[Twin study of free insulin-like growth factor-1 on female pubertal development].

To explore the effect of insulin-like growth factor-1 (IGF-1) on female pubertal development and estimate heritability of the serum free IGF-1. The study population consisted of 427 girls aged 6 to 18 years: 132 pairs monozygotic twins, 48 pairs same-sex dizygotic twins and 67 girls with opposite-sex twin, who were all from Qingdao city, Shan-dong province. Their breast development were examined by Tanner standard and fast serum free IGF-1 contents were assayed by immunoradiometric assay (IRMA). Serum free IGF-1 concentration increased firstly and decreased later throughout puberty. The peak of free IGF-1 was 12 years old, which equals to Tanner B2. Free IGF-1 heritability of group stage B1, B2-B5, pre-menarche and post-menarche were 0.53, 0.85, 0.48, 0.83 respectively, non-classed heritability was 0.53. Fast increase of serum free IGF-1 before 12 years might be a predictor of the growth spurt and breast development. Genetic effect on female serum free IGF-1 was significant in the process of puberty.