Is biochemical hypoglycemia necessary during an insulin tolerance test?

ABSTRACT Objective The insulin tolerance test (ITT) has been accepted as the gold standard test for assessing the integrity of the growth hormone (GH) - insulin-like growth factor (IGF-1) axis and the hypothalamic-pituitary-adrenal (HPA) axis. The goal of the test is to achieve clinical and biochemical hypoglycemia at a blood glucose level ≤ 40 mg/dL to effectively and correctly assess the HPA and GH-IGF-1 axes. In this study, the GH and cortisol responses of patients who achieved and failed to achieve biochemical hypoglycemia during an ITT were compared. Subjects and methods One hundred thirty-five patients with pituitary disorders were included in the study. Samples for blood glucose levels were obtained after clear symptoms of clinical hypoglycemia developed. The patients were enrolled in the hypoglycemic and nonhypoglycemic groups according to whether their plasma glucose level ≤ 40 mg/dL or > 40 mg/dL during an ITT, and the groups were compared in terms of their GH and cortisol responses. Results The mean age, body mass index and waist circumference of the two patient groups were found to be similar. The mean blood glucose level was significantly lower in the hypoglycemic group than in the nonhypoglycemic group (19.3 and 52.0 mg/dL, respectively). When the two groups were compared in terms of peak cortisol and GH responses, no statistically significant differences were found. Conclusion The data presented suggest that clinically symptomatic hypoglycemia is as effective as biochemically confirmed hypoglycemia during an ITT. Arch Endocrinol Metab. 2020;64(1):82-8

Clinical characteristics and diagnostic analysis of thyrotropinoma / 中华内分泌代谢杂志

Objective To analyze clinical charaCteristics and diagnostic experience on thyrotropinoma (TSHoma).Methods Clinical characteristics,laboratory findings,diagnostic experience,and surgical outcome were summarized from 16 cases of TSHoma in our hospital from January 2006 to September 2011.Results ( 1 )Among 16 cases ( 9 male,7 female ) aged ( 51.63 ± 13.23 ) years,14 ( 87.5 ％ ) cases presented with hyperthyroidism and 2 were diagnosed by physical examination. None of them had exophthalmos, acropachy, or pre-tibial myxedema.( 2 ) Serum FT4 and FT3 levels were all above normal range with serum TSH ( 4.37 ± 2.77 ) μIU/ml.There were 25％ (4/16) cases with positive serum thyroglobulin antibody and/or thyroid peroxidase antibody,none with positive TSH receptor antibody.TRH stimulating test was performed in 9 cases,3 were with positive response ( peak TSH level increased by 5.45-9.20 μIU/ml compared with baseline),and 6 without response (peak TSH level increased by -0.01-3.15 μIU/ml compared with baseline).TSH was suppressed to 27.15％ (5.19％-99.15 ％ ) of the baseline in 11 cases in which somatostatin suppression test was carried out.Prolactin and insulin-like growth factor-Ⅰ levels were increased in 2 cases.MRI performed in 15 patients showed 10 cases of microadenomas and 5 cases of pituitary adenoma.A mass in nasal cavity was found in one case,where no mass was found in the pituitary.( 3 )Surgery was made in 11 cases ( 9 patients underwent transsphenoidal operation,one craniotomy,and one underwent operation via endoscopic nasal septum ). All patients (11/11) were proved to yield pituitary adenoma pathologically.Conclusion Thyrotropinoma should be considered in hyperthyroidism with unsuppressed TSH level,and dynamic tests facilitated early diagnosis.Ectopic thyrotropinoma shoull be considered when normal pituitary morphology was shown by MRI.