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The main biological function of iodine concerns its role in the biosynthesis of thyroid hormones (THs) by the thyroid gland. In addition, iodine is thought to represent one of the oldest antioxidants in living organisms. Moreover, iodine oxidation to hypoiodite (IO−) has been shown to possess strong bactericidal as well as antiviral and antifungal activity. Finally, and importantly, iodine has been demonstrated to exert antineoplastic effects in human cancer cell lines.
Age | Iodine Deficiency Disorders |
---|---|
Fetus | Abortions, stillbirths, congenital anomalies Increased perinatal mortality |
Neonate | Neonatal hypothyroidism, endemic cretinism Increased susceptibility of the thyroid gland to nuclear radiation |
Child and adolescent |
Goiter, hypothyroidism or hyperthyroidism Impaired mental function, delayed growth and puberty Increased susceptibility of the thyroid gland to nuclear radiation |
Adult | Goiter with its complications, hypothyroidism Infertility, Impaired mental function Spontaneous hyperthyroidism in the elderly Iodine-induced hyperthyroidism Increased susceptibility of the thyroid gland to nuclear radiation |
As can be seen in Table 1, hypothyroidism consequent to iodine deficiency in women causes important reproductive alterations including anovulation and reduced fertility and, when pregnancy occurs, gestational hypertension, stillbirths, and congenital anomalies, and increased perinatal mortality may be observed [37]. This may have cultural and socioeconomic consequences, compromising the life quality of parents that face the responsibility of taking care of a child with serious health problems [37][38]. From a physiological point of view, infertility occurring in iodine-deficient hypothyroid women could be seen as a protective mechanism implemented by the body to avoid hazards related to pregnancies carried out in iodine deficiency conditions. Recently, data indicating a direct association between iodine status and fertility have been reported by Mills and colleagues [39]. They observed that the time to pregnancy was significantly delayed in women with preconception UIC values <50 μg/L, with a fecundability odds ratio reduced by 46% over each menstrual cycle [39]. The detrimental effects of iodine deficiency on the development and maturation of the fetal brain are of particular relevance, representing a major preventable cause of mental defects [1][31][32][40][41][42][43][44][45][46][47].