Relationships between IGF-I and age, gender, body mass, fat distribution, metabolic and hormonal variables in obese patients

OBJECTIVE: To compare insulin-like growth factor-I (IGF-I) concentrations i n obese and normal subjects, and evaluate the possible relationships betwee n IGF-I concentrations and demographic, anthropometric, metabolic and hormo nal variables in obese patients. SUBJECTS AND METHODS: 286 obese outpatients (OB, 234 female and 52 male; ag e 18-71 y, body mass index (BMI) > 27 kg/m(2)) were recruited. MEASUREMENTS: BMI, waist-to-hip ratio (WHR), serum basal and oral glucose t olerance test (OGTT)-stimulated glucose and insulin concentrations, IGF-I, basal growth hormone (GH), prolactin (PRL), androgens, thyrotropin (TSH), f ree triiodothyronine (fT(3)), free thyroxine (fT(4)), free fatty acids (FFA ), triglycerides, total and high density lipoprotein (HDL)-cholesterol, 24h -urinary cortisol levels and blood pressure (BP) values were measured. IGF- I concentrations were also evaluated in a large population of 326 age-match ed controls (controls, 228 women, 98 men; age 20-86 y, BMI < 25 kg/m(2)). RESULTS: IGF-I concentrations were lower in OB than in controls (age-adjust ed mean: 21.6 vs 23.6 nmol/L, P < 0.03). However, individual IGF-I concentr ations in OB were within the age-adjusted normal range. In both groups, IGF -I concentrations were gender-independent, and showed a simple negative cor relation with age (r = -0.47). In OB, univariate analysis also shows that I GF-I concentrations were negatively correlated with BMI (r = -0.33), but no t WHR, with both basal (r = -0.16) and OGTT-stimulated glucose levels (r = -0.17), as well as FFA levels (r = -0.19), and with both diastolic and syst olic BP (both r = -0.17). In OB women, IGF-I concentrations positively corr elated with PRL (r = 0.31), testosterone (r = 0.30), androstenedione (r = 0 .30), and dehydroepiandrosterone-sulfate (DHEAS) concentrations (r = 0.41). No correlation was found with other variables. The multiple regression ana lysis showed that IGF-I concentrations were inversely and independently rel ated to age and BMI only. CONCLUSIONS: In obesity, IGF-I concentrations are slightly reduced, but gen erally within the age-adjusted normal range. IGF-I concentrations in obesit y show independent and negative relationships with age and BMI, but are not associated with fat distribution, insulin secretion, glucose tolerance, BP or risk indices for cardiovascular disease (CVD).