الفهرس 
causes of hypothyroidism
hypothalamusOnly 14 pages are availabe for public view
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Abstract
Thyroid hormones are recognized as key metabolic hormones that play a critical role in the CNS development throughout life. Thyroid hormones have marked effects on the growth, development and metabolic function of virtually all organs and tissues Normal brain development requires the presence of thyroid hormones that are essential for cell migration, dendrite and axon outgrowth, synapse formation, myelination and gliogenesis. It is now well established that the mammalian brain is a direct target organ of thyroid hormone, both during development and in adult individuals. Hypothyroidism refers to any state in which thyroid hormone production is below normal. Several reports are listed on the harmful effect of thyroid hormone deficiency during the development. Taken together, hypothyroidism can be classified based on its time of onset (congenital or acquired), severity (overt {clinical} or mild {subclinical}), and the degree of endocrine aberration (primary or secondary). Primary hypothyroidism follows a dysfunction of the thyroid gland itself, whereas secondary hypothyroidism results from the dysfunction of metabolic or messenger pathways associated with thyroid hormone production and metabolism. Primary hypothyroidism is characterized by reduced free thyroxine (FT4) levels and elevated TSH levels.