Brain Findings Associated with Iodine Deficiency Identified by Magnetic Resonance Methods: A Systematic Review

Abstract

Objectives: Iodine deficiency (ID) is a common cause of preventable brain damage and mental retardation worldwide, according to the World Health Organisation. It may adversely affect brain maturation processes that potentially result in structural and metabolic brain abnormalities, visible on Magnetic Resonance (MR) techniques. Currently, however, there has been no review of the appearance of these brain changes on MR methods. Methods: A systematic review was conducted using 3 online search databases (Medline, Embase and Web of Knowledge) using multiple combinations of the following search terms: iodine, iodine deficiency, magnetic resonance, MRI, MRS, brain, imaging and iodine deficiency disorders (i.e. hypothyroxinaemia, congenital hypothyroidism, hypothyroidism and cretinism). Results: Up to May 2013, 1673 related papers were found. Of these, 29 studies confirmed their findings directly using MR Imaging and/or MR Spectroscopy. Of them, 28 were in humans and involved 157 subjects, 46 of whom had primary hypothyroidism, 97 had congenital hypothyroidism, 3 had endemic cretinism and 11 had subclinical hypothyroidism. The studies were small, with a mean relevant sample size of 6, median 2, range 1 -35, while 14 studies were individual case reports. T1-weighted was the most commonly used MRI sequence (20/29 studies) and 1.5 Tesla was the most commonly used magnet strength (6/10 studies that provided this information). Pituitary abnormalities (18/29 studies) and cerebellar atrophy (3/29 studies) were the most prevalent brain abnormalities found. Only fMRI studies (3/29) reported cognition-related abnormalities but the brain changes found were limited to a visual description in all studies. Conclusions: More studies that use MR methods to identify changes on brain volume or other global structural abnormalities and explain the mechanism of ID causing thyroid dysfunction and hence cognitive damage are required. Given the role of MR techniques in cognitive studies, this review provides a starting point for researching the macroscopic structural brain changes caused by ID.

Iodine as Essential Nutrient during the First 1000 Days of Life

“…Once the almost universal involvement of thyroid hormones in the development and proliferation of foetal neural tissue is recognised, it is not difficult to foresee the complex spectrum of neurologic disorders that can be associated with iodine deficiency at the early stages of intrauterine development. The permanent lesions of the cerebral cortex, hippocampus and cerebellum will offer relatively well-defined characteristics: lack of damage at the encephalic trunk or spinal cord will prevent direct motor symptoms, but motor coordination will be altered [ 60 ]; lesions will affect higher-order integrative cortical areas with a poorly defined anatomical basis, including silent areas of the associative cortex [ 61 ]; there will be no clinical expression during the perinatal period, with later onset of symptoms during infancy or school age [ 57 ]; such lesions can hardly be detected by the current techniques for prenatal diagnosis such as ultrasounds or foetal MRI [ 62 ]. …”

“…such lesions can hardly be detected by the current techniques for prenatal diagnosis such as ultrasounds or foetal MRI [ 62 ].…”

Does Withania somnifera mitigate the structural alterations of the rat brain associated with propylthiouracil?

“…A review of Hernández et al (32) reported contradictory opinions concerning the findings of imaging approaches in cases of thyroid dysfunction in both levels (human and experimental) and that due to the method used and the region examined. Regarding the microscopic evaluation, this work displayed that sections of rats which were submitted to PTU exhibited structural changes in cerebellar cortex indicating the adverse effect of this agent as it induces the thyroid dysfunction (33).…”

Factors associated with recent iodine intake level among household food handlers in Southwest Ethiopia: a cross-sectional study

“…Globally, an estimated 2 billion people are victims of IDD. Iodine deficiency (ID) is strongly linked to poor physical growth and significant cognitive capacity reduction in iodine deficient individuals [ 7 ]. Furthermore, more than five million children are victims of the severe form of IDD, accompanied by severe mental and physical growth deficits.…”