|
|
The Iodine Group | |
|
Home | Orthoiodosupplementation | Body | Disease | Special | Overviews |
||
|
|
ZIMMERMANN, Kohrle
The impact of iron and selenium deficiencies on iodine and thyroid metabolism: biochemistry and relevance to public health.Zimmermann MB, Kohrle J.
“Several minerals and trace elements are essential for normal thyroid hormone metabolism, e.g., iodine, iron, selenium, and zinc. Coexisting deficiencies of these elements can impair thyroid function.
Iron deficiency impairs thyroid hormone synthesis by reducing activity of heme-dependent thyroid peroxidase. Iron-deficiency anemia blunts and iron supplementation improves the efficacy of iodine supplementation.
Combined selenium and iodine deficiency leads to myxedematous cretinism. The normal thyroid gland retains high selenium concentrations even under conditions of inadequate selenium supply and expresses many of the known selenocysteine-containing proteins. Among these selenoproteins are the glutathione peroxidase, deiodinase, and thioredoxine reductase families of enzymes. Adequate selenium nutrition supports efficient thyroid hormone synthesis and metabolism and protects the thyroid gland from damage by excessive iodide exposure. In regions of combined severe iodine and selenium deficiency, normalization of iodine supply is mandatory before initiation of selenium supplementation in order to prevent hypothyroidism. Selenium deficiency and disturbed thyroid hormone economy may develop under conditions of special dietary regimens such as long-term total parenteral nutrition, phenylketonuria diet, cystic fibrosis, or may be the result of imbalanced nutrition in children, elderly people, or sick patients.”
Effect of oral iodized oil on thyroid size and thyroid hormone metabolism in children with concurrent selenium and iodine deficiency.Zimmermann MB, Adou P, Torresani T, Zeder C, Hurrell RF. Eur J Clin Nutr. 2000 Mar;54(3):209-13. [abstract only]
"OBJECTIVES: To determine the efficacy of oral iodized oil in goitrous children who are both selenium (Se) and iodine deficient; to investigate if Se status modifies the response of iodine deficient, goitrous children to oral supplementation with iodized oil.
DESIGN: A longitudinal intervention trial. SETTING: Two rural villages in the western Cote d'Ivoire. SUBJECTS: 51 goitrous non-anemic schoolchildren with both iodine and Se deficiency.
INTERVENTION: Each child received an oral dose of 0.4 ml iodized poppyseed oil containing 200 mg of iodine. They were followed for 1 y with measurements of urinary iodine (UI), thyrotropin (TSH), thyroxine (T4), and thyroid volume by ultrasound.
RESULTS: At baseline all children were goitrous and Se deficient; median UI was 29 microg/l and mean serum Se (s.d.) was 14.8 (10.7) microg/l. After receiving iodized oil, thyroid volume decreased significantly vs baseline at 10, 15, 30 and 50 weeks (P<0.001). At 50 weeks mean percentage change in thyroid volume from baseline was-46.6% and only five children remained goitrous. Median TSH values at 5, 10, 15, 30 and 50 weeks were reduced significantly (P<0.001) compared to baseline. Among individual children the severity of Se deficiency predicted the degree of response to iodized oil. Baseline serum Se and percentage change in thyroid volume from baseline at 50 weeks were strongly correlated (r2=0.554). Baseline Se and percentage decrease in TSH from baseline at 30 weeks were also well-correlated (r2=0.467).
CONCLUSION: Although more severe Se deficiency partially blunts the thyroid response to iodine supplementation, oral iodized oil is an effective method for iodine repletion in goitrous children who are Se deficient. "
The trace element selenium and the thyroid gland.Kohrle J. Biochimie. 1999 May;81(5):527-33. Review. [abstract only]
"Apart from the essential trace element iodine, which is the central constituent of thyroid hormones, a second essential trace element, selenium, is required for appropriate thyroid hormone synthesis, activation and metabolism.
The human thyroid gland has the highest selenium content per gram of tissue among all organs.
Several selenocysteine-containing proteins respectively enzymes are functionally expressed in the thyroid, mainly in thyrocytes themselves: three forms of glutathione peroxidases (cGPx, pGPx, and PH-GPx), the type I 5-deiodinase, thioredoxin reductase and selenoprotein P. The thyroidal expression of type II 5-deiodinase still is controversial.
As thyrocytes produce H2O2 continuously throughout life an effective cell defense system against H2O2 and reactive oxygen intermediates derived thereof is essential for maintenance of normal thyroid function and protection of the gland.
In experimental animal models long-term and strong selenium deficiency leads to necrosis and fibrosis after high iodide loads.
Combined iodide and selenium deficiency such as in central Zaire is thought to cause the myxedematous form of endemic cretinism.
Inadequate selenium supply and prediagnostically low serum selenium levels are significantly correlated with the development of thyroid carcinoma and other tumors.
Though selenium supply controls expression and translation of selenocysteine-containing proteins, no direct correlation is found between selenium tissue content and expression of various thyroidal selenoproteins, indicating that other regulatory factors contribute to or override selenium-dependent expression control, e.g., in thyroid adenoma, carcinoma or autoimmune disease.
As both trace elements, iodine and selenium, were washed out from the upper layers of the soil during and after the ice ages in many regions of the world adequate supply with these essential compounds needs to be provided either by a balanced diet or supplementation."
Articles by Zimmermann on Iron
|
|
Home | Orthoiodosupplementation | Body | Disease | Special Topics | OverviewsThe Iodine Group | Books | Disclaimers | Contact Us | Search
|
||
