US assessment of estrogen-responsive organ growth among healthy term infants: piloting methods for assessing estrogenic activity

Abstract

Background: A mother's circulating estrogen increases over the third trimester, producing physiological effects on her newborn that wane postnatally. Estrogenization might be prolonged in newborns exposed to exogenous estrogens, such as isoflavones in soy formula.

Objective: We evaluated ultrasonography for monitoring growth of multiple estrogen-responsive organs in healthy infants and developed organ-growth trajectories.

Materials and methods: We studied 38 boys (61 visits) from birth to age 6 months and 41 girls (96 visits) from birth to age 1 year using a partly cross-sectional, partly longitudinal design. We measured uterus and ovaries in girls, testes and prostate in boys, and kidneys, breasts, thymus, and thyroid in all children. We imaged all organs from the body surface in one session of < 1 h.

Results: Uterine volume decreased from birth (P < 0.0001), whereas ovarian volume increased sharply until age 2 months and then decreased (P < 0.001). Testicular volume increased with age (P < 0.0001), but prostatic volume showed minimal age trend. Breast bud diameter showed no age trend in girls but declined from birth in boys (P = 0.03).

Conclusion: US examination of multiple estrogen-responsive organs in infants in a single session is feasible and yields volume estimates useful for assessing potential endocrine disruptor effects on organ growth.

Fig. 1

US estimates of kidney sagittal length in infants versus age. Length at each visit is plotted by a symbol indicating feeding group; dashed lines connect multiple visits by the same infant; solid curves represent fitted trajectories. Top panel, boys, log₂(length) = (2.1909) + (−0.0447)*age^0.5 + (−0.0010)*age; bottom panel, girls, log₂(length) = (2.1009) + (0.0447)*age^0.5 + (−0.0012)*age

Fig. 2

US estimates of thyroid volume in infants versus age. Volume at each visit is plotted by a symbol indicating feeding group; dashed lines connect multiple visits by the same infant; solid curves represent fitted trajectories. Top panel, boys, log₂(volume) = (−1.4011) + (0.0682)*age^0.5 + (−0.0029)*age; bottom panel, girls, log₂(volume) = (−1.2666) + (0.0085)*age^0.5 + (0.0011)*age

Fig. 3

US estimates of thymus volume in infants versus age. Volume at each visit is plotted by a symbol indicating feeding group; dashed lines connect multiple visits by the same infant; solid curves represent fitted trajectories. Top panel, boys, log₂(volume) = (−0.1325) + (−0.0389)*age^0.5 + (−0.0010)*age; bottom panel, girls, log₂(volume) = (2.9498) + (0.1437)*age^0.5 + (−0.0068)*age

Fig. 4

US estimates of breast bud diameter in infants versus age. Diameter at each visit is plotted by a symbol indicating feeding group; dashed lines connect multiple visits by the same infant; solid curves represent fitted trajectories. Top panel, boys, log₂(diameter) = (−0.1325) + (−0.0389)*age^0.5 + (−0.0010)*age; bottom panel, girls, log₂(diameter) = (−0.2301) + (−0.0031)*age^0.5 + (0.0007)*age

Fig. 5

US estimates of uterine volume in infant girls versus age. Volume at each visit is plotted by a symbol indicating feeding group; dashed lines connect multiple visits by the same infant; solid curves represent fitted trajectories, log₂(volume) = (2.7759) + (−0.2298)*age^0.5 + (0.0080)*age

Fig. 6

US estimates of ovary volume in infant girls versus age. Volume at each visit by an infant is plotted by a symbol indicating feeding group; dashed lines connect multiple visits by the same infant; solid curves represent fitted trajectories, log₂(volume) = (−3.7301) + (0.6023)*age^0.5 + (−0.0266)*age

Fig. 7

US estimates of prostatic volume in infant boys versus age. Volume at each visit is plotted by a symbol indicating feeding group; dashed lines connect multiple visits by the same infant; solid curves represent fitted trajectories, log₂(volume) = (−1.2728) + (0.2479)*age^0.5 + (−0.0145)*age

Fig. 8

US estimates of testicular volume in infant boys versus age. Volume at each visit is plotted by a symbol indicating feeding group; dashed lines connect multiple visits by the same infant; solid curve represents fitted trajectory: log₂(volume) = (−2.6054) + (0.2388)*age^0.5 + (−0.0070)*age