Impact of different cut-off limits of peak GH after GHRH-arginine stimulatory test, single IGF1 measurement, or their combination in identifying adult patients with GH deficiency

Abstract

Objective: To evaluate the impact of different peak GH cut-off limits after GHRH-Arg test, IGF1 measurement, or their combination in identifying patients with GH deficit (GHD). Design and patients: Totally, 894 normal subjects (used for determining IGF1 normative limits) and 302 patients with suspected GHD were included. Different peak GH cut-off limits (used by European (depending on body mass index (BMI)) or North American (4.1 mg/l) Endocrine Societies, by HypoCCs (2.5 mg/l), or with 95% specificity (based on BMI), Method 1, 2, 3, or 4 respectively) and IGF1 were considered. Methods: Peak GH after GHRH-Arg and IGF1. Results: Different peak GH cut-off limits recognized different proportions of GHD (range, 24.8-62.9%). Methods 1 and 2 with high sensitivity recognized a higher proportion (95.5 and 92.5% respectively) of GHD among patients with three (T) pituitary hormone deficits (HD), whereas Method 4 (with high specificity) identified 96.7% normal subjects among those without pituitary HD; on the contrary, Method 4 identified only 75% GHD among patients with THD, whereas Method 1 recognized a high proportion (40%) of GHD among subjects without HD. Of the total patients, 82% with THD and 84.5% without HD were recognized as GHD or normal respectively by IGF1. Among the remaining patients with THD and normal IGF1, 75% was recognized as GHD by Method 1; among patients without HD and abnormal IGF1, 87.5% was identified as normal by Method 4. Overall, combination of IGF1 and Method 1 or Method 4 identified 95.5% GHD among patients with THD and 98.1% normal subjects among those without HD. Conclusions: Single peak GH cut-offs have limits to sharply differentiate GHD from normal subjects; IGF1 may be used for selecting patients to be submitted to the GHRH-Arg test; the peak GH cut-off limits to be used for identifying healthy or diseased patients depend mainly on the clinical context.

Diabetes mellitus induced by somatostatin analogue therapy is not permanent in acromegalic patients

“…Even though it is our practice to measure GH both for the diagnosis of acromegaly (both as random GH and during a oral glucose load) and during the follow‐up (as random GH measurement), for the purposes of this study, disease activity was assessed by serum IGF1 concentrations. To compare serum IGF1 concentrations over the study period, we adopted the IGF1‐index (the ratio between the IGF1 measured and the upper limit of the normal range for age), as previously reported . Remission or controlled disease was defined when the IGF1 index was ≤1.…”

“…To compare serum IGF1 concentrations over the study period, we adopted the IGF1index (the ratio between the IGF1 measured and the upper limit of the normal range for age), as previously reported. 3,16,17,20 Remission or controlled disease was defined when the IGF1 index was ≤1. On the other hand, uncontrolled disease was defined when the IGF1 index was >1.…”

Diabetes insipidus is an unfavorable prognostic factor for response to glucocorticoids in patients with autoimmune hypophysitis

“…To assess GH deficiency, a GHRH + arginine test was performed in all patients. GH cut-off values were applied according to BMI (7,8). To evaluate central hypoadrenalism, ACTH test (cosyntropin, 250 μg i.m.)…”

Pitfalls of Insulin-like Growth Factor-I and Growth Hormone Assays

“…Care has to be taken when interpreting results from these provocative tests. There is considerable variation in the cutoffs for GH stimulation tests set by different medical societies, 15 even though assay-specific cutoffs are recommended. 13,14 Unfortunately, published and well-validated data are only available for selected assay systems and testing conditions.…”