Insulin resistance in adolescents with Down syndrome: a cross-sectional study

BACKGROUND The prevalence of diabetes mellitus is higher in individuals with Down syndrome (DS) than in the general population; it may be due to the high prevalence of obesity presented by many of them. The aim of this study was to evaluate the insulin resistance (IR) using the HOMA (Homeostasis Model Assessment) method, in DS adolescents, describing it according to the sex, body mass index (BMI) and pubertal development. METHODS 15 adolescents with DS (8 males and 7 females) were studied, aged 10 to 18 years, without history of disease or use of medication that could change the suggested laboratory evaluation. On physical examination, the pubertal signs, acanthosis nigricans (AN), weight and height were evaluated. Fasting plasma glucose and insulin were analysed by the colorimetric method and RIA-kit LINCO, respectively. IR was calculated using the HOMA method. The patients were grouped into obese, overweight and normal, according to their BMI percentiles. The EPIINFO 2004 software was used to calculate the BMI, its percentile and Z score. RESULTS Five patients were adults (Tanner V or presence of menarche), 9 pubertal (Tanner II-IV) and 1 prepubertal (Tanner I). No one had AN. Two were obese, 4 overweight and 9 normal. Considering the total number of patients, HOMA was 1.7 +/- 1.0, insulin 9.3 +/- 4.8 microU/ml and glucose 74.4 +/- 14.8 mg/dl. The HOMA values were 2.0 +/- 1.0 in females and 1.5 +/- 1.0 in males. Considering the nutritional classification, the values of HOMA and insulin were: HOMA: 3.3 +/- 0.6, 2.0 +/- 1.1 and 1.3 +/- 0.6, and insulin: 18.15 +/- 1.6 microU/ml, 10.3 +/- 3.5 microU/ml and 6.8 +/- 2.8 microU/ml, in the obese, overweight and normal groups respectively. Considering puberty, the values of HOMA and insulin were: HOMA: 2.5 +/- 1.3, 1.4 +/- 0.6 and 0.8 +/- 0.0, and insulin: 13.0 +/- 5.8 microU/ml, 7.8 +/- 2.9 microU/ml and 4.0 +/- 0.0 microU/ml, in the adult, pubertal and prepubertal groups respectively. CONCLUSION The obese and overweight, female and adult patients showed the highest values of HOMA and insulin.