Adolescent mothers’ adiposity appears to contribute to leptin concentrations, but not ghrelin or adiponectin, in both serum and human milk, suggests a study.
“Leptin and ghrelin in human milk may be involved in infant growth and body composition, whereas adiponectin does not appear to play a major role,” said the researchers, who evaluated 55 adolescent mother‒infant pairs at postpartum.
Dual-energy X-ray absorptiometry was used to assess maternal and infant body composition. The research team measured leptin, adiponectin, and ghrelin in maternal circulation and human milk. They also used linear regression models, adjusted for days postpartum, to explore associations between (1) maternal characteristics and hormones in maternal blood and milk and (2) milk hormones and infant measures, also adjusted for birth weight.
Serum and human milk leptin showed direct associations (r, 0.472; p=0.014), while serum and human milk ghrelin displayed inverse associations (r, ‒0.320; p=0.017). [Eur J Clin Nutr 2026;80:904-911]
Higher maternal fat mass, particularly in the arms and android region, significantly correlated with increased leptin concentrations in serum (β, 5.95, 95 percent confidence interval [CI], 1.65–10.3 and β, 5.90, 95 percent CI, 0.871–10.9, respectively) and milk (β, 0.294, 95 percent CI, 0.132‒0.455 and β, 0.280, 95 percent CI, 0.118–0.443, respectively).
Higher milk leptin appeared to result in lower infant length (β, ‒1.21, 95 percent CI, ‒2.24 to ‒0.183). Furthermore, milk ghrelin showed a weak and inverse relationship with multiple infant anthropometric measures, while no significant associations were observed for milk adiponectin.
“Taken together, the results indicate that the relationships between maternal body composition, milk hormone concentrations, and infant growth are hormone-specific and do not reflect a uniform biological process,” the researchers said.
Leptin
In earlier studies, investigators observed higher leptin concentrations in maternal circulation compared with human milk and a direct association between them, as seen in the current study. [Ann Med 2021;53:1309-1315; J Hum Lact 2021;37:714-722; Eur J Clin Nutr 2018;72:394-400]
Leptin is secreted by adipose tissue and indicative of maternal energy stores, which is why maternal adiposity is likely to contribute to higher serum leptin, which then results in increased leptin concentrations in human milk, as noted in previous studies. [J Hum Lact 2021;37:714-722; Obesity 2019;27:621-628; Front Nutr 2022;9:1025439; Eur J Clin Nutr 2021;75:180-188]
“Accordingly, we found that prepregnancy and postpartum indicators of maternal fat accumulation, including BMI, total body mass, fat mass, and particularly arm and android fat mass, were directly associated with serum and milk leptin concentrations during the first month postpartum,” the researchers said.
“These findings suggest that leptin in human milk may largely reflect maternal adiposity, although local regulatory mechanisms within the mammary gland may also contribute. This, in turn, may be relevant to early infant growth and development,” they added.
Ghrelin
The elevated concentrations of ghrelin seen in maternal circulation compared with human milk were consistent with the findings of previous studies. [J Hum Lact 2021;37:603-614; Eur J Clin Nutr 2018;72:394-400]
However, the associations between these compartments remain unclear. No studies have so far reported such relationship, while others have noted a weak or an inverse association. [Acta Paediatr 2007;96:1632-1639; J Physiol Sci 2012;62:185-190]
The lack of consensus in the literature suggests the ambiguity about ghrelin origin in human milk, according to the researchers. [Nutr Rev. 2025;83:83-111]
“Further longitudinal studies are needed to clarify these associations and their potential implications for early growth and development,” they said.