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

Objective: 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.

Case Report: 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-mm pituitary adenoma. Transsphenoidal surgery was performed, which revealed the presence of ACTH-positive tumor cells. After tumor removal, the patient carried on pregnancy uneventfully.

Discussion: 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.

Conclusion: 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.