IGF-I, IGF-BP3, and GH serum levels after stimulation tests in prepubertal allergic boys

Abstract

The prevalence of short stature (SS, < 3rd percentile NCHS) among children with respiratory allergy (asthma and/or rhinitis) varies from 2% to 10%. In spite of several studies, the etiology of SS in those patients remains unknown. We evaluated growth hormone (GH) serum levels in response to two stimulating tests (standardized exercise and clonidine) in prepubertal boys (G1P1, Tanner; 8 years and 5 months to 14 years) with SS, 14 of them with respiratory allergy (A, positive skin prick test to D. pteronyssinus) and 5 nonallergic children (NA). Other causes of SS were excluded in both groups. Patients had mild asthma and/or rhinitis, and they had never received inhaled or systemic corticosteroid at any time. Tests were performed on different days, at least 1 week apart. [To prevent exercise-induced asthma, 30 min before the exercise test, allergic children inhaled disodium cromoglycate (2 mg)]. GH serum levels (Immunoassay, AIA-PACK HGH, Tosoh Co, Japan) were determined at the following times: exercise (E)-basal, 5, 15, and 30 min after exercising for 6 min; clonidine (C)-basal, 30, 60, and 90 min after clonidine (0.15 mg/m2 body surface) ingestion. A response was considered positive when GH serum levels reached the minimum of 10 ng/ml. Among (the allergic) A patients, four responded to both tests, five to C (clonidine) alone, four to E (exercise) alone and one had no response. Among NA, four had a positive response to both tests and one to C (clonidine) alone. The serum levels of insulin-like growth factor I (IGF-I) (DSL-5600 Active TM IGF-I Coated-Tube IRMA [DSL Lab Inc, USA]) and its binding protein (IGF-BP3) (DSL-6600 Active TM IGF-BP3 Coated-Tube IRMA [DSL Lab Inc, USA]) were within the normal range except for one A child. Bone age was delayed in relation to chronological age in all children, but adequate for height age. All children had delayed skeletal age in relation to chronological age, but bone age was normal for height. We concluded that in the children studied a deficiency of GH does not seem to be responsible for SS.