IGF-I/IGFBP3/ALS deficiency in sarcopenia: low GHBP suggests GH resistance in a subgroup of geriatric patients.

CONTEXT Definition of etiological subgroups of sarcopenia may help to develop targeted treatments. Insulin like growth factor (IGF-I), IGF-binding protein 3 (IGFBP3) and acid labile subunit (ALS) build a ternary complex that mediates growth hormone (GH) effects on peripheral organs, such as muscle. Low GH binding protein (GHBP) as a marker of GH receptor number would hint towards GH resistance. OBJECTIVE Analysis of the association of IGF-I, IGFBP3, and ALS with sarcopenia. STUDY PARTICIPANTS AND SETTING 131 consecutively recruited patients of a geriatric ward for a mono-center cross-sectional analysis, non-sarcopenic patients served as controls. METHODS Sarcopenia status by hand grip strength measurement and Skeletal Muscle Index (SMI); IGF-I, IGFBP3, ALS, GH, GH binding protein (GHBP); body mass index (BMI), Activity of Daily Living (ADL), mini mental state test (MMST), routine laboratory parameters, statistical regression modelling. RESULTS Compared to controls, sarcopenic patients did not differ regarding age, sex, ADL, MMST, C reactive protein, glomerular filtration rate and albumin serum concentrations. However, sarcopenic patients had significantly lower IGF-I, IGFBP3 and ALS. IGF I and ALS associated significantly with sarcopenia and low hand grip strength, even after adjustment for age, sex, BMI and albumin, but not with low SMI. GHBP serum was low in sarcopenic patients, but normal in geriatric patients without sarcopenia. Over 60% of patients with IGF-I/ALS deficiency patients showed GH resistance. CONCLUSIONS Our data suggest that in geriatric patients low IGF-I/IGFBP3/ALS could be evaluated for causative connection of the sarcopenia spectrum. Low GHBP points towards potential GH resistance as one possible explanation of this deficiency.