Iodine in biology damage). In areas where there is little iodine in the diet, typically remote inland areas and semi-arid equatorial climates where no marine foods are eaten, iodine deficiency also gives rise to hypothyroidism, the most serious symptoms of which are epidemic goitre (swelling of the thyroid gland), extreme fatigue, mental slowing, depression, weight gain, and low basal body temperatures. The addition of iodine to table salt (so-called iodized salt) has largely eliminated the most severe consequences of iodine deficiency in wealthier nations, but deficiency remains a serious public health problem in the developing world. Iodine deficiency is also a problem in
Mitochondrial trifunctional protein deficiency mitochondrial trifunctional protein deficiency that may begin "after" infancy include hypotonia, muscle pain, a breakdown of muscle tissue, and a loss of sensation in the extremities called peripheral neuropathy. Some who have MTP deficiency show a progressive course associated with myopathy, and recurrent rhabdomyolysis. The genetics of mitochondrial trifunctional protein deficiency is based on mutations in the HADHA and HADHB genes which cause this disorder. These genes each provide instructions for making part of an enzyme complex called mitochondrial trifunctional protein. This enzyme complex functions in mitochondria, the energy-producing centers within cells: mitochondrial trifunctional protein contains three enzymes that each