Dr. Ron’s Research Review – January 28, 2015

© 2015                                                                                                        

This week’s research review focuses on iron deficiency and thyroid hormones.

A study published in the American Journal Clinical Nutrition demonstrated that a consequence of iron deficiency anemia is lower body temperature related to lower thyroid hormones.
Ten women with iron-deficiency anemia, 8 with depleted iron stores (nonanemic), and 12 control women, all of similar body fatness, were exposed to a 28 degrees C water bath. The anemic women had lower rectal temperatures and concentrations of T3 and T4 at baseline and during cold exposure. Iron supplementation corrected the anemia, significantly (P = 0.03) improved rectal temperature at 100 min, and partially normalized plasma thyroid hormone concentrations. (Beard et al., 1990)

A double-blind clinical trial in Iran found that iron deficient adolescent girls had lower thyroid hormones that were improved with treatment.
The study included 94 iron deficient adolescent girls that were randomly assigned to one of two groups and treated with a 300 mg ferrous sulfate 5 times/week (n = 47) and placebo 5 times/week (n = 47) for 12 weeks. Data analysis revealed a significant increase in TT4, TT3, T3RU and a significant decrease in rT3 concentration in comparison to initial values in iron treated group (12%, p<0.001; 3.5%, p<0.001; 16%, p<0.05 and 47%, p<0.001, respectively). At 12 week there were significant differences between control and placebo in TT4, TT3, T3RU and rT3 concentrations (9.9 vs 8.4 microg dL(-1), 145.2 vs 130.4 microg dL(-1), 32.5 vs 28.4% and 23 vs 41 microg dL(-1), respectively, all p<0.001). Alterations in FT3 and TSH concentration were not significant, but concentration of FT4 revealed a significant difference between the beginning and the end of the study in iron treated group (10.3 vs 11.4, p<0.001). (Eftekhari et al., 2007)

Dr. Ron


 

Articles

Impaired thermoregulation and thyroid function in iron-deficiency anemia.
(Beard et al., 1990) Download
Ten women with iron-deficiency anemia, 8 with depleted iron stores (nonanemic), and 12 control women, all of similar body fatness, were exposed to a 28 degrees C water bath to test the hypothesis that iron-deficiency anemia impairs thermoregulatory performance. The anemic women had lower rectal temperatures than did control women (36.0 +/- 0.2 vs 36.2 +/- 0.1 degree C, respectively, P = 0.001) and a lower rate of oxygen consumption (5.28 +/- 0.26 vs 5.99 +/- 0.29 mL.min-1.kg body wt-1, respectively, P = 0.04) at 100 min of cold exposure. Plasma thyroxine and triiodothyronine concentrations were significantly (P less than 0.002) lower in anemic than in control women at baseline and during cold exposure. Responses of iron-depleted subjects were similar to those of control subjects. Iron supplementation corrected the anemia, significantly (P = 0.03) improved rectal temperature at 100 min, and partially normalized plasma thyroid hormone concentrations. Plasma catecholamines were unaffected by iron status. This experiment demonstrates a functional consequence of iron-deficiency anemia in the balance of heat production and loss and suggests that thyroid-hormone metabolism may be responsible.

Effect of iron repletion and correction of iron deficiency on thyroid function in iron-deficient Iranian adolescent girls.
(Eftekhari et al., 2007)  Download
The aim of this study was to determine whether iron supplementation in iron-deficient adolescent girls would improve thyroid function. A double-blind clinical trial was performed in a region in southern I.R. Iran. A total of 103 iron deficient participants were chosen. In all, 94 participants successfully completed this study. Participants were randomly assigned to one of two groups and treated with a 300 mg ferrous sulfate 5 times/week (n = 47) and placebo 5 times/week (n = 47) for 12 weeks. Blood samples were collected and assayed for hemoglobin, hematocrit, serum ferritin, iron, total iron binding capacity (TIBC), Thyroid stimulating hormone (TSH), total thyroxine (TT4), total triiodothyronine (TT3), free thyroid hormones (FT4 and FT3), triiodothyronine resin uptake (T3RU), reverse triiodothyronine (rT3), selenium and albumin concentrations. Statistical analysis was performed with parametric and non-parametric methods as appropriate. Data analysis revealed a significant increase in TT4, TT3, T3RU and a significant decrease in rT3 concentration in comparison to initial values in iron treated group (12%, p<0.001; 3.5%, p<0.001; 16%, p<0.05 and 47%, p<0.001, respectively). At 12 week there were significant differences between control and placebo in TT4, TT3, T3RU and rT3 concentrations (9.9 vs 8.4 microg dL(-1), 145.2 vs 130.4 microg dL(-1), 32.5 vs 28.4% and 23 vs 41 microg dL(-1), respectively, all p<0.001). Alterations in FT3 and TSH concentration were not significant, but concentration of FT4 revealed a significant difference between the beginning and the end of the study in iron treated group (10.3 vs 11.4, p<0.001). Iron supplementation improves some indices of thyroid function in iron-deficient adolescent girls.

 

References

Beard, JL, MJ Borel, and J Derr (1990), ‘Impaired thermoregulation and thyroid function in iron-deficiency anemia.’, Am J Clin Nutr, 52 (5), 813-19. PubMedID: 2239756
Eftekhari, M. H., et al. (2007), ‘Effect of iron repletion and correction of iron deficiency on thyroid function in iron-deficient Iranian adolescent girls’, Pak J Biol Sci, 10 (2), 255-60. PubMedID: 19070025