The interrelationship between iron load and thyroid function is pretty well accepted, but I post here a paper showing the effect in children (can extrapolate safely to adults I think). It underlines the need for good iron loading to help rule out or confirm hypothyroidism.
Journal of Clinical and Diagnostic Research. 2018 Jan, Vol-12(1): BC01-BC05
DOI: 10.7860/JCDR/2018/32762.11023
Thyroid Function among Children with Iron Deficiency Anaemia: Pre and Post Iron Replacement Therapy
ABSTRACT
Introduction:
Metabolism of thyroid hormones and iron is quite interdependent. Data indicates that Iron Deficiency (ID) could impair thyroid metabolism.
Aim:
To investigate the possible occurrence of thyroid dysfunction among children with isolated Iron Deficiency Anaemia (IDA) of various severities, and test if the oral iron replacement therapy alone can reverse the associated thyroid function disturbances, if present or additional therapies are required.
Materials and Methods:
This prospective study was carried out on 60 children selected from the attendants to the outpatient paediatric clinics of Al-Azhar University, Assiut and Qena university hospitals, Egypt, in addition to 60 controls. Complete blood count, thyroid profile, ferritin, iron, Total Iron Binding Capacity (TIBC), Transferrin Saturation% (TFS%), unsaturated iron binding capacity and Urinary Iodine Excretion (UIE) were assessed in the studied groups at baseline, then haemoglobin level and thyroid profile repeated among the studied patients after three months of oral iron supplementation therapy. Thyroid profile and ferritin were measured using commercially available Enzyme Linked Immunosorbent Assay (ELISA) kits; while, iron, TIBC and UIE were measured using colorimetric methods.
Results:
Significant higher serum Thyroid Stimulating Hormone (TSH) levels with significant lower serum levels of Free Triiodothyronine (FT3) and Free Thyroxine (FT4) among patients versus controls (p<0.001 for all). Significant positive correlation between serum iron and FT3 (r=0.284, p<0.05) with significant negative correlations between TSH versus both serum iron (r=-0.635, p<0.001) and ferritin (r=-0.342, p<0.01). Significant decrease in the serum levels of TSH, with significant increase in the serum levels of FT3 and FT4 (p<0.001 for all) to euthyroid status following oral iron replacement therapy.
Conclusion:
Subclinical or primary hypothyroidism can occur among children suffering from moderate to severe IDA, which is reversible following oral iron replacement therapy only, without need to add thyroid replacement therapy.
