Gender Difference in Breast Tissue Size in Infancy: Correlation with Serum Estradiol

Abstract

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 Ն3 mm) is a common physiologic condition present in 78.9% of children, significantly more frequent (p Ͻ 0.001) and larger (p Ͻ 0.001) in girls than in boys. Girls had significantly higher median estradiol levels than boys (30.0 versus 21.0 pmol/L, p Ͻ 0.001). In a multiple regression model including

Establishment of Normative Data for the Amount of Breast Tissue Present in Healthy Children up to Two Years of Age

“…4 Furthermore, different investigative methods in the literature have contributed to results that are not comparable. 7 Palpable breast tissue was found to be a common physiological phenomenon in our study subjects of both genders, though more commonly in females (present at 83.8% of female visits compared to 75.2% of male visits). The percentage of those with palpable tissue and breast tissue size declined with age, and after 10 months, the 50 th percentile for breast unit size in males was nearly zero.…”

Gender-Related Changes in Magnetocardiographically Determined Fetal Cardiac Time Intervals in Intrauterine Growth Retardation

“…Animal studies have shown that elevated estradiol levels may prolong atrial effective refractory periods (28) and differences in estradiol concentrations between the genders in infants have been observed (29). It is thus conceivable that prenatal differences in such hormone levels in association with gender and growth retardation may lead to the observed differences in atrial conduction observed here.…”

Kidney growth in 717 healthy children aged 0?18�months: a longitudinal cohort study

“…All pregnant women of Danish origin, geographically belonging to the hospital referral area, and not referred because of expected complications in pregnancy, were consecutively recruited during their first trimester. The children were part of an ongoing comprehensive cohort study investigating kidney size and malformations, genital development and malformations, and general body growth [10,11,12].…”