Transient Postnatal Gonadal Activation and Growth Velocity in Infancy.
Transient activation of the hypothalamic-pituitary-gonadal axis with a sex steroid surge is observed in boys and girls during the first months of life. However, the role of sex steroids in the regulation of growth has not been substantiated in infancy. We tested the hypothesis that testosterone (T) surge, known to be higher in infant boys than in girls during the transient postnatal gonadal activation regulates linear growth in infants.



To characterize in detail the linear growth velocity (GV) differences between genders in the normal population in early infancy, we evaluated growth of 18 570 healthy infants (51.0% boys) with 162 003 height measurements from birth to 12 months of age. GV was monitored and compared with serially measured urinary T and estradiol levels and serum insulin-like growth factor 1 levels in 84 healthy infants (45% boys) during the first 6 months of life.



GV was significantly faster from birth to 6 months of age in boys than in girls (P ≤ .01). The greatest GV difference, 4.1 cm per year, was observed at 1 month of age, simultaneously with the peak of postnatal gonadal activation. In the mixed model analysis, GV showed a significant positive association with T in both genders (parameter estimate up to 0.62, 95% confidence interval 0.44-0.81).



These results provide a new insight into the regulation of growth in infants and elucidate a novel biological role of the transient postnatal gonadal activation in growth regulation.
Department of Pediatrics, Kuopio University Hospital, Kuopio, Finland; Department of Pediatrics and.
Panu
P
Kiviranta
Department of Pediatrics, Kuopio University Hospital, Kuopio, Finland; Department of Pediatrics and.
Tanja
T
Kuiri-Hänninen
Department of Pediatrics, Kuopio University Hospital, Kuopio, Finland; Department of Pediatrics and.
Antti
A
Saari
Faculty of Health Sciences, University of Eastern Finland, Kuopio, Finland; and.
Marja-Leena
ML
Lamidi
William Harvey Research Institute, Barts and the London, Queen Mary University of London, London, United Kingdom l.dunkel@qmul.ac.uk.
Leo
L
Dunkel
Department of Pediatrics, Kuopio University Hospital, Kuopio, Finland; Department of Pediatrics and.
Ulla
U
Sankilampi
D015415:Biomarkers / Q000378:metabolism; D001827:Body Height / Q000502:physiology*; D002657:Child Development / Q000502:physiology*; D004958:Estradiol / Q000652:urine*; D005260:Female; D006128:Growth / Q000502:physiology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008137:Longitudinal Studies; D008297:Male; D015233:Models, Statistical; D011446:Prospective Studies; D012727:Sex Characteristics; D013739:Testosterone / Q000652:urine*
D015415:Biomarkers; C583557:IGF1 protein, human; D013739:Testosterone; D004958:Estradiol; D007334:Insulin-Like Growth Factor I