Kazumi Ninomiya

Further evidence for insulin hypersecretion not as an initial event but as a consequence of body growth and maturation in juvenile-onset obesity

According to our previous study, hyperinsulinism develops not before 10 years of age despite the presence of obesity but during the maturation years of 10-20. We aimed here at examining the growth-related islet B-cell change together with pituitary activity in non-familial juvenile obesity. Measurement of 24 h urine hormones was shown to be useful for evaluation of the diurnal hormones in plasma. In 56 non-obese and obese juveniles, a significantly positive correlation was found between age (6-18 years) and 24 h urine insulin and c-peptide, thus indicating that the age-related absolute value of body weight significantly affects insulin and c-peptide excretions both in non-obese and obese subjects. Consequently, urinary insulin and c-peptide excretions per kg of body weight were highly similar between obese and non-obese juveniles. However, when the lower specific gravity of fat mass compared with lean body mass and the relative shortage of circulating plasma in fat tissues are taken into consideration, it is obvious that obesity by itself specifically augments this physiologic B-cell maturation between 10 and 20 years of age. The possible interactions of growth hormone and pituitary gonadotropin in hyperinsulinism are discussed.