Introduction
Hypothyroidism is a condition mainly characterized by low concentration of serum T4 (thyroxine) hormone. When this happen during pregnancy is known as maternal hypothyroxinemia. Adequate Thyroid hormone (T4) levels are critical during first trimester of gestation when the only source of T4 hormone of the fetus comes from the mother. A deficiency of T4 hormone constitutes a risk factor in the neurodevelopment and growth of the fetus . Severe mental retardation is one of the major conditions observed in children with non sufficient levels of thyroxine (T4) hormone during early fetal developing stages.
It is now well documented, that thyroid hormone deficiency lead to abnormal brain development especially in children. Those studies conducted to evaluate different periods of brain developments and the role of thyroid hormones on those stages of brain development. For instance, a study conducted by Kellyn (2011) on the effects of polybrominated diphenyl ether (PBDE) flame retardants on brain development found out that these retardants work majorly by interfering the function of the thyroid hormone receptor mediated transcriptions. This impairment influences the brain growth negatively.
This study uncover the impact of thyroid deficiency on the brain development during the perinatal period. Studies also shows that the complex treelike branching of purkinje cell dendrites which is very important to normal brain development is usually altered by the decreased level of thyroid hormone (Kellyn, 2011).
i .Effect of thyroid hormone on the developing brain
There are still some arguments in support of the uncertainties as to how thyroid hormone usually influences the maturation of the fetal brain. This relates to some of the unanswered questions regarding the maternal contribution specificity and the complete lack of knowledge that is related to the molecular targets of the thyroid hormones especially in the developing fetal brain (Morte et al, 2010). Although the arrays of clinical and epidemiological data on the influence of the hormone on the developing brain suggest otherwise.
Bernal (2007) showed the importance of the hormone in the development of the mammalian brain and how it acts on the migration and differentiation of neural cells which are very important to the brain. It also shows the synaptogenesis and myelination process which are all fundamental to brain development. According to this study, the action of the thyroid hormone is based on the mediation with nuclear thyroid hormone receptors stated earlier and the regulation of gene expression. An understanding of the impact of the thyroid hormone on the brain development shows that all environmental factors too that affects the thyroid will indirectly affect the brain development.
There are several other Thyroid receptor isoforms (TR isoforms) that are encoded by the THRA and THRB genes which are the genes expressed in the brain. These genes are responsible for the formation of TRalpha1 which is an important gene in the brain development. The study in rodents where the TRalpha1 was deleted gave an unfavorable consistent behavioral changes which if such happens in humans can be deleterious (Bernal, 2007).
Hypothyroidism usually results in several forms of structural defects on the developing brain. This relates with the increase in cell density of the cerebral cortex parts which is as a result of the reduction of the neurophil. It also leads to decrease number of the GABAergic interneurons that also relates to the cerebellum accumulating the neuronal precursors. These changes are the resultant effects of biological processes relating to deficient thyroid hormone level.
Since thyroid hormone is involved in the late events of the neural developments which entails the migration and terminal differentiation of neurons and glia, a problem with the level of the hormone will affects this morphological differentiation (Bernal, 2012). In most studies conducted, this morphological effects of reduced thyroid hormone are found to be related to the adult brain (Bernal, 2012).
The relationship of the topic with other systems of the body
The problem with the thyroid hormones adversely affects other systems of the body such as the muscle, heart, liver, kidney and developing brain (Umesh, 2007). This is simply because the protein synthesis the hormone is usually involved in becoming defected. Ability to promote the nitrogen retention and glycogenolysis is also affected negatively hence affects those organs that make use of such pathways.
Relationship with chiropractic
Chiropractors are people that practice chiropractic care which is a form of alternative medicine. This form of care is used to help manage patients with thyroid disorders especially with hypothyroidism. They basically involve in conditions that usually are not prescribed medication for.
Relationship with other basic science.
The basic relationship still relates more to that of the normal pathology. We need to understand that there are several causes of thyroid deficiencies but iodine deficiency seem to be the most important of all. The basic biology help describe the effect of iodine deficiency on the environment and the human body at large.
Conclusion
There are still several areas that needs to be uncovered so as to understand the full details of the impact of the hormone on the development of brain and the part of the brain that is mostly affected.
References
Bernal J. (2007). Thyroid hormone receptors in brain development and function.PubMed.
Retrieved 4 December, 2013 from http://www.ncbi.nlm.nih.gov/pubmed/17315033
Bernal, J. (2012). Thyroid Hormones in Brain Development and Function. Thyroid Disease Manager.
Retrieved 4 December, 2013 from http://www.thyroidmanager.org/chapter/thyroid-hormones-in-brain-development-and-function/#toc-translational-aspects
Kellyn, S.B. (2011). Thyroid Hormone Understanding Branches Out: Insights into PBDE Impacts on Brain Development. Environmental health perspective.
Retrieved 3 December, 2013 from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3040627/
Morte et al, (2010). Thyroid Hormone Regulation of Gene Expression in the Developing Rat Fetal Cerebral Cortex: Prominent Role of the Ca2+/Calmodulin-Dependent Protein Kinase IV Pathway
Retrieved 4 December, 2013 from http://endo.endojournals.org/content/151/2/810.long
Umesh, K. (2007). Health consequences of iodine deficiency.
Retrieved 4 December, 2013 from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3074887/
