Reproducibility of the insulin tolerance test (ITT) for assessment of growth hormone and cortisol secretion in normal and hypopituitary adult men

The insulin tolerance test (ITT) is considered the gold standard for assessment of GH and ACTH reserve in patients with pituitary disease following pituitary surgery and is usually performed after 6-12 weeks. However, abnormal axes may not be completely recovered by then. The aim of this study was to evaluate dynamic testing 3 and 12 months after transsphenoidal pituitary surgery. Design and patients: Serial dynamic testing was performed in 36 patients (13 women, age 18-78) at 3 and 12 months after transsphenoidal surgery. Results: Compared with 3-month results, median GH peak levels during ITT after 12 months increased by 38% (P!0.05). In patients initially classified as GH deficiency (GHD), median GH peak increased after 12 months by 23% (P!0.05). At 3 and 12 months, 36% (13/36) and 47% (17/36) were GH sufficient respectively. Median cortisol peak levels after 12 months increased by 17% (P!0.01) compared with 3-month ITT. In ACTH-insufficient (AI) patients, peak cortisol levels increased significantly by 12% (P!0.05) at 12 months, and in ACTH-sufficient patients, peak cortisol levels increased significantly by 13% (P!0.05). At 12 months, there was recovery from AI in 11% of the patients, and recovery from GHD in 11% of patients. Conclusions: Serial dynamic testing results in a change in classification by ITT results in a relevant proportion of patients. Dynamic testing should be repeated during follow-up.

Section: Discussionmentioning

confidence: 99%

Recovery of pituitary function in the late-postoperative phase after pituitary surgery: results of dynamic testing in patients with pituitary disease by insulin tolerance test 3 and 12 months after surgery

Berg¹,

Meinel²,

Lahner³

et al. 2010

“…Even for the ITT, generally regarded as the 'gold standard' (27), reproducibility is a major problem (28,29), and a number of other confounders such as gender, age, and BMI are known (30). This and the known risks, as well as the demanding surveillance during the ITT, stimulated the search for other, more practical procedures.…”

Section: Biochemical Testing For Ghdmentioning

confidence: 99%

Etiology, baseline characteristics, and biochemical diagnosis of GH deficiency in the adult: are there regional variations?

Brabant

Poll²,

Jönsson³

et al. 2009

Previous work has examined potential links between the etiology of GH deficiency (GHD) and the baseline characteristics of the patients including biochemical and psychometric parameters. Using an update of the KIMS pharmaco-epidemiological database (Pfizer International Metabolic Database), we addressed the question how well such results can be generalized and whether regional differences may play a role. From 30 different countries, 13 167 GH-deficient patients were included in KIMS at the data close in December 2008. In order to explore country-specific differences of baseline characteristics documented in KIMS, separate analyses of baseline characteristics of adult-onset GHD patients (nZ7708) were performed for the six largest contributing European countries and the United States. This analysis revealed striking regional variations in the pathogenesis of the disease, clinical characteristics such as body mass index, and in the classical features of the metabolic syndrome such as blood pressure or lipid status between countries. Moreover, the approach to endocrine function testing was widely different between countries, as well as the distribution of etiologies of GHD. These data suggest that a complex relation between biochemical and clinical signs of GHD exists, and that the spectrum of adult GHD syndrome is influenced by regional diagnostic and clinical particularities. European Journal of Endocrinology 161 S25-S31

“…There are several advantages to using ITT compared with other tests. The entire HPA axis can be evaluated in addition to the GH and insulin-like growth factor 1 axis, and cortisol responses to ITT are reproducible in normal subjects (4,5). But there are some disadvantages; ITT is unpleasant for patients and close medical supervision is required during the test.…”

Section: Introductionmentioning

confidence: 99%

Can basal cortisol measurement be an alternative to the insulin tolerance test in the assessment of the hypothalamic–pituitary–adrenal axis before and after pituitary surgery?

Karaca

Tanrıverdi²,

Atmaca³

et al. 2010

Background: The aims of this study were to evaluate the validity of preoperative basal serum cortisol levels measured in predicting preoperative adrenal insufficiency and also the validity of basal serum cortisol levels and early postoperative insulin tolerance test (ITT) in predicting postoperative adrenal insufficiency. Methods: The study was prospectively designed and included 64 patients who underwent pituitary surgery for conditions other than Cushing's disease. An ITT was performed preoperatively, on the 6th postoperative day and at the 1st postoperative month. Basal serum cortisol levels were measured on the 2nd, 3rd, 4th, 5th, and 6th postoperative days. Results: Patients with a preoperative basal cortisol level of !165 nmol/l (6 mg/dl) showed insufficient cortisol response and those with levels higher than 500 nmol/l (18 mg/dl) had sufficient cortisol response to the preoperative ITT. The positive predictive value of the ITT performed on the 6th postoperative day was 69.7%, and the negative predictive value in predicting adrenal insufficiency at the 1st postoperative month was 58%. Patients were considered to have an insufficient cortisol response to ITT at the 1st postoperative month if their basal cortisol levels were !193 nmol/l (7 mg/dl) or 220 nmol/l (8 mg/dl) or 193 nmol/l (7 mg/dl) or 165 nmol/l (6 mg/dl) or 83 nmol/l (3 mg/dl) on the 2nd-6th postoperative days respectively. Conclusion: Serum basal cortisol levels may be used as the first-line test in the assessment of the hypothalamic-pituitary-adrenal axis both preoperatively and postoperatively. Dynamic testing should be limited to the patients with indeterminate basal cortisol levels.