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.