An attempt to establish cut-off points for GH concentration during the inhibition test based on the analysis of the test results performed in children without gigantism

Paula Smalczewska; Renata Stawerska; Marzena Kolasa-Kicińska; Krzysztof Jeziorny; Anna Łupińska; Joanna Krasińska; Angelika Pakuła; Sylwia Rajewska; Arkadiusz Zygmunt

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ESPE Abstracts (2024) 98 P1-162

ESPE2024 Poster Category 1 GH and IGFs 2 (11 abstracts)

An attempt to establish cut-off points for GH concentration during the inhibition test based on the analysis of the test results performed in children without gigantism.

Paula Smalczewska ¹ , Renata Stawerska ^1,2 , Marzena Kolasa-Kicińska ¹ , Krzysztof Jeziorny ^1,2 , Anna Łupińska ^1,2 , Joanna Krasińska ¹ , Angelika Pakuła ¹ , Sylwia Rajewska ¹ & Arkadiusz Zygmunt ^1,3

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¹Department of Endocrinology and Metabolic Diseases, Polish Mother's Memorial Hospital - Research Institute of Lodz, Lodz, Poland. ²Department of Paediatric Endocrinology, Medical University of Lodz, Lodz, Poland. ³Department of Endocrinology and Metabolic Diseases, Medical University of Lodz, Lodz, Poland

Introduction: A condition that causes strong inhibition of growth hormone (GH) secretion is, among others, hyperglycemia; this phenomenon is used in the diagnosis of suspected GH excess by performing a GH inhibition test after oral administration of glucose (OGTT). In a healthy adult, it has been established that the nadir of GH concentration should not exceed 1 ng/ml (0.4 ng/ml in the case of sensitive tests). It is unclear whether the same standards should apply to children (in children this test is performed to differentiate the causes of excessive growth - mainly GH-secreting pituitary adenoma with constitutional tall stature).

Material and Methods: A group of 139 children (77 girls) aged 3.1 to 17.2 years with various endocrine disorders, including mainly tall stature (n = 21), short stature (n = 23), precocious puberty (n = 10), obesity (n = 62) and menstrual disorders (n = 5). Each child underwent an OGTT after administration of glucose at a dose of 1.75 g/kg (max 75 g) with assessment of glucose and GH concentration at time points 0, 30, 60, 90 and 120 minutes. In most children, the concentration of IGF-1, which is the main mediator of the action of GH, was also assessed.

Results: In the study group, the initial GH (time point 0') ranged from 0.03 ng/ml to 10.59 ng/ml, and the maximum GH during the test (i.e. from 30 to 120 minutes) ranged from 0.03 to 13.98 ng/ml. However, the lowest values of GH concentration during the test ranged from 0.03 to 1.07 ng/dl. Therefore, the highest minimum GH value during the GH inhibition test in healthy children was 1.07 ng/ml. Fasting glycemia was found to be negatively correlated with fasting GH concentration (r =-0.207, P <0.05), but no mutual correlations were found between these factors at any other time point.

Conclusion: 1. In children with suspected GH-secreting pituitary adenoma, a GH value indicating a normal suppression test result should be considered to be below 1.1 ng/ml at any time point. 2. It seems that a GH concentration at the 0' point below 1.1 ng/ml indicates normal GH secretion and in this case there is no need to perform a GH inhibition test. 3. IGF-1 concentration in children may remain slightly above the normal range (especially in obese children) and have no clinical implications for pituitary adenoma.