The Correlation Between Iron Metabolism Indexes and Thyroid Homeostasis in Children With Sideropenia and Iodine Deficiency

Abstract

Relationships between the iron metabolism indexes and thyroid homeostasis in children were investigated. For that purpose, 68 healthy children aged 6 to 11 years were examined (35 boys and 33 girls) with adequate iron and iodine supply (n =16), latent sideropenia (n = 16), mild iodine deficiency (n = 18) and combination of latent iron deficiency and mild iodine deficiency (n = 18). We found that in 13% of boys with latent sideropenia, 78% of boys and as many girls with mild iodine deficiency, 90% of boys and 88% of girls with combined iodine and iron deficiency, the thyroid-stimulating hormone (TSH) level in blood serum ranged from 2.5 to 4.2 mIU/l under the reference data of free triiodothyronine (fT3) and thyroxine (fT4). This observation points for development of minimal thyroid insufficiency (MTI). According to the TSH/fT4 index, MTI was found in 30% of boys and 38% of girls with combined iodine and iron deficiency. These children form the group of risk for development of subclinical hypothyroidism and require mandatory individual correction of MTI by administration of potassium iodide. We found direct moderate correlations between the contents of fT3 and fT4 in serum and the hemoglobin level (Hb) in blood, between the contents of the serum iron and ferritin (r from 0.42 to 0.64). We found also an inverse moderate correlation between the serum TSH content and indexes of iron metabolism (r from –0.56 to –0.61), and a direct moderate correlation between the TSH and total serum iron-binding capacity (r = 0.54). Therefore, iron deficiency can be considered a risk factor for the development of thyroid insufficiency, which requires control of functional capacity of thyroid gland in case of iron depot depletion. The most vulnerable period for the formation of thyroid dysfunction is a prepubertal age regardless of gender. The advisability of determining the indicators of iron metabolism and its correction under conditions of latent sideropenia, mild iodine deficiency and their combination for the prevention of MTI development was justified.