title: Low- and standard-dose corticotropin and insulin hypoglycemia testing in the assessment of hypothalamic-pituitary-adrenal function after pituitary surgery.
abstract: The optimal means of assessing the integrity of the hypothalamic-pituitary-adrenal (HPA) axis after pituitary surgery remains controversial. We compared low-dose (1 micro g iv) and standard-dose (250 micro g im) corticotropin tests performed 1 and 4-6 wk after pituitary surgery with an insulin hypoglycemia test performed at 4-6 wk. Forty-one patients (21 male and 20 female; median age, 52 yr; range, 23-73 yr) who had undergone pituitary surgery were studied (Cushing's disease excluded). Twenty-two of the 41 patients had normal cortisol responses to all tests both at 1 and 4-6 wk after surgery. Eight patients had subnormal cortisol responses to all tests. Of the 11 patients with discrepant results, seven had subnormal responses only after the low-dose corticotropin test; the remaining four patients had borderline responses to one or more tests. At 4-6 wk after surgery, subjects with a 30-min serum cortisol after standard-dose corticotropin of less than 350 nmol/liter (12.7 micro g/dl) consistently had a subnormal response to hypoglycemia, and those with a serum cortisol greater than 650 nmol/liter (23.6 micro g/dl) had a normal response to hypoglycemia. Definitive testing of the HPA axis using the standard-dose corticotropin test can be carried out provided it is performed at least 4 wk after pituitary surgery. A 30-min cortisol level greater than 650 nmol/liter (23.6 micro g/dl) indicates adequacy of the HPA axis, and a level of less than 350 nmol/liter (12.7 micro g/dl) indicates ACTH deficiency. No further testing is then required. An intermediate level of 350-650 nmol/liter (12.7-23.6 micro g/dl) warrants further assessment using the insulin hypoglycemia test.
authors.affiliation: Regional Centre for Endocrinology and Diabetes, Royal Victoria Hospital, Belfast BT12 6BA, United Kingdom.
authors.forename: C Hamish
authors.initials: CH
authors.lastname: Courtney
authors.forename: Andrew S
authors.initials: AS
authors.lastname: McAllister
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Bell
authors.forename: David R
authors.initials: DR
authors.lastname: McCance
authors.forename: Hilary
authors.initials: H
authors.lastname: Leslie
authors.forename: Brian
authors.initials: B
authors.lastname: Sheridan
authors.forename: A Brew
authors.initials: AB
authors.lastname: Atkinson
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000008:administration & dosage*; D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000032:analysis*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007004:Hypoglycemic Agents; D007030:Hypothalamo-Hypophyseal System / Q000503:physiopathology*; D007328:Insulin; D008297:Male; D008875:Middle Aged; D010902:Pituitary Gland / Q000601:surgery*; D010913:Pituitary-Adrenal System / Q000503:physiopathology*; D011184:Postoperative Period
chemical_list: D001786:Blood Glucose; D007004:Hypoglycemic Agents; D007328:Insulin; D000324:Adrenocorticotropic Hormone