Describe the symptoms of iodine deficiency.
What will be an ideal response?
When iodine availability decreases and plasma levels of T4 hormone drop, the pituitary gland secretes thyroid-stimulating hormone.
In response to increased TSH levels, the thyroid gland enlarges in an attempt to increase its efficiency at trapping iodine. The characteristic enlargement of the thyroid gland that occurs is called a goiter. This early adaptive response allows the thyroid gland to temporarily maintain thyroid hormone synthesis. Although a goiter is a painless condition, it can cause pressure on the esophagus and trachea and impair their function. If the underlying iodine deficiency is not corrected, decreased T4 synthesis, slowed metabolism, and more serious complications can develop.
Iodine deficiency is of particular concern during pregnancy because of the adverse effects it can have on the developing offspring. These include congenital abnormalities, low birth weight, neurological disorders, impaired mental function, poor physical development, and death. The resulting restriction of brain development and growth, called cretinism (Fig. 15-15), is characterized by severe mental retardation, loss of hearing and speech abilities, short stature, and muscle spasticity.
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