Iodine is required to form the hormone thyroxine. Thyroxine increases metobolic
rate by increasing cellular oxygen uptake and the burning of glucose to
150 mcg per day for adults age 11 and above. 175 mcg per day in pregnancy.
200 mcg during lactation.
studies have used iodine up to 3-6 gms per day.
Goiter is the classic severe iodine deficiency symptom. Goiter is characterized
by enlargement of the thyroid gland. The thyroid enlarges because the pituitary
hormone TSH (thyroid stimulating hormone) continues to stimulate the thyroid
to make more thyroxine when thyroxine levels are low. The thyroid cannot
make more thyroxine without iodine but it can continue to make the protein
component of thryoxine, thyroglobulin. With continued stimulation from TSH,
the thyroid overproduces thyroglobulin which accumulates in the thyroid
follicles. This accumulation of thyroglobulin causes the thyroid gland to
swell. Some 800,000,000 people worldwide suffer from iodine deficiency and
goiter. Goiter may be cured by administration of iodine. Iodine deficiency
may result in hypothyroidism. Prolonged hypothyroidism may develop into
myxedema, a condition characterized by fatigue, low body temperature, thinning
and loss of head hair - especially the loss of the lateral two thirds of
the eyebrows, apathy, drowsiness, slow speech, puffiness of the hands and
face, enlarged tongue and anemia. Iodine deficiency during pregnancy may
result in a form of physical and mental retardation known as cretinism in
the child. Iodine supplementation has produced relief of symptoms in some
women with fibrocystic breasts. Food sources Seafood including kelp and
other sea vegetables. Iodized salt. Lab tests Plasma iodine (by neutron
activation analysis, Urinary iodine
There is a wide margin of safety for the use of iodine. Dosages of 10 to
20 times normal have not produced ill effects though it is possible to produce
a form of enlarged thyroid gland from excessive iodine. Excessive iodine
intake inhibits the formation of thyroxine (thyroid hormone) because the
feedback mechanism to stimulate the production of thyroxine is a lack of
circulating iodine in the blood.
Iodized salt is the major source in the United States.
Works synergistically with the amino acid Tyrosine in forming thyroxine.
There are some plants that contain substances that inhibit the function
of thyroxine. These plants are called goitrogens. Some common foods containing
these substances are raw soybeans, peanuts, cabbage, cauliflower and turnips.
Cooking destroys goitrogens.
Iodine is absorbed
primarily from seafood and iodized salt. Dietary iodine is converted to
iodides and absorbed in the small intestine. The iodine transported through
the blood stream to the thyroid gland is bound with a protein complex
containing a large amount of the amino acid tyrosine. This complex is
called thyroglobulin. Approximately half the total body iodine is stored
in the muscles, 20% is contained in the thyroid gland, 10% in the skin,
6% in the bones and the rest is distributed throughout the other endocrine
glands, nervous system and blood. About a third of the iodine is retained
by the body. The rest is excreted in the urine within 2-3 days. The
retained iodine is converted to thyroxine by the thyroid gland. Iodine
is bound with plasma protein and transported to the cells as needed. The
hormone is eventually degraded in the liver and excreted in the bile.
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