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

Objective The hypothalamic-pituitary-adrenal axis stimulation during pregnancy complicates the investigation of Cushing's syndrome. Our objective is to present a pregnant patient with Cushing syndrome caused by pituitary tumor in which 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 proximal myopathy for 2 months. She had high blood pressure, wide abdominal purplish striae, and proximal myopathy. Her past medical history revealed hypertension and dysglycemia for 1 year. The 8 AM cortisol was 32.4 μ g/dL (5-18), late-night salivary cortisol at 11 PM was 0.7 μ g/dL ( μ g/day (21.0-143.0). The mean ACTH concentrations at 8 AM were 44.0 pg/mL (0-46.0). Non-gadolinium enhanced pituitary magnetic resonance imaging (MRI) reported no obvious lesion. The desmopressin stimulation test showed a 70% increase in ACTH levels from baseline after desmopressin administration. The pituitary MRI with gadolinium showed an 8x8x7-mm pituitary adenoma. Transsphenoidal surgery with tumor removal was done, which showed ACTH-positive tumor cells. After the surgery, the patient carried on the pregnancy uneventfully. Discussion During pregnancy, the ACTH level may not be an accurate marker to help in the differential diagnosis of Cushing's syndrome. Moreover, non-gadolinium pituitary imaging may 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 suggested that the desmopressin test may serve as a useful test to diagnose Cushing's disease in pregnant individuals.