T3 ELISA

The triiodothyronine (T3), is a tyrosine-based
hormones produced by the thyroid gland. An
important component in the synthesis is iodine.
Thyroxine-binding globulin (TGB) is the major carrier
protein for circulating thyroid hormone. Only the free
fraction of T3 is biologically active, a very small
fraction of the circulating hormone is unbound - T3
0.3%.
The thyronines act on the body to increase the basal
metabolic rate, affect protein synthesis and increase
the body's sensitivity to catecholamines (such as
adrenaline) by permissiveness. The thyroid hormones
are essential to proper development and
differentiation of all cells of the human body. These
hormones also regulate protein, fat, and carbohydrate
metabolism, affecting how human cells use energetic
compounds. Numerous physiological and pathological
stimuli influence thyroid hormone synthesis.
Both excess and deficiency of thyroxine can cause
disorders. Thyrotoxicosis or hyperthyroidism is the
clinical syndrome caused by an excess of circulating
free thyroxine, free triiodothyronine, or both. It is a
common disorder that affects approximately 2% of
women and 0.2% of men. Hyperthyroidism is the case
where there is a deficiency of thyroxine.
Release of T3 from the thyroid gland into the blood is
~5-8 micrograms/day. In addition, approximately 22
mg/day of T3 is produced by nonthyroidal 5- monodeionination of T4. T3 has a much faster
turnover than T4 (T ~1 day, compared to ~6 days for
T4) and has greater biological potency than T4.
Several drugs are known to affect the binding of
Triiodothyronine to the thyroid hormone carrier
proteins or its metabolism to T3 and complicate the
interpretation of T3 results. Circulating autoantibodies
to T3 and hormone-binding inhibitors may interfere.
Measurement of total serum T3 concentrations is a
standard and well-validated test of thyroid gland
function.