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A Reappraisal of Diagnosing GH Deficiency in Adults: Role of Gender, Age, Waist Circumference, and Body Mass Index

Department of Molecular and Clinical Endocrinology and Oncology (A.C., C.D.S., S.S., F.R., M.C.S., G.L.), Section of Endocrinology, University of Naples "Federico II," Italy, 80131 Naples, Italy; and Section of Endocrinology (G.A.), Department of Clinical and Experimental Medicine, University "A. Avogadro" del Piemonte Orientale, 28100 Novara, Italy

Address all correspondence and requests for reprints to: Annamaria Colao, M.D., Ph.D., Department of Molecular and Clinical Endocrinology and Oncology, "Federico II" University of Naples, via S. Pansini 5, 80131 Naples, Italy. E-mail: colao{at}unina.it.

Objective: The objective of the study was to reevaluate the diagnostic accuracy of GH peak after GHRH plus arginine test (GHRH+ARG) according to patients’ age, body mass index (BMI), and waist circumference to diagnose GH deficiency (GHD).

Outcome Measures: GH peak after GHRH+ARG and IGF-I levels reported as SD score.

Subjects: Subjects included 408 controls (218 women, 190 men, aged 15–80 yr) and 374 patients with hypopituitarism (167 women, 207 men, aged 16–83 yr).

Results: In the (elderly) healthy subjects 15–25 yr old (young), 26–65 yr old (adults) and older than 65 yr, GH cutoffs were 15.6, 11.7, and 8.5 µg/liter, 11.8, 8.1, and 5.5 µg/liter, and 9.2, 6.1, and 4.0 µg/liter, respectively, in the lean, overweight, and obese subjects. Waist circumference was the best predictor of GH peak (t = –7.6, P < 0.0001) followed by BMI (t = –6.7, P < 0.0001) and age (t = –5.7, P < 0.0001). Based on the old (<9.1 µg/liter) and new GH cutoff, 286 (76.5%) and 276 (73.8%) of 374 hypopituitary patients had severe GHD. The receiving-operator characteristic analysis showed GH cutoffs in line with the third percentile or slightly higher results so that the prevalence of GHD increased to 90.1%.

Conclusions: The results of the current study show that waist circumference and BMI are the strongest predictors of GH peak after GHRH+ARG followed by age. However, the old cutoff value of 9.0 µg/liter was in line with the new cutoffs in 95% of patients.