A Twin-Sibling Study on Early Growth and Hormone Levels in Adolescents

This study addresses how growth during sensitive developmental periods and genes may affect hormone levels in late adolescence. We analyzed hormone levels of dehydroepiandrosterone sulfate (DHEAS) and insulin-like growth factor-I (IGF-I), which are hypothesized to be two pathways linking early growth with adult diseases (such as type 2 diabetes and cardiovascular disease) via their effects on enhanced insulin resistance. In a twin-sibling study, we tested whether there is an association between reduced intra-uterine growth and higher DHEAS or IGF-I levels in serum during adolescence, and we examined the contribution of insulin to the link between early growth and higher DHEAS and/or IGF-I levels. Anthropometric and hormone data were collected in 18-year-old twins (184 pairs) and their non-twin siblings (n = 98). Neither birth weight nor current body size predicted serum DHEAS and IGF-I levels. In the subsample of children who showed catch-up growth in weight during infancy, the children of lower birth weight had significantly higher serum DHEAS and IGF-I levels, but these were not related to insulin levels. Variation in serum DHEAS, IGF-I and fasting insulin levels was largely explained by genetic factors (73, 78 and 61 % respectively). Thus, early growth affects hormone levels in adolescence, but only in children with catch-up growth after birth. No evidence was found that early growth enhances insulin resistance via the hormones DHEAS or IGF-I.