SUN-370 Cushing’s Syndrome Induced Avascular Femoral Necrosis: A Missed Diagnosis as Part of Presentation

Background: Severe disintegration of articular surfaces is a well-documented complication of steroid therapy, however, endogenous hypercortisolism is also a rare and important cause of bone avascular necrosis. Case: 38 year old female, with a previous left hip arthroplasty for avascular necrosis of the femoral head diagnosed after 3 years of progressive right hip pain and limited mobility. 1 year after hip replacement, she was evaluated for secondary amenorrhea, recognized after stopping oral contraception in the context of deep venous thrombosis (DVT). The patient also presented high blood pressure (HBP) with onset 5 years earlier and reported weight gain (4 Kgs in 2 years). There was no history of infertility (IIGIIP). Physical examination revealed buffalo hump, truncal obesity, facial plethora, muscular atrophy and proximal myopathy, and easy bruising (hypocoagulated for DVT). Investigation was consistent with ATCH-independent Cushing’s syndrome (CS): abnormal overnight suppression test (21.5 µg/dL, N < 1.8 µ/dL), elevated 24 hr urinary cortisol (728.9 µg/day, N: 36.0-137.0); ACTH-concentration below detection (< 1.0 pg/mL). The patient had FT3 1.53 pg/mL (N: 1.71-3.71), FT4 0.76 ng/dL (N: 0.70-1.48), TSH 0.86 µUI/mL (0.35-4.94), FSH 4.44 mUI/mL, LH 0.53 mUI/mL, PRL 11.9 ng/mL (N: 4.8-23.3), total testosterone < 0.03 ng/mL (N: 0.06—0.82), DHEA-S 11.3 µg/dL (N: 60.9-337.0), delta-4-androstenedione < 0.3 ng/mL (N: 0.30-3.30) and HbA1c 6.8%. Urinary metanephrines and catecholamines were normal. Adrenal CT-scan showed a 25 mm lesion in the left adrenal gland, with density non-suggestive of adenoma. The patient underwent unilateral adrenalectomy and started steroid replacement. Histology revealed an adenoma of the adrenal cortex. 3 months after surgery the patient presented resolution of HBP and hypercortisolism (24 hr urinary cortisol 37,4 µg/day). Conclusion: In some cases, Cushing’s syndrome signs may go unnoticed and the diagnosis postponed. Avascular necrosis is a rare presenting feature of endogenous hypercortisolism. If left untreated, complete collapse of the femoral head may ensue, rendering the need for hip replacement in up to 70% of patients. Suspicion and recognition of atypical features is by this manner important in avoiding complications and delay in treatment of Cushing syndrome.