Nutrition related hormonal changes in obese children

Area of Science:

• Pediatric Endocrinology
• Metabolic Disorders
• Growth Physiology

Background:

• Children with simple obesity (SO) exhibit accelerated linear growth during the prepubertal period.
• This growth occurs despite normal or elevated serum insulin-like growth factor-I (IGF-I) and paradoxically low growth hormone (GH) secretion.
• The hormonal mechanisms linking nutrition to linear growth in SO remain incompletely understood.

Purpose of the Study:

• To investigate the hormonal relationships between nutrition and linear growth in children with simple obesity (SO).
• To compare key growth and metabolic factors between SO children and children with normal short stature (NS).
• To elucidate the role of insulin, IGF-I, and their binding proteins in the growth patterns observed in SO.

Main Methods:

• Measurement of IGF-I, IGFBP-1, GHBP, and other factors in 23 SO and 19 NS children.
• Performance of oral glucose tolerance tests (OGTT) and GH-releasing factor (GRF) tests in study participants.
• Analysis of correlations between hormonal levels, GH secretion, and anthropometric data (height SD scores).

Main Results:

• SO children had significantly lower peak GH levels during GRF testing compared to NS children.
• Serum GHBP and IGF-I levels were significantly higher in SO children, correlating positively with insulin levels during OGTT.
• Basal and integrated IGFBP-1 levels were lower in SO children, while IGFBP-3 levels showed no significant difference.
• Integrated insulin, C-peptide, and glucose levels were significantly higher in SO children during OGTT.

Conclusions:

• Overnutrition in SO may lead to hyperinsulinemia, which stimulates GH receptor and IGF-I secretion, promoting growth despite low GH.
• Hyperinsulinemia might increase free IGF-I by suppressing IGFBP-1, contributing to accelerated linear growth in SO.
• Elevated free IGF-I could exert negative feedback on GH secretion, explaining the observed low GH levels in SO children.