Influence of intensive exercise on insulin-like growth factor I, thyroid and steroid hormones in female gymnasts.

Long lasting intensive physical exercise leads to growth retardation. Short-limbed girls are selected for the training as gymnasts. In a preliminary study with 9 gymnasts a significant decrease of the IGF-I concentration was found after intensive 3-day exercise. This experiment was repeated with 16 girls (11.7 +/- 0.8 years old). The higher the initial DHEA-S and E2 concentration of the gymnasts, the higher were the IGF-I basal levels. The intensive training resulted in the following changes (basal after exercise): IGF-I: 247 +/- 86-->188 +/- 77 ng/ml, T3: 2.4 +/- 0.4-->2.1 +/- 0.3 nmol/l, T4: 96 +/- 15-->98 +/- 19 nmol/l, DHEA-S: 930 +/- 636-->1018 +/- 701 nmol/l, testosterone: 1.5 +/- 0.3-->1.9 +/- 0.4 nmol/l, cortisol: 824 +/- 272-->799 +/- 219 nmol/l. During the 3-day intensive training, the parallel decrease of IGF-I and T3 concentrations in each sportswomen is particularly impressive. Apart from the sequelae of 'negative' selection, the low T3-syndrome, the anti-insulin effect of high GH secretion and the elevated cortisol concentration are responsible for the growth depression, retardation in bone age and the higher incidence of skeletal problems in these gymnasts with 'exercise-induced' delay in development.