A 23-year-old graduate student is evaluated in the ambulatory care clinic due to bothersom… — USMLE Step 2 CK

A 23-year-old graduate student is evaluated in the ambulatory care clinic due to bothersome facial hair and infrequent menstrual periods. Her menarche occurred at age 12, and she reports having only three to four menses per year since that time. Over the last 24 months, she has observed increasing coarse, dark hair on her upper lip, chin, and lower abdomen, prompting her to shave frequently. Her past medical history is unremarkable, and she takes no medications. Vital signs show a blood pressure of $118/76 \text{ mmHg}$ , a pulse of $74/\text{min}$ , and a respiratory rate of $14/\text{min}$ . Her body mass index is $29 \text{ kg/m}^2$ . Physical examination confirms moderate inflammatory acne over the face and back, as well as terminal hairs in a male-pattern distribution. Pelvic examination is normal, with no evidence of clitoromegaly or palpable adnexal masses. A urine human chorionic gonadotropin test is negative. Laboratory results show normal serum thyroid-stimulating hormone and prolactin levels. Which of the following is the most appropriate next step in management?

A
Prescription of combined oral contraceptives
B
Endometrial biopsy
Measurement of serum 17-hydroxyprogesteroneAnswer
D
Measurement of serum luteinizing hormone and follicle-stimulating hormone
E
Oral glucose tolerance test

Answer

Measurement of serum 17-hydroxyprogesterone

The correct answer is measurement of serum 17-hydroxyprogesterone. This patient presents with oligo-ovulation and clinical hyperandrogenism, making polycystic ovary syndrome (PCOS) the most likely diagnosis. However, PCOS is a diagnosis of exclusion. Before confirming PCOS, other causes of hyperandrogenism must be ruled out, including non-classic congenital adrenal hyperplasia (NCCAH), thyroid dysfunction, and hyperprolactinemia. Since thyroid-stimulating hormone and prolactin levels are already normal, checking 17-hydroxyprogesterone is required to exclude NCCAH (late-onset 21-hydroxylase deficiency).

Step-by-Step Solution

Identify the primary clinical presentation and generate a differential diagnosis.

The patient exhibits oligo-ovulation (irregular menses) and clinical hyperandrogenism (hirsutism, acne), pointing to polycystic ovary syndrome (PCOS) as the most likely diagnosis.

Establishing the core symptoms is necessary to guide the diagnostic workup according to standard endocrine protocols.

Apply diagnostic criteria and identify necessary exclusion tests.

PCOS is a diagnosis of exclusion. Pregnancy, thyroid disorders, and hyperprolactinemia have already been excluded by normal initial laboratory results.

The Rotterdam criteria require the exclusion of other medical conditions that can cause hyperandrogenism and irregular menses before confirming PCOS.

Select the appropriate laboratory test to rule out remaining diagnostic mimics.

Non-classic congenital adrenal hyperplasia (NCCAH) must be excluded by measuring serum 17-hydroxyprogesterone.

NCCAH, primarily caused by late-onset 21-hydroxylase deficiency, presents identically to PCOS and is a critical condition to rule out.

Key Concept

Polycystic ovary syndrome (PCOS) is a diagnosis of exclusion; confirming the diagnosis requires ruling out mimics such as thyroid dysfunction, hyperprolactinemia, and non-classic congenital adrenal hyperplasia (via 17-hydroxyprogesterone testing).

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Topics

More questions from this topic