The most appropriate diagnostic test to perform next is an abdominal CT scan to confirm the diagnosis of an androgen-producing adrenal tumor. Approximately 50% of androgen-producing adrenal tumors are benign adenomas, while the other half are malignant. Symptoms are usually minimal or absent in adult men. Women typically present with rapidly progressive signs and symptoms of androgen excess, including acne, hirsutism, and virilization (deepening of the voice, clitoromegaly, and male-pattern hair loss), and may also have irregular menses. In patients with clinical evidence of hyperandrogenism, biochemical testing is performed prior to imaging and should include measurement of serum testosterone and dehydroepiandrosterone sulfate (DHEAS), an adrenal androgen. This patient's biochemical evaluation has revealed marked elevation of DHEAS and mild elevation of testosterone, making an androgen-producing adrenal tumor the most likely diagnosis. DHEAS levels above 8 µg/mL (21.6 µmol/L) are diagnostic of an androgen-producing adrenal tumor. The elevated serum testosterone level seen in this patient is likely a consequence of the peripheral metabolism of adrenal androgens to testosterone. The serum testosterone level would be more than 150 to 200 ng/dL (5.2-6.9 nmol/L) in the setting of an androgen-producing ovarian tumor.
Performing a low-dose dexamethasone suppression test or pituitary MRI is not indicated because Cushing syndrome is unlikely with a normal 24-hour urine free cortisol level and in the absence of specific features of hypercortisolism (facial plethora, violaceous striae, and supraclavicular or dorsocervical fat pads).
Pelvic ultrasound is not an appropriate initial imaging test because the marked elevation of DHEAS makes an androgen-producing adrenal tumor much more likely than an ovarian neoplasm. Although the patient has a family history of polycystic ovary syndrome (PCOS), the tempo and severity of her clinical presentation are not in keeping with this disorder. Although adrenal androgen excess occurs in 30% to 40% of women with PCOS, only a mild elevation of DHEAS (3 µg/mL [8.1 µmol/L]) is expected.