Thyroid nature

Brand Name(s) Armour Thyroid, Nature-Throid NT, Westhroid Chemical Class ENDO-thyroid hormone in natural state... 

Thirty isotopes are recognized. Only one stable isotope, 1271 is found in nature. The artificial radioisotope 1311, with a half-life of 8 days, has been used in treating the thyroid gland. The most common compounds are the iodides of sodium and potassium (KI) and the iodates (KIOs). Lack of iodine is the cause of goiter. 

In addition to the twenty amino acids commonly found in proteins, two others—selenocysteine and pyrrolysine—are found in some organisms, and more than 700 nonprotein amino acids are also found in nature. y-Amino-butyric acid (GABA), for instance, is found in the brain and acts as a neurotransmitter homocysteine is found in blood and is linked to coronary heart disease and thyroxine is found in the thyroid gland, where it acts as a hormone. 

Thyroid hormones used in medicine include both the natural and synthetic hormones. The synthetic hormones are generally preferred because they are more uniform in potency than are the natural hormones obtained from animals. Thyroid hormones are listed in the Summary Drug Table Thyroid and Antithyroid Dragp. 

Dal G, Carrasco L, Carrasco N Cloning and characterization of the thyroid iodide transporter. Nature 1996 379 458. 

Vasomotor symptoms, as well as other menopausal symptoms, occur in over 50% of perimenopausal women and over 80% of menopausal women.5 Menopausal symptoms tend to be more severe in women who undergo surgical menopause compared with natural menopause because of the more rapid decline in estrogen concentrations. Women who seek medical treatment should undergo laboratory evaluation to rule out other conditions that may present with similar symptoms, such as abnormal thyroid function or pituitary adenoma. Once other conditions have been excluded, HRT should be considered. 

An alternative therapeutic approach to osteoporosis is through the use of calcitonin (798), a peptide hormone containing 32 amino acids (the sequence is species dependent) secreted by the thyroid gland, which stimulates the production of new bone. Synthetic calcitonins corresponding to human, eel, and salmon variants, and natural calcitonin extracted from pig thyroid, are all used in medicine - they have slightly different efficacies, side effects, and tolerance levels (799). 

Hormonal actions occur during sensitive periods in development, in adult life during natural endocrine cycles and in response to experience as well as during the aging process (see Ch. 30). As a result of their fundamental actions on cellular processes and genomic activity and of the control of their secretion by environmental signals, steroid and thyroid hormone actions on the brain provide unique insights into the plasticity of the brain and behavior (see also Ch. 50). 

Excessive doses of thyroid hormone may lead to heart failure, angina pectoris, and myocardial infarction. Allergic or idiosyncratic reactions can occur with the natural animal-derived products such as desiccated thyroid and thyroglobulin, but they are extremely rare with the synthetic products used today. Excess exogenous thyroid hormone may reduce bone density and increase the risk of fracture. 

Such observations as these should inject caution into those who speak glibly about what metabolism is like in the mammalian organism. Furthermore, if differences such as these exist among different species of higher mammals, it lends credence to the idea that, within the human species, quantitative differences of a similar nature may exist. Because of differences in enzyme systems and the extent to which different metabolic pathways are utilized in different individuals, it is not at all unreasonable to conclude that different individuals probably have fundamental needs for quite different levels of the thyroid hormone. 

Phenylalanine (Phe or F) (2-amino-3-phenyl-propanoic acid) is a neutral, aromatic amino acid with the formula HOOCCH(NH2)CH2C6H5. It is classified as nonpolar because of the hydrophobic nature of the benzyl side chain. Tyr and Phe play a significant role not only in protein structure but also as important precursors for thyroid and adrenocortical hormones as well as in the synthesis of neurotransmitters such as dopamine and noradrenaline. The genetic disorder phenylketonuria (PKU) is the inability to metabolize Phe. This is caused by a deficiency of phenylalanine hydroxylase with the result that there is an accumulation of Phe in body fluids. Individuals with this disorder are known as phenylketonurics and must abstain from consumption of Phe. A nonfood source of Phe is the artificial sweetener aspartame (L-aspartyl-L-phenylalanine methyl ester), which is metabolized by the body into several by-products including Phe. The side chain of Phe is immune from side reactions, but during catalytic hydrogenations the aromatic ring can be saturated and converted into a hexahydrophenylalanine residue. ... 

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