Pituitary function after transsphenoidal surgery including measurement of basal morning cortisol as predictor of adrenal insufficiency.

Patients with pituitary adenomas undergoing transsphenoidal surgery require pre- and post-surgery examination of pituitary hormones. There is currently no consensus on how to evaluate the adrenal axis post-surgery. The aims of this study were to investigate factors that may predict postoperative adrenal insufficiency (AI) and to investigate the overall effect of transsphenoidal surgery on pituitary function. One hundred and forty-three consecutive patients who had undergone transsphenoidal surgery for pituitary adenomas were included. Data on tumour size, pituitary function pre-surgery, plasma basal cortisol measured within 48 h post-surgery and pituitary function 6 months post-surgery were collected. Patients with AI prior to surgery, perioperative glucocorticoid treatment, Cushing's disease and no re-evaluation after 1 month were excluded (n = 93) in the basal cortisol analysis. Low plasma basal cortisol post-surgery, tumour size and previous pituitary surgery were predictors of AI (all P < 0.05). A basal cortisol cut-off concentration of 300 nmol/L predicted AI 6 months post-surgery with sensitivity and negative predictive value of 100%, specificity of 81% and positive predictive value of 25%. New gonadal, thyroid and adrenal axis insufficiencies accounted for 2, 10 and 10%, respectively. The corresponding recovery rates were 17, 7 and 24%, respectively. Transsphenoidal surgery had an overall beneficial effect on pituitary endocrine function. Low basal plasma cortisol measured within 48 h after surgery, tumour size and previous surgery were identified as risk factors for AI. Measurement of basal cortisol post-surgery may help to identify patients at risk of developing AI.