title: A rise in the glomerular filtration rate as the cause of a 'paradoxical' increase in urinary free cortisol during dexamethasone suppression in a patient with an adrenal adenoma: a case report.
abstract: A 57-year-old woman who presented with depression and hypertension for which she had received anti hypertensive therapy including diuretics was found to have Cushingoid features. All medication was stopped and subsequent investigation demonstrated markedly elevated urinary free cortisol (UFC) levels. An increase in UFC occurred in response to the low dose dexamethasone suppression test and a further increase was noted during the high dose test. Plasma cortisol levels did not change significantly. Detailed examination of the data revealed that over the 6-day testing period the plasma creatinine had fallen from 1.4 mg/dl to 0.7 mg/dl while the creatinine clearance had doubled--presumably due to withdrawal of the diuretic. When the UFC was expressed per 100 ml of plasma filtered, there was no difference between any of the daily excretions. We conclude that a concurrent increase in glomerular filtration rate is one mechanism by which a 'paradoxical' increase in UFC in response to dexamethasone suppression may occur.
mesh_terms: D000236:Adenoma / Q000503:physiopathology / Q000652:urine*; D000310:Adrenal Gland Neoplasms / Q000503:physiopathology / Q000652:urine*; D003480:Cushing Syndrome / Q000503:physiopathology / Q000652:urine*; D003907:Dexamethasone; D005260:Female; D005919:Glomerular Filtration Rate / Q000187:drug effects; D006801:Humans; D006854:Hydrocortisone / Q000652:urine*; D008875:Middle Aged
chemical_list: D003907:Dexamethasone; D006854:Hydrocortisone