TPO and Iron deficiency anemia: In the Cote d'Ivoire (Zimmermann, Adou, Torresani, Zeder, & Hurrell, 2000), iron deficiency anaemia weakened the efficacy of iodine supplementation in goitrous children possibly by reducing the activity of iron‐containing thyroid peroxidase (Hess, Zimmermann, Arnold, Langhans, & Hurrell, 2002), which can impair thyroid hormone production.