Desmopressin Stimulation Test in a Pregnant Patient with Cushing's Disease

Hypothalamic-pituitary-adrenal axis stimulation during pregnancy complicates the investigation of Cushing's syndrome (CS). Our objective was to present the case of a pregnant patient with CS caused by a pituitary tumor in whom the desmopressin stimulation test helped in the diagnosis and led to appropriate management.

A 27-year-old woman with 9-week gestation presented with a 2-month history of proximal myopathy. She had high blood pressure, wide purplish striae, and a 1-year history of hypertension and dysglycemia. The 8 am cortisol level was 32.4 μg/dL (normal, 5-18 μg/dL), late-night salivary cortisol level was 0.7 μg/dL (11 pm, normal, <0.4 μg/dL), 24-hour urinary free cortisol levels were 237.6 μg/d (normal, 21.0-143.0 μg/d), and adrenocorticotropic hormone (ACTH) levels were 44.0 pg/mL (8 am, normal, 0-46.0 pg/mL). Nongadolinium-enhanced pituitary magnetic resonance imaging revealed no obvious lesion. The desmopressin stimulation test showed a 70% increase in ACTH levels from baseline after desmopressin administration. Pituitary magnetic resonance imaging with gadolinium revealed an 8 × 8 × 7-mm³ pituitary adenoma. Transsphenoidal surgery was performed, which revealed the presence of ACTH-positive tumor cells. After tumor removal, the patient carried on pregnancy uneventfully.

During pregnancy, ACTH levels may not be an accurate marker to help in the differential diagnosis of CS. Moreover, nongadolinium pituitary imaging might not detect small pituitary lesions.

In the present case, the desmopressin stimulation test suggested the diagnosis of Cushing's disease, which subsequently led to successful treatment. This suggests that the desmopressin test serves as a useful test for diagnosing Cushing's disease in pregnant individuals.