Contraception

A 20-year-old woman comes to the clinic because of irregular menstrual periods and increased facial hair. Her menarche occurred at age 13. Her periods were initially regular but have become increasingly irregular over the past two years, now occurring every 3 to 4 months. She has also noticed coarse, dark hair growing on her chin and chest, and she has struggled with severe acne that has not responded to over-the-counter topical treatments. She takes no medications and has no other medical conditions. Vital signs show a blood pressure of 122/78 mmHg, pulse of 76/min, and a BMI of 31 kg/m². Physical examination reveals hirsutism on the face and chest and moderate inflammatory acne on the back. There is no clitoromegaly or deepening of the voice. Pelvic examination is unremarkable. A urine pregnancy test is negative. Initial laboratory studies show a normal serum thyroid-stimulating hormone (TSH) level and a normal serum prolactin level. Which of the following is the most appropriate next step in the evaluation of this patient?

  1. Measurement of serum 17-hydroxyprogesteroneAnswer
  2. B
    Initiation of a combined estrogen-progestin oral contraceptive
  3. C
    Endometrial biopsy
  4. D
    Measurement of serum free thyroxine (T4)
  5. E
    Reassurance and routine follow-up

Answer

Measurement of serum 17-hydroxyprogesterone
The correct answer is measurement of serum 17-hydroxyprogesterone. The patient's presentation of oligomenorrhea and clinical hyperandrogenism is highly suspicious for polycystic ovary syndrome (PCOS). However, PCOS is a diagnosis of exclusion. According to diagnostic guidelines, other disorders that can cause hyperandrogenism and oligo-ovulation must be explicitly excluded. These include thyroid disease (excluded by a normal TSH), hyperprolactinemia (excluded by a normal prolactin), and non-classic congenital adrenal hyperplasia (NCAH). NCAH is caused by a partial deficiency of 21-hydroxylase and can present identically to PCOS with post-pubertal onset of hirsutism, acne, and menstrual irregularities. Therefore, measuring a morning serum 17-hydroxyprogesterone level is the mandatory next step to rule out NCAH before finalizing a diagnosis of PCOS.

Step-by-Step Solution

1
Identify the patient's primary syndrome
The patient presents with oligomenorrhea and clinical hyperandrogenism (hirsutism, acne).
Recognizing the symptom cluster is the first step in applying diagnostic criteria.
2
Review the completed preliminary workup
Pregnancy, primary thyroid disorders, and hyperprolactinemia have been successfully ruled out via negative beta-hCG, normal TSH, and normal prolactin levels.
These are common causes of secondary amenorrhea and oligomenorrhea that must be excluded initially.
3
Determine the necessary test to complete the evaluation
Serum 17-hydroxyprogesterone must be measured.
Polycystic ovary syndrome is a diagnosis of exclusion. Non-classic congenital adrenal hyperplasia can present identically and must be systematically ruled out.

Key Concept

Polycystic ovary syndrome (PCOS) is a diagnosis of exclusion; conditions such as non-classic congenital adrenal hyperplasia must be ruled out by measuring 17-hydroxyprogesterone before confirming the diagnosis.
Estimated Time:1m 15s
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Topics

Menstrual Cycle Abnormalities and Contraception

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