Negative magnetic resonance imaging in Cushing's disease
Milina Tancic-Gajic, Miomira Ivovic, Milos Stojanovic, Ljiljana Marina, Ana Nenezic, Zorana Arizanovic, Marija Barac & Svetlana Vujovic
Introduction: Cushings syndrome (CS) results from inappropriate exposure to excessive glucocorticoids. Untreated, it has significant morbidity and mortality.
Case report: A 38-year-old woman with a typical appearance of CS was admitted for further evaluation of hypercortisolism. The serum cortisol level was elevated without diurnal rhythm, with no adequate supression of cortisol after 1 mg dexamethasone suppresion test. Twenty-four-hour urinary free cortisol level was elevated. Differential diagnostic testing was showed ACTH-dependent lesion (ACTH=17.4/95.6 ng/l), of the pituitary origin: suppression of cortisol level to 83% of baseline in 2 days 8 mg dexamethasone suppression test and a rise in the cortisol value of 23% above basal level along with a rise in ACTH value of 85% above basal level in CRH stimulation test. Pituitary abnormalities were not observed during repeated MRI scanning. Inferior petrosal sinus (PS) sampling was performed: i) baseline ratio ACTH PS/peripferal was <2; ii) CRH stimulated ratio ACTH PS/peripheral was <3; iii) baseline intersinus ratio of ACTH, was <1.4; iv) increase in central and peripheral ACTH of more than 50% above basal level after CRH; v) Baseline ratio ACTH v. jugularis inf./peripheral >1.7. Transsphenoidal exploration and removal of the tumor was performed with hypopithyitarism as the complication. Postoperativly morning serum cortisol levels are <50 nmol/l on adequate replacement therapy with hydrocortisone, thyroxine and estro-progesterone.
Conclusions: The Cushings disease remains a challenge for diagnose and clinical management.
No single test provides an absolute distinction, but the combined results of several tests generally provide a correct diagnose.