Growth hormone, IGF-1, insulin, SHBG, and estradiol levels in girls before menarche

The timing of pubertal changes depends on the concerted function of the hypothalamic – pituitary – ovarian and other endocrine systems. The somatotropin system and insulin play important roles during the growth and maturation of girls. Our clinical observations have enabled us to determine and implement criteria that split the pre-menarcheal period into three phases with distinct features associated with rising levels of estrogens (pre-estrogenization, onset of estrogenization and full estrogenization). The aim of this work was to determine levels of growth hormone, insulin – like growth factor 1 (IGF-1), sex hormone binding globulins (SHBG), insulin, and estradiol in relation to somatic features in girls during subsequent phases of estrogenization. This prospective study was done in 45 healthy girls. Every three months, we recorded weight, height, BMI, maturation of tertiary sex features, estrogen-related changes in hymen, sonographic dimensions of ovaries and uterus and serum levels of growth hormone, IGF-1, SHBG, insulin, and estradiol. Onset of estrogenization was accompanied by reduction of body mass and slowing down of growth associated with declining levels of growth hormone. These changes were followed by weight gain, pubertal acceleration of growth, rising levels of growth hormone, IGF-1, insulin, and estradiol, and falling levels of SHBG.