Insulin sensitivity index independently predicts serum IGF-1 decreases in adolescents with long-term exercise

The study aims to investigate associations between insulin sensitivity and insulin-like growth factor-1 (IGF-1) in adolescents engaged in long-term exercise training, and to assess the impact on growth.

We conducted a prospective cohort study and followed for 1 year from a general high school (non-exercise group, age 13.3 ± 0.5 years, n = 149) and an exercise training school (exercise group, age 13.5 ± 1.3 years, n = 100). Growth indices, insulin sensitivity assessed using the Quantitative Insulin Sensitivity Check Index (QUICKI), and IGF-1 levels were obtained.

Participants in the exercise group exhibited higher QUICKI and lower IGF-1 levels. In the exercise group, IGF-1 was independently associated with QUICKI cross-sectionally at baseline and follow-up. Longitudinal analysis revealed that QUICKI at baseline was independently associated with IGF-1 levels at follow-up in the exercise group (β = -532.926, P = 0.032). Such associations were not found in non-exercise group. Additionally, no impairments in growth indices were observed in the exercise group.

Our findings suggest that QUICKI is an independent predictor of IGF-1 levels in adolescents with a long-term exercise regimen.