Hormonal 'minipuberty' influences the somatic development of boys but not of girls up to the age of 6 years.

OBJECTIVE: Hormonal 'minipuberty' refers to a transient sex-specific surge of LH, FSH, testosterone (T) and estradiol (E2) in the first few months of life. We hypothesized a potential long-term effect of this hormonal surge on somatic parameters in the following years and therefore designed this longitudinal study. DESIGN: A hierarchical multiple regression analysis was used to analyse the potential influence of hormone concentrations during minipuberty on anthropometric measurements conducted in the first 6 years of life. PATIENTS: Thirty-five healthy babies (17 male, 18 female) were the participants. MEASUREMENTS: Testosterone, E2, SHBG, LH and FSH were measured at the ages of four, eight and 20 weeks. Anthropometric measurements were taken eight times in the first 12 months, then every 6 months up to the age of 6 years. RESULTS: A significant negative effect was found in boys between testosterone and LH levels at 8 weeks and body weight up to the age of 6 years and BMI up to 6 years (LH) and 3 years (T), respectively. A further negative effect was found between E2 levels at the age of 20 weeks and body weight as well as body length in the years that followed. A positive effect was observed between E2 at the age of 4 weeks and skinfold thickness up to the age of 6 years in boys. No significant effects were found in girls. CONCLUSIONS: The findings seem to reflect an up to now unknown long-term influence of the physiological early hormonal surge on the subsequent male but not female somatic development.

Sex hormone testosterone affects language organization in the infant brain.

Using a phonological discrimination paradigm, we show that the brain responses of 4-week-old infants systematically vary as a function of biological sex and testosterone level. Females who are generally low on testosterone demonstrated a clear phonological discrimination effect with a bilateral distribution. In male infants this effect systematically varied as a function of testosterone level. Males with high testosterone showed no discrimination effect, whereas males with low testosterone displayed a discrimination effect, which was clearly left-lateralized. The present data provide evidence for a strong influence of testosterone on language function and lateralization already present during the first weeks of life.