The chemical purity of the iodine
in our Iodine is greater than or = 99.8%. We are
more concerned about the purity than the actual
source. Iodine from seaweed may possibly contain
impurities found in the ocean such as arsenic, bromine
in quantities that are not desirable or healthy.
Iodine Metabolism In the
The major function of the gland
is to concentrate iodine, and to synthesize thyroxine
(T 4 ) or triiodothyronine (T 3 ). There is always
about 20-50 mg of iodine in the body; 8 mg is in
the thyroid. The supply may be variable. Iodine
comes from water and food, but is also absorbed
by intact skin and lungs. Throughout the world,
the intake varies. 1 mg is needed per week, or about
50 mg/year. Diet under normal circumstances contains
at least 150 micrograms daily.
The iodine pump (iodide trapping)
gets the ion into the thyroid. It works against
the concentration gradient which is at least 1 (blood)
to 25 (gland). The pump is activated by pituitary
TSH. ATP is utilized as a source of energy. Excess
iodine in the gland inhibits the thyroid hormone
Thyroid Hormone Synthesis
Iodide is first oxidized either
into nascent iodine Io or I 3- The enzyme peroxidase
is necessary as well as hydrogen peroxide. Then,
iodine is attached to tyrosine which is the precursor
of the thyroid hormones. Monoiodotyrosine and diiodotyrosine
are formed by tyrosine iodinase.
Then, two molecules of iodinated
tyrosine are coupled into T 3 and T 4 . T 3 is four
times as potent as T 4 . About three quarters of
the iodinated tyrosine never becomes thyroid hormones.
They may be released from thyroglobulin and deiodinated
by a deiodinase enzyme. About 90% of hormone produced
is thyroxin. The hormones are formed within a globulin
molecule in the thyroid and stored as thyroglobuline
(MW about 670,000), where there are about 3 molecules
of thyroxine and 1 molecule of T 3 per molecule
of thyroglobulin. About 2 to 3 months of supply
is stored in the gland.
Hormone release and transport
Thyroid hormone secretory pathway
is composed of three steps:
* The internalization and intracellular
transport of thyroglobulin,
* Proteolytic processing of the prohormone,
* Cellular handling and release of T 4 and T 3 .