cosyntropin and Craniopharyngioma

Recent studies suggest using lower GH cut-points for the glucagon stimulation test (GST) in diagnosing adult GH deficiency (GHD), especially in obese patients. There are limited data on evaluating GH and hypothalamic-pituitary-adrenal (HPA) axes using weight-based dosing for the GST.. To define GH and cortisol cut-points to diagnose adult GHD and secondary adrenal insufficiency (SAI) using the GST, and to compare fixed-dose (FD: 1 or 1.5 mg in patients >90 kg) with weight-based dosing (WB: 0.03 mg/kg). Response to the insulin tolerance test (ITT) was considered the gold standard, using GH and cortisol cut-points of ≥3 ng/ml and ≥18 µg/dL, respectively.. 28 Patients with hypothalamic-pituitary disease and 1-2 (n = 14) or ≥3 (n = 14) pituitary hormone deficiencies, and 14 control subjects matched for age, sex, estrogen status and body mass index (BMI) underwent the ITT, FD- and WB-GST in random order.. Age, sex ratio and BMI were comparable between the three groups. The best GH cut-point for diagnosis of GHD was 1.0 (92 % sensitivity, 100 % specificity) and 2.0 ng/mL (96 % sensitivity and 100 % specificity) for FD- and WB-GST, respectively. Age negatively correlated with peak GH during FD-GST (r = -0.32, P = 0.04), but not WB-GST. The best cortisol cut-point for diagnosis of SAI was 8.8 µg/dL (92 % sensitivity, 100 % specificity) and 11.2 µg/dL (92 % sensitivity and 100 % specificity) for FD-GST and WB-GST, respectively. Nausea was the most common side effect, and one patient had a seizure during the FD-GST.. The GST correctly classified GHD using GH cut-points of 1 ng/ml for FD-GST and 2 ng/ml for WB-GST, hence using 3 ng/ml as the GH cut-point will misclassify some GH-sufficient adults. The GST may also be an acceptable alternative to the ITT for evaluating the HPA axis utilizing cortisol cut-points of 9 µg/dL for FD-GST and 11 µg/dL for WB-GST.

Topics: Adenoma; Adrenal Insufficiency; Adult; Aged; Blood Glucose; Body Weight; Case-Control Studies; Central Nervous System Cysts; Cosyntropin; Craniopharyngioma; Dose-Response Relationship, Drug; Female; Glucagon; Hormones; Human Growth Hormone; Humans; Hydrocortisone; Hypoglycemic Agents; Hypopituitarism; Hypothalamo-Hypophyseal System; Insulin; Male; Middle Aged; Pituitary Neoplasms; Pituitary-Adrenal System; Reference Values; Sensitivity and Specificity

Since 1988, when a retrospective study of patients attending this unit was published, we have advocated the use of the short synacthen test (SST) as the primary screening investigation to detect ACTH deficiency. However, others have published comparisons of SST and insulin tolerance tests that suggest a significant false negative rate with SST, leading to concern that some patients who pass the SST are in danger from the clinical consequences of ACTH deficiency. To address this, we audited biochemical results and clinical outcome in 63 patients who did not have ACTH deficiency detected (i.e. who passed the test) by SST after pituitary surgery. Twelve of the 63 patients who passed a SST after pituitary surgery became ACTH-deficient later as diagnosed by SST: 4 within the first year, 2 of whom had received postoperative radiotherapy (3 had symptoms of tiredness and 1 was admitted to the hospital with a viral infection); 8 in yr 3-5, 7 of whom had received postoperative radiotherapy (all had either no symptoms or symptoms of tiredness alone). Thus, the predictive value of the SST in excluding ACTH deficiency is approximately 97% (2 of 63 patients who initially passed the SST were found to be ACTH-deficient within 12 months without having received postoperative radiotherapy). Only 1 patient was ill enough to require hospital admission. Setting the risk of false negatives with SST against the morbidity and manpower implications associated with insulin tolerance tests, SST remains the primary screening test for ACTH deficiency in our practice. However, a high index of clinical suspicion to detect false negative results must be maintained.

Topics: Acromegaly; Adenoma; Adolescent; Adrenocorticotropic Hormone; Adult; Aged; Aged, 80 and over; Cosyntropin; Craniopharyngioma; False Negative Reactions; Female; Humans; Hydrocortisone; Insulin; Male; Middle Aged; Pituitary Gland; Pituitary Neoplasms; Prolactinoma; Retrospective Studies; Sensitivity and Specificity