B.B. is a 35-year-old housewife admitted to the MCV general medicine service because of polyuria, polydipsia, polyphagia and hyperglycemia. The resident on the service obtained a history of a 70 lb. weight gain over the last 8 years, easy bruisability, and irregular menses. She had generalized obesity, with normal hair distribution, and no evidence of masculinization. BP was 150/102 and other vital signs were normal. She had mild facile plethora, but did not have dorsal or supreclavicular fat pad fullness. The skin was normal in thickness and there were no bruises. There were no violaceous striae, and she had no peripheral edema. She was treated with diet and insulin and after education was discharged for further evaluation in the endocrinology clinic. Overnight dexamethasone >> AM cortisol 18 ug/dl (normal<5ug/dl) Urine free cortisol - 201 ug/2 hrs. Other data: Dexamethasone suppression: low dose - no suppression, high dose - suppression ACTH normal: AM > 140 pg/ml; PM about 1/2 - 2/3 AM value). Inferior petrosal sinus sampling:
This reveals a gradient of ACTH levels between the peripheral sample and the petrosal sinus sample which strongly suggests that the ACTH over-production is of pituitary origin. Transsphenoidal surgery was performed, and a small mass was discovered in the right lobe of the pituitary. Postoperatively, she required brief treatment with DDAVP for transient Diabetes insipidus. Urine cortisol became normal. Over the year after surgery, she lost 80 lbs, and her requirement for insulin decreased from 80 units NPH daily to 0. Your Diagnosis ?
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