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Maternal iron deficiency alters circulating thyroid hormone levels in developing neonatal rats
Wang, Y., Pat Kosian, T. Nguyen, C. Anderson, J. Rumbley, S. Degitz, AND G. Anderson. Maternal iron deficiency alters circulating thyroid hormone levels in developing neonatal rats. American Thyroid Association (ATA), Denver, CO, September 21 - 25, 2016.
Thyroid hormone insufficiency and iron deficiency (FeD) during fetal and neonatal life are both similarly deleterious to mammalian development suggesting a possible linkage between iron and thyroid hormone insufficiencies. Recent published data from our laboratory demonstrate a reduction in circulating and brain thyroid hormone levels in neonatal rats when dams are fed an iron deficient diet. We now report the effects of gestational and neonatal FeD, and the effects of neonatal iron repletion, on circulating and tissue thyroid hormone levels from birth through the first month of neonatal life.Methods / Case Presentation: Gestational day 2 (G2) Sprague-Dawley rat dams were assigned to two groups. The Control group was fed a standard chow diet with 84 ppm iron while the FeD group was fed an iron deficient diet (6 ppm Fe). A separate FeD group was fed an iron replete diet starting on P14. All animals were maintained on the defined diets from G2 through weaning. Serum, brain, and thyroid tissue was harvested from neonatal male pups at postnatal day 0 (P0), P7, P14, and P30. Hemoglobin, iron, T4, T3, and rT3 levels were measured at all time points. Thyroid hormone levels were assayed by LC-MS/MS methods. Results / Discussion: Hemoglobin levels were reduced by 27% in FeD P0 pups and by 49% by P14 indicating a marked reduction in iron stores was achieved in the FeD group. We did not find significant reductions in serum T4 inFeD pups at P0, 41% reductions at P7, and 58% at P14. Dietary repletion of iron at P14 resulted in a normalization of T4 levels by P30. Similarly, serum T3 levels were reduced significantly in neonatal pups, however, reductions were more modest than T3 (36% reduction at P7 and 33% reduction at P14). No changes in hormone levels were observedat P0. rT3 levels were mostly unchanged at all time points. We are currently assessing thyroid hormone levels in brain and thyroid tissues at each time point.Conclusions: Our data demonstrate the importance of adequate iron stores in maintaining normal levels of circulating thyroid hormones during development. As the impact of inadequate thyroid hormone levels on development is well established, these data further support the inclusion of iron as a contributing factor in thyroid disease duringdevelopment.
Record Details:Record Type: DOCUMENT (PRESENTATION/SLIDE)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL HEALTH AND ENVIRONMENTAL EFFECTS RESEARCH LABORATORY
MID-CONTINENT ECOLOGY DIVISION