Simple obesity is characterized by a normal or increased growth rate with an acceleration of bone age maturation. When longitudinal growth slows down in the presence of obesity, a hormonal disturbance should be sought. Despite normal growth, simple obesity is characterized by a reduced GH secretion evaluated by standard provocative tests, the administration of GH-releasing hormone or spontaneous 24-hour secretion. In obese children GH secretion may be as low as in poorly growing children with classical GH deficiency. The endocrine abnormalities along the GH axis seem to involve complex mechanisms at the hypothalamic, pituitary and peripheral level. Recent data suggest that simple obesity is associated with an increase in GH clearance and a decrease in GH synthesis and secretion. It is also associated with high insulin and insulin-like growth factor I levels which may interfere in the complex endocrine interactions. In conclusion, simple obesity is characterized by normal growth in the presence of ‘hyposomatotropism’.