Obesity is the most common cause of insulin resistance in children and adolescents. It has increasing prevalence and involves all age groups. Insulin resistance determines metabolic disturbances that are deleterious to the vasculature and other tissues. An association between insulin resistance and hyperinsulinemia on the one side and increased prevalence of thyroid nodules and enlargement of the thyroid gland on the other has been demonstrated, which could be related to the goitrogenic action of insulin and IGF-1. The aim of this study was to evaluate the prevalence of cardiovascular risk factors, the presence of hepatic steatosis and its association with hyperinsulinism. We performed a cross sectional study of 75 children between 2 and 14 years (mean 10 years) who visited the Department of Endocrinology during a span of 14 months. We analyzed the following variables: weight, height, body mass index (BMI), glucose, insulin, HOMA, acanthosis nigricans, liver transaminases, lipid profile, cortisol at 8 AM, thyroid function tests and thyroid antibodies, thyroid and abdominal ultrasonography. In our study we found that 60% of the population showed elevated insulin levels (> 15 mu IU/ml) with progressive increase in the prevalence of acanthosis nigricans, and 12.3% showed inappropriate glucose levels. Ninety per cent of patients with heterogeneous thyroid ultrasonography had hyperinsulinemia (p < 0.05), and thyroid nodules were found in 5 of them (9.8%). We assessed the possible relationship between thyroid nodules and hyperinsulinism, and found a positive association in 80% of the cases. Childhood obesity should be considered a public health problem.