Transient gonadal activation and infant growth velocity

Background: Hypothalamic-pituitary-gonadal axis is activated during the first 6 months of life, called as mini-puberty in which reproductive hormone levels may reach to adult levels. Although, our understanding of the pathophysiology of sex steroids interaction with growth in puberty is increasing, very little is known about the relationship between sex steroids and growth at this period of life. Material and Methods: 142 (67 girls, 75 boys) healthy appropriate-for-gestational age neonates were included. Insulin-like growth factor 1(IGF-1), insulin-like growth factor 3 (IGFBP-3), luteinizing hormone (LH), follicle stimulating hormone (FSH), total testosterone (TT) and estradiol (E2) levels were measured at postnatal 2nd month of life. In all cases height and weight were measured at the 1st, 2nd, 4th, 6th, 9th and 12th months of age. GV was monitored and compared with sex steroids and growth factors. Results: The mean LH and TT levels were significantly higher in boys than girls (P = 0.001). In girls, the mean FSH level was significantly higher than in boys (P = 0.001). There was no statistically significant difference between the mean E2, IGF-1 and IGFBP-3 levels in boys and girls (p> 0.05). The GV was significantly faster from birth to 6 months of age in boys than in girls (P <0.05). The highest GV was observed at 1 and 2 months of age, simultaneously with the peak of postnatal gonadal activation. There was a positive correlation between GV and TT in both sexes (P <0.05). Conclusion: These results may provide a new perspective on the effect of transient gonadal activation on infant growth velocity.