Human Milk Hormone Intake in the First Month of Life and Physical Growth Outcomes in Preterm Infants

Context Human milk contains hormones that regulate metabolism. Extrauterine growth restriction remains common among preterm infants, but the effect of ingesting milk hormones on preterm infant growth is poorly understood. Objective To quantify associations of longitudinal exposure to leptin, adiponectin, and insulin in milk with physical growth of preterm infants. Design/Methods In 50 preterm neonates (median gestational age 29.4 weeks), we sampled maternal milk on day-of-life 7, 14, 21, and 28 and measured hormone levels in whole milk by ELISA. Milk leptin levels were available for a subset of 18 infants. We calculated milk hormone doses by multiplying the hormone level by the milk volume ingested on each day and estimated the area under the curve (AUC) to reflect longitudinal exposure. We analyzed associations of milk hormone exposure with growth outcomes in generalized estimated equations. Main Outcome Measures Weight gain velocity and z-scores in weight, length, head circumference, and body mass index at 36 weeks’ postmenstrual age (PMA). Results Higher leptin intake was associated with greater weight gain (2.17g/kg/day [95% CI, 1.31, 3.02]) and weight z-score at 36 weeks’ PMA (0.30 [0.08, 0.53] higher z-score per tertile). Higher adiponectin intake was associated with greater length z-score (0.41 [0.13, 0.69]), however, this association was nullified after adjustment of protein and calorie intake. Higher adiponectin was associated with smaller head circumference z-score (−0.36 [−0.64, −0.07]). Insulin was not associated with growth outcomes. Conclusions Milk leptin and adiponectin exposures may affect growth of preterm infants. The long-term effects of milk hormones warrant further investigation.

Hormones in Breast Milk and Effect on Infants’ Growth: A Systematic Review

Breast milk is characterized by a dynamic and complex composition which includes hormones and other bioactive components that could influence infant growth, development, and optimize health. Among the several beneficial effects associated with prolonged breastfeeding, a 13% decrease in the risk of overweight and obesity has been reported. Recent research has focused on breast milk hormones contributing to the appetite and energy balance regulation and adiposity. Accordingly, we conducted a literature systematic review with the aim to provide an update on the effect of leptin, ghrelin, Insulin Growth Factor 1, adiponectin, and insulin on infants’ and children’s growth and body composition. The revised literature reveals contrasting findings concerning the potential role of all these hormones on modeling growth and fat mass apposition and health outcomes later in life. Further studies are needed to gain further insight into the specific role of these bioactive components in metabolic pathways related to body composition. This could help gain a further insight on infants’ growth, both in physiological and pathological settings.