SAT-266 Accelerated Osteoporosis - a Rare Presentation of Cushing’s Disease

Abstract

Background: Osteoporosis in post-menopausal women is usually due to bone loss from estrogen deficiency and/or age. Secondary osteoporosis (SO) is less common. Up to 30% of postmenopausal women and 50% of men with osteoporosis may have an underlying cause. Cushing’s disease (CD) is one cause of SO but rarely the presenting symptoms. The prevalence of osteoporosis (69.6% vs 37.8%) is significantly higher in patients with adrenal rather than pituitary CD. Diagnosing CD remains a challenge to physicians in spite of advances in diagnostic techniques. We report a case of CD in a post-menopausal woman presenting as accelerated osteoporosis. Clinical Case A 63-year-old Caucasian female with a history of hypertension and hysterectomy in her 50s on transdermal estrogen was referred to our Endocrine clinic for evaluation of osteoporosis and incidental finding of bilateral adrenal hyperplasia on CT spine. The patient rapidly developed kyphoscoliosis within the past 2 years. She was debilitated by pain and decreased mobility from compression fractures and spinal stenosis, and underwent thoracic and lumbar fusion surgery. On physical examination, her heart rate was 64 beats per minute, blood pressure 130/92 mmHg, weight 188 lbs. and Height 5.1 ft; a year ago it was 5.5 ft. Her face appeared round but not red. Buffalo hump and supraclavicular pad were noted. No striae or bruises noted. Healing surgical scars over the thoracic and lumbar spine were violaceous. The patient’s urine free cortisol levels, tested a month apart, were 190 mcg and 132 mcg (n 3.5-45 mcg/24h). Midnight salivary cortisol levels taken consecutive nights were 160 ng/dL and 513 ng/dL (n < 100 ng/dL). Morning Serum Cortisol and ACTH were 20.2 ug/dL and 14 pg/mL (n Cortisol 6.0-27.0 ug/dL and ACTH 7.2-63 pg/mL). Following low dose (1mg) dexamethasone suppression testing, her serum cortisol were 12.6 ug/dL, ACTH levels were 32 pg/mL and dexamethasone were 187 ng/dL (n < 30 ng/dL). 25-Hydroxy D total, TSH, Free T4, PTH intact, calcium, renin, aldosterone and SPEP levels were normal. Renal and liver functions were normal except alkaline phosphatase was 142 U/L (n 34-104 U/L). Pituitary MRI with contrast showed pituitary microadenoma. The patient was referred to a neurosurgeon and is planned for an inferior petrosal sinus sampling prior to transsphenoidal resection. Conclusion Cushing’s disease as a cause of osteoporosis is rare. Diagnosis of Cushing’s can be challenging in patients without obvious signs, as in our patient who was referred to an endocrinologist due to incidental finding of bilateral adrenal hyperplasia. A high degree of clinical suspicion is needed when investigating CD, as initial test results can be indecisive. As in our patient, initial ACTH and cortisol levels were normal, the low dose dexamethasone suppression test helped us direct our diagnosis towards CD.