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Difficulty: HardDiagnostic Workup and Test Sequencing

A 15-year-old girl is brought to the clinic by her mother due to the absence of menstrual periods. She has never experienced a menstrual bleed. The patient reports no cyclical pelvic pain, headaches, visual changes, or loss of smell. Her past medical history is unremarkable, and she takes no medications. She plays high school volleyball but does not engage in extreme physical training. She is at the 35th percentile for height and 45th percentile for weight. Vital signs are within normal limits. Physical examination reveals Tanner stage 1 breast development and Tanner stage 1 pubic hair. There is no clitoromegaly or severe acne. A transabdominal pelvic ultrasound is performed and demonstrates a normal-appearing prepubertal uterus, cervix, and bilateral ovaries. Which of the following is the most appropriate next step in the diagnostic workup?

  1. A
    Karyotype analysis
  2. B
    Magnetic resonance imaging of the brain
  3. C
    Progestin challenge test
  4. Serum follicle-stimulating hormone concentrationAnswer
  5. E
    Serum testosterone concentration

Answer

Serum follicle-stimulating hormone concentration
The correct answer is serum follicle-stimulating hormone (FSH) concentration. The evaluation of primary amenorrhea follows a strict diagnostic algorithm. The initial steps involve a physical examination to assess for secondary sexual characteristics (specifically breast development, which indicates estrogen exposure) and a pelvic ultrasound to determine the presence or absence of a uterus. In this patient, the ultrasound confirms that a uterus is present, but her physical examination shows absent breast development (Tanner stage 1). This combination indicates a lack of ovarian estrogen production. To determine whether the lack of estrogen is due to a primary ovarian defect (peripheral) or a lack of stimulation from the central nervous system (central), the hypothalamic-pituitary-ovarian axis must be evaluated. The most appropriate next step is to measure serum FSH. If the FSH is elevated (hypergonadotropic hypogonadism), it suggests primary ovarian insufficiency, and the next step would be a karyotype to evaluate for Turner syndrome (45,X). If the FSH is low or inappropriately normal (hypogonadotropic hypogonadism), it suggests a central cause (e.g., functional hypothalamic amenorrhea, Kallmann syndrome, or a pituitary lesion), and the next step would involve an MRI of the brain and further pituitary hormone testing.

Step-by-Step Solution

1
Identify the clinical presentation and age criteria for primary amenorrhea.
The patient is a 15-year-old female with no menarche and absent secondary sexual characteristics (Tanner stage 1 breasts), which meets the criteria for primary amenorrhea evaluation.
Evaluation is indicated at age 15 regardless of secondary sexual characteristics, or at age 13 if secondary sexual characteristics are absent.
2
Follow the primary amenorrhea diagnostic algorithm based on physical exam and initial imaging findings.
The first branch point is confirming pelvic anatomy via ultrasound. The stem states a normal uterus and ovaries are present.
The presence or absence of a uterus broadly divides the etiologies (e.g., Müllerian agenesis vs. functional hypothalamic amenorrhea).
3
Determine the next diagnostic test based on the presence of the uterus and the state of breast development.
Because the uterus is present but breast development is absent, the patient has an estrogen-deficient state.
Estrogen is required for breast development. The absence of breasts means the ovaries are not producing estrogen, either due to primary ovarian failure or lack of central stimulation.
4
Select the test that localizes the defect in the hypothalamic-pituitary-ovarian axis.
Measure the serum follicle-stimulating hormone (FSH) concentration.
An elevated FSH indicates hypergonadotropic hypogonadism (primary ovarian insufficiency, e.g., Turner syndrome), dictating a karyotype. A low or normal FSH indicates hypogonadotropic hypogonadism (central etiology), dictating an MRI of the brain and further endocrine workup.

Key Concept

In the diagnostic sequencing of primary amenorrhea, after confirming the presence of a uterus via ultrasound, the presence or absence of breast development dictates the next step. If breast development is absent, serum follicle-stimulating hormone (FSH) must be measured to distinguish between central and peripheral etiologies.
Estimated Time:1m 30s
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Diagnostic Workup and Test Sequencing

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