Author/Editor		Pfeifer, Marija; Kanc, Karin; Verhovec, Renata; Kocijančič, Andreja
Title		Reproducibility of the insulin tolerance test (ITT) for assessment of growth hormone and cortisol secretion in normal and hypopituitary adult men
Type		članek
Source		Clin Endocrinol (Oxf)
Vol. and No.		Letnik 54, št. 1
Publication year		2001
Volume		str. 17-22
Language		eng
Abstract		OBJECTIVE The within subject variability of the insulin tolerance test (ITT) for assessment of growth hormone (GH) status and cortisol reserve has rarely been examined, particularly in patients with hypopituitarism. This becomes important when biochemical criteria are used to determine which adults with hypopituitarism should receive GH and/or cortisol replacement. In the present study we assessed the reproducibility of GH and cortisol responses in repeated ITTs. Baseline insulin-like growth factor 1 (IGF-1) levels were also assessed for reproducibility on each occasion. DESIGN and PATIENTS Three consecutive ITTs were performed in seven normal adult men (ages 22-27 years) and two ITTs in 11 men with hypopituitarism and suspected GH deficiency (ages 2348 years). MEASUREMENTS Serum GH and IGF-1 were measured by immunoradiometric and cortisol by immunofluorimetric assays. RESULTS In normal men group peak GH responses did not differ between the three tests. There was no correlation between individual peak values. The within subject peak GH variability was between 4.6 and 59.3%, and the overall variability in 21 tests was 35%. The lowest peak GH concentration was 70 mU/I (27 micro g/I). All hypopituitary men had severe GH deficiency (all peak GH concentrations < 4 mU/l (1.5 micro g/I) in both tests). There was a highly significant correlation between individual peak GH values (r = 0.95, P < 0.0001). Basal IGF-1-values in normal and hypopituitary men were highly correlated between tests (r = 0.98, P < 0.0001). The overall within subject variability of IGF-1-values was 11.9% in normal and 22.7% in hypopituitary men. In normal men group peak cortison responses were not different between the three tests. (Abstract truncated at 2000 characters).
Descriptors		HYPOPITUITARISM INSULIN SOMATOTROPIN HYDROCORTISONE INSULIN-LIKE GROWTH FACTOR I ADULT