Urinary excretion of cortisol in acromegaly.

Free urinary cortisol excretion was measured in 19 patients with acromegaly and 19 matched controls with other pituitary disorders who were comparable with regard to age, sex, and adrenocortical response to ACTH. Excretion of cortisol was significantly higher (P less than 0.01) in the acromegalics (mean, 161 micrograms/24 h or 444 nmol/24 h) compared to the controls (mean, 82 micrograms/24 h or 226 nmol/24 h) normal subjects (mean, 85 micrograms/24 h or 235 nmol/24 h). Seven of the acromegalics had excretion of urinary cortisol exceeding the upper normal limit. The most probable cause is an increased glomerular filtration of cortisol.