Gender difference in breast tissue size in infancy: correlation with serum estradiol.
Breast tissue in newborn infants is considered to be physiologic and mainly related to exposure to maternal hormones in utero or through breast-feeding. However, controversy exists as to whether breast tissue in later infancy is under the influence of endogenous hormones. Children at 2-4 mo of age have a surge of reproductive hormones, including estradiol, which may affect the mammary gland. In a prospective cohort study of 1126 healthy, 3-mo-old infants, breast tissue size and reproductive hormones were measured. We found that palpable breast tissue (diameter >or=3 mm) is a common physiologic condition present in 78.9% of children, significantly more frequent (p < 0.001) and larger (p < 0.001) in girls than in boys. Girls had significantly higher median estradiol levels than boys (30.0 versus 21.0 pmol/L, p < 0.001). In a multiple regression model including breast tissue size given as quartiles as the dependent variable and weight for gestational age, subscapular skinfold, weight at 3 mo of age and serum estradiol as independent variables, a gender difference was shown. In girls, the estradiol level was positively (p < 0.03) correlated to breast quartile. In boys, no correlations were found. Whether the stimulation of the mammary gland in infancy represents a developmental window that is of biologic significance for breast development and pathology in adulthood remains to be defined.
Schmidt
Ida Maria
IM
University Department of Growth and Reproduction, Rigshospitalet, Copenhagen, Denmark. rh03096@rh.dk
Chellakooty
Marla
M
Haavisto
Anne-Maarit
AM
Boisen
Kirsten Arntz
KA
Damgaard
Ida Norgil
IN
Steendahl
Ulla
U
Toppari
Jorma
J
Skakkebaek
Niels Erik
NE
Main
Katharina Maria
KM
D000886:Anthropometry; D001940:Breast / Q000033:anatomy & histology* / Q000254:growth & development; D015331:Cohort Studies; D004958:Estradiol / Q000097:blood*; D005260:Female; D005387:Finland; D005865:Gestational Age; D006801:Humans; D007223:Infant; D008297:Male; D011446:Prospective Studies; D012727:Sex Characteristics; D012885:Skinfold Thickness; D013739:Testosterone / Q000097:blood
D013739:Testosterone; D004958:Estradiol