Thyroid extract/thyroxine

Thyroid extract/thyroxine Hormone Thyroid gland... 

Thyroxine is one of the few hormones for which unequivocal effects on isolated biochemical systems can be observed in particular, it has been shown that thyroxine at high concentrations has a direct effect on mitochondrial oxidation. Tissues from animals which have been injected with thyroid extracts or purified thyroxine show a raised oxygen consumption, particularly in liver and muscle. Similarly the addition of thyroxine to tissue slices of the same organs results in increased oxidation. Thyroxine seems to be especially trapped by the mitochondria, where it stimulates the... 

The only known metabolic role of iodine is in the synthesis of the thyroid hormones, thyroxine and triidothyronine. The thyroid of adult humans must trap about 60-65 pg I per day to provide adequate amounts of hormone. The normal human adult thyroid contains about 70 -80% of the total body stores of iodine (15-20 mg). The follicular cells extract iodine from the blood, with... 

In 1914, the major hormone of the thyroid gland, thyroxine, was isolated by Henry S. Plummer (1874-1936) of the Mayo Clinic. This was the second hormone to be isolated pure (adrenalin or epinephrine was isolated in 1901). Thyroxin-containing extracts, as well as the crystalline material, were successful in treatments of Graves disease ( goiter ). The chemical structure of thyroxin would be reported in 1926. 

In 1914, Kendall, a scientist at the Mayo Clinic in Minnesota, crystallized thyroxin, one of the thyroid hormones. The chemical structure of thyroxin wtis described in 1927 by Harrington and Barger, British university scientists. Harrington synthesized thyroxin, thereby paving the way for a more effective therapeutic agent than thyroid extracts which were variable in biological potency. 

Isoflavones have been implicated in goiter induction. Soybean extracts inhibit reactions catalyzed by thyroid peroxidase (TPO), essential to the synthesis of thyroid hormones (Divi et al., 1997). Genistein and daidzein (at about 1-10 p,M of IC50) may act as alternative substrates for tyrosine iodination (Divi et al., 1997). Furthermore, genistein and daidzein have also been shown to cause the irreversible inactivation of TPO in the presence of hydrogen peroxide. Genistein also inhibits thyroxine synthesis in the presence of iodinated... 

Bilberry extract 200 mg/(kg day) administered intraperitoneally to euthyroid rats increased radiolabeled triiodothyronine (T3) transport into the brain, compared to vehicle only (21). Postulated mechanisms include central or peripheral inhibition of L-thyroxine s (T4) deiodination to T3 inhibition of T3 protein binding or enhanced T3 binding to carrier proteins in the brain capillary wall (21). Whether bilberry could interact with thyroid replacement therapy remains to be seen. 

Gross, Leblond, Franklin, and Quastel (1950) have shown that rat thyroids contain small amounts of free iodinated amino acids which can be extracted with butanol from the thyroid without previous hydrolysis. These include monoiodotyrosine, diiodotyrosine, thyroxine, and triiodothyronine, and they are presumably formed by proteolysis of thyroglobulin. Their fate has been the subject of much experimental work in recent years. 

There has been much speculation in the past on the nature of the circulating thyroid hormone whether it was a simple amino acid, a peptide or polypeptide of thyroxine, or thyroglobulin itself. In 1948 Taurog and Chaikoff produced a considerable amount of evidence that the plasma hormone was indeed thyroxine. Labeled plasma iodine behaved chemically in a manner identical with that of thyroxine added to plasma it was nondialyzable it was precipitated with plasma proteins with zinc hydroxide it was extractable with butanol, and it could be fractionated with carrier thyroxine by its partition between immiscible solvents. This work received confirmation from Laidlaw (1949), and it then became generally accepted that thyroxine alone was the circulating hormone. 

Prior to the synthetic preparation of thyroxine, hypothyroidism was treated with extracts of dried thyroid glands from animals. Standardisation was however not easy, and the use of these nutritional supplements caused occasionally serious side-effects. Industrial manufacturing of the pure hormone began around 60 years ago. Its synthetic challenges consist in the formation of the diphenyl ether linkage and the iodination of the aromatic rings. [89]... 

The injection of moderate amounts of an anterior pituitary extract modifies the thyroid in such a way that it produces more thyroid hormones. Soon after injection, the gland grows, the cells enlarge and proliferate, iodine uptake is accelerated, and thyroglobulin synthesis and thyroxine release through proteolysis are increased. It now seems likely that all these effects result from the action of several hormones, some of which are still not known. 

A method of thyroid hormone estimation which consists of extracting iodinated amino acids from serum using n-butanol. The extract is washed with alkali which removes inorganic iodine and mono- and di-iodotyrosines, leaving behind triiodothyronine and thyroxine. The butanol extract can then by evaporated to dryness and analysed for iodide content. 

If thyrotropin were causing, or playing any part in, the bioassay responses measured with the injection of serum extracts, then it should be possible to remove that influence by the administration of thyrotropin-suppressing doses of thyroid hormone. To attempt this, thyroxine was injected for 8 days in a dose of 100 g every... 

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