medwireNews: Pregnant women with high iron stores may be at an increased risk for developing gestational diabetes, a study suggests.
The association was evident from the first trimester, but was strongest in the second, closer to the time of gestational diabetes diagnosis, report Cuilin Zhang (National Institutes of Health, Bethesda, Maryland, USA) and study co-authors.
“These findings are of clinical and public health importance since they extend the observation of an association between high body iron stores and an elevated risk of glucose intolerance among non-pregnant individuals to those who are pregnant,” they write in Diabetologia.
They also say that their findings question advice to routinely give iron supplementation to all pregnant women, currently recommended by the World Health Organization among others.
The team found that ferritin levels measured during the first trimester were significantly higher in 107 women who developed gestational diabetes than in 214 controls matched for age, ethnicity, and gestational week at the time of blood collection, at 143.2 versus 118.7 pmol/L.
Although the study was case–control, it was conducted within the multiracial Eunice Kennedy Shriver National Institute of Child Health and Human Development Fetal Growth Studies–Singleton Cohort, so markers of iron status were prospectively measured, four times during pregnancy.
In the second trimester, ferritin levels remained significantly higher in cases versus controls, at 94.5 versus 78.1 pmol/L, and levels of hepcidin were also higher, at 6.4 versus 5.5 ng/mL, indicating an iron surplus in the cases.
And the ratio of soluble transferrin receptor to ferritin was significantly lower in cases than controls, at 60.0 versus 69.4.
The team says this ratio is “a measure that captures both cellular iron demand and the availability of body iron stores” and therefore “covers the full spectrum of iron homeostasis, from normal, healthy iron stores to mild or substantial functional iron deficiency.”
Having ferritin levels in the top versus the bottom quartile during the first and second trimesters significantly increased women’s likelihood of having gestational diabetes, after accounting for variables including education, family history of diabetes, and prepregnancy body mass index (odds ratio [OR]=2.43 and 3.95, respectively). The same was true for hepcidin levels during the second trimester (OR=2.61), while being in the top versus the bottom quartile of soluble transferrin receptor to ferritin ratio in this trimester was associated with a reduced odds (OR=0.15).
The researchers note that such a relationship is biologically plausible, with iron potentially able to contribute to diabetes via a number of mechanisms including oxidative stress and impairing insulin signaling and glucose metabolism.
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