Endocrine function in patients with Cushing's disease before and after treatment

To estimate the value of some commonly used tests in diagnosing Cushing's disease and to assess the outcome after treatment.

Follow-up of a consecutive group of patients for 4.1 to 109.6 months, median 34.4.

Forty-six patients assumed to have ACTH dependent hypercorticism (of 50 patients with Cushing's syndrome) were included. Forty-five underwent transsphenoidal neurosurgery. Ten were treated preoperatively with radiotherapy.

Pituitary, adrenal, thyroid and gonadal function, radiology and pituitary histology were evaluated.

One main finding was a significant correlation between the urinary excretion of cortisol before and during administration of dexamethasone. Thus patients with modestly elevated urinary cortisol excretion had an apparently normal suppression. The urinary cortisol values during the dexamethasone test were significantly related to the peak plasma cortisol concentrations at the 30-minute ACTH tests. Computed tomography failed to identify an adenoma in 10 of the 19 patients who were histologically proved to harbour a corticotroph adenoma. At 6 months after radiotherapy, clinical and biochemical improvement was noted in none. Cure was achieved in 36 after neurosurgery. Eventually, adrenalectomy was needed in eight patients. Sixteen patients developed persisting adrenal insufficiency after neurosurgery so that the total number of patients on permanent steroid substitution was 24. Post-operative thyroid and gonadal insufficiency (in men and women of fertile age) was found in 36 and 49%, respectively.

The diagnostic value of measuring the cortisol excretion during dexamethasone administration appears doubtful. The outcome after neurosurgical treatment for Cushing's disease is not entirely satisfactory. Further studies are needed to decide whether adrenalectomy as the first line of therapy should be considered relevant in some patients with Cushing's disease.