Growth hormone response during OGTT: the impact of assay method, gender and BMI on the estimation of reference values in patients with acromegaly and in healthy controls

Ayman M Arafat; Mathias Möhlig; Martin O Weickert; Frank H Perschel; Johannes Purschwitz; Joachim Spranger; Christian J Strasburger; Christof Schöfl; Andreas FH Pfeiffer

OC8.1

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Endocrine Abstracts (2007) 14 OC8.1

ECE2007 Oral Communications Neuroendocrinology clinical (7 abstracts)

Growth hormone response during OGTT: the impact of assay method, gender and BMI on the estimation of reference values in patients with acromegaly and in healthy controls

Ayman M Arafat ¹ , Mathias Möhlig ¹ , Martin O Weickert ¹ , Frank H Perschel ² , Johannes Purschwitz ¹ , Joachim Spranger ¹ , Christian J Strasburger ³ , Christof Schöfl ¹ & Andreas FH Pfeiffer ¹

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¹Department of Endocrinology, Diabetes and Nutrition, Charité-University Medicine Berlin, Campus Benjamin Franklin and the German Institute of Human Nutrition, Berlin, Germany; ²Department of Clinical Chemistry and Pathobiochemistry, Charité-University Medicine Berlin, Campus Benjamin Franklin, Berlin, Germany; ³Department of Clinical Endocrinology, Charité-University Medicine Berlin, Campus Mitte, Berlin, Germany.

Objectives: Besides the measurement of IGF-1, GH suppression during OGTT to assess the biochemical status in acromegaly is recommended. However, as a consequence of the development of highly sensitive and specific GH assays a critical re-evaluation of the criteria for the diagnosis and follow-up management of acromegaly is mandatory. The aim of our study was to evaluate the between-method discrepancies in GH determinations by different immunoassays considering further confounders like age, gender, and BMI.

Methods: GH was measured during a 75-g OGTT in 10 controlled and 22 uncontrolled acromegalics (12 men; age 31–62 years; BMI 21–30 kg/m²) and in 213 apparently healthy subjects (66 men; age 20–76 years; BMI 19–62 kg/m²) using 3 different assays (DPC Immulite 2000, Nichols and DSL-10-19100) that are calibrated against recommended standard (IS 98/574). Ethical Committee approval was obtained.

Results: There was a strong correlation between all assays (r=0.72–0.994, P<0.0001). However, the results obtained with DPC were, on average, 2.4-fold higher than those obtained with Nichols and 11-fold higher than those obtained with DSL. GH-nadir in controlled acromegalics was 0.98±0.26 μg/l (DPC) and 0.5±0.15 μg/l (Nichols), whereas in those with an active disease was 7.98±1.7 and 4.5±1.2, respectively. In controls, GH-nadir was 0.13±0.01 μg/l (DPC), 0.06±0.01 μg/l (Nichols) and 0.018±0.004 μg/l (DSL). Both basal and nadir-GH were significantly higher in females than in males (DPC: 2.2±0.28 vs. 0.73±0.15 μg/L and 0.16±0.013 vs. 0.08±0.01 μg/L, P<0.001, respectively). Age, BMI and waist/hip ratio correlated negatively with both basal and nadir-GH (r=−0.2, −0.32 and −0.48, P<0.01). In multiple regression analysis age, BMI and waist/hip ratio were independent predictors for both the basal and the nadir-GH (β-values ranging from −0.2 to −0.3 and −0.14 to −0.3, respectively).

Conclusions: Post-glucose GH-nadir values are assay-, gender-, age- and BMI-specific indicating the need of individual cut-off limits for each assay.