Iron deficiency is shown to significantly reduce T4 to T3 conversion, increase reverse T3 levels, and block the thermogenic (metabolism boosting) properties of thyroid hormone (1-4). Thus, iron deficiency, as indicated by an iron saturation below 25 or a ferritin below 70, will result in diminished intracellular T3 levels. Additionally, T4 should not be considered adequate thyroid replacement if iron deficiency is present (1-4)).
See also Iron supplementation for unexplained fatigue in non-anaemic women: double blind randomised placebo controlled trial (5)
1. Dillman E, Gale C, Green W, et al. Hypothermia in iron deficiency due to altered triiodithyroidine metabolism. Regulatory, Integrative and Comparative Physiology 1980;239(5):377-R381.
2. Smith SM, Johnson PE, Lukaski HC. In vitro hepatic thyroid hormone deiodination in iron-deficient rats: effect of dietary fat. Life Sci 1993;53(8):603-9.
3. Zimmermann MB, Köhrle J. The Impact of Iron and Selenium Deficiencies on Iodine and Thyroid Metabolism: Biochemistry and Relevance to Public Health. Thyroid 2002;12(10): 867-78.
4. Beard J, tobin B, Green W. Evidence for Thyroid Hormone Deficiency in Iron-Deficient Anemic Rats. J. Nutr. 1989;119:772-778.
5. BMJ 2003;326:1124
Quote Originally Posted by reallyfedup
Is there medical papers that show that ferritin and folate need to be above halfway in their ranges in order to convert t4 into t3