There is strong evidence that the initiation of adrenarche and gonadarche during puberty in girls depends on body mass in general and body fat in particular. The aim of this study was to analyze changes in body composition, i.e. body fat (BF), fat percentage (BF%), and lean tissue mass (LM) in girls during pre-menarcheal stages of development, including the earliest stage lacking clinical manifestations of changes in primary, secondary, and tertiary sexual characteristics. Puberty was assessed according to clinical and ultrasonographic staging of sex features developed by us. Concentrations of leptin and DHEA-S were compared and related to changes in body composition.
Subjects and methods: The study was carried out on 65 healthy girls aged 8 years and older who were followed every 3 months over a 5-year period. Age, height, weight, and BMI were recorded. Body composition (BF, BF%, LM) was determined with an infrared method. Tertiary sexual features were staged according to Tanner. Vaginal secretion was assessed according to Peter et al. Transabdominal ultrasound of the uterus and ovaries was performed with the bladder unvoided. Groups were formed according to developmental stage: E0A = pre-estrogenization (no ultrasonographic or clinical evidence of estrogenization); E0B pre-estrogenization with 'luminosity' of mucus in cervical canal; E1 = onset of estrogenization; E = full estrogenization; M = menarche +/- 3 months. Concentrations of DHEA-S and leptin were determined by radioimmunoassay.
Results: BF in prepubertal girls averaged 16%. At menarche, BF was 23.9%. Body weight at menarche was 50.6 kg and the LM/BF ratio was 3.0. High leptin concentrations were found in E0B and M groups. Leptin concentrations were lowest during full estrogenization (E). Positive correlations of leptin with BF and LM were found in girls during developmental stages preceding menarche. Mean concentration of DHEA-S started at 1,091.6 microg/l during E0A stage, dropped significantly on passing to E0B (p <0.05), and increased by menarche. DHEA-S levels were found to correlate with BF, LM, and leptin in E0A, E0B, and E1 groups. Correlation coefficients were highest (DHEA-S/BF r = 0.61; DHEA-S/LM r = 0.54; DHEA-S/LEP r = 0.57) in the E0A group, i.e. about 5 months before the appearance of 'luminosity' of cervical mucus, considered to be the first ultrasonographic sign of puberty. Apparently, leptin stimulates somatic maturation during this stage of gonadarche which terminates with menarche. The action of DHEA-S is exerted during the early stages of female puberty.