A 26-year-old nulligravid woman presents to the gynecologist reporting the absence of mens… — USMLE Step 2 CK

A $26$ -year-old nulligravid woman presents to the gynecologist reporting the absence of menses for the past $6$ months. Prior to this, she had regular menstrual cycles occurring every $28$ days. Over the same $6$ -month period, she has noted a significant increase in thick, dark hair on her face, chest, and abdomen, as well as a noticeable deepening of her voice. She has also experienced a receding hairline. She has no significant past medical history and takes no medications or supplements. Vital signs are within normal limits. Her BMI is $23 \text{ kg/m}^2$ . Physical examination reveals temporal balding, severe hirsutism on the face and trunk, and clitoromegaly. Bimanual pelvic examination is limited by patient discomfort but reveals no obvious adnexal masses. A urine human chorionic gonadotropin test is negative. Serum thyroid-stimulating hormone (TSH) and prolactin levels are within normal limits. Which of the following is the most appropriate next step in the evaluation of this patient?

A
Calculation of the serum luteinizing hormone to follicle-stimulating hormone ratio
B
Measurement of early morning serum 17-hydroxyprogesterone
C
Endometrial biopsy
Measurement of serum testosterone and dehydroepiandrosterone sulfateAnswer
E
Measurement of serum free thyroxine

Answer

Measurement of serum testosterone and dehydroepiandrosterone sulfate

The correct next step is the measurement of serum testosterone and dehydroepiandrosterone sulfate (DHEAS). This patient presents with secondary amenorrhea and rapid-onset, severe hyperandrogenism leading to frank virilization (evidenced by clitoromegaly, deepening of the voice, and temporal balding). While mild, chronic hirsutism is commonly caused by polycystic ovary syndrome (PCOS) or non-classic congenital adrenal hyperplasia (NCCAH), rapid-onset virilization is a major red flag for an androgen-secreting neoplasm. These tumors can arise from the ovaries (e.g., Sertoli-Leydig cell tumors) or the adrenal glands (e.g., adrenal adenoma or carcinoma). Measuring serum testosterone and DHEAS helps differentiate the source: markedly elevated testosterone points to an ovarian etiology, whereas markedly elevated DHEAS points to an adrenal etiology.

Step-by-Step Solution

Identify the patient's primary presenting syndrome.

The patient has secondary amenorrhea accompanied by rapid-onset (

6

months) severe hyperandrogenism, characterized by frank virilization (clitoromegaly, deepening voice, male-pattern balding).

Recognizing the severity and tempo of hyperandrogenism is critical for narrowing the differential diagnosis.

Differentiate between benign and neoplastic causes of hyperandrogenism.

Benign causes like polycystic ovary syndrome (PCOS) and non-classic congenital adrenal hyperplasia (NCCAH) typically present with a slow, insidious onset of mild to moderate hirsutism and acne, lacking frank virilization. Rapid-onset virilization strongly suggests an androgen-secreting neoplasm.

This distinction prevents misdiagnosis of common conditions like PCOS in patients harboring a potentially life-threatening tumor.

Determine the necessary laboratory tests to identify the source of the suspected neoplasm.

Measurement of serum total testosterone and dehydroepiandrosterone sulfate (DHEAS) is indicated.

Markedly elevated testosterone levels (typically >

150 \text{ ng/dL}

) suggest an ovarian source (e.g., Sertoli-Leydig cell tumor), whereas markedly elevated DHEAS levels (typically >

700 \text{ mcg/dL}

) suggest an adrenal source (e.g., adrenal adenoma or carcinoma).

Key Concept

Rapid-onset hirsutism with signs of virilization (such as clitoromegaly, temporal balding, and deepening of the voice) requires immediate evaluation for an androgen-secreting tumor of ovarian or adrenal origin using serum testosterone and DHEAS levels.

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