Thyroid total iodine

The LID fetuses developed goiter, and their thyroidal total iodine was 4.7 % of that of LID + I fetuses. The concentrations of T4 and T3 in different embryonic and fetal samples are shown in Figs. 8 and 9, where they are compared to data from age-paired samples obtained from C and T dams. Before onset of fetal thyroid function (11-day-old embryotrophoblasts and 17-day old fetuses) T4 concentrations are decreased by LID to a degree comparable to that of concepta taken from T mothers. T3 concentrations did not differ initially from those of the LID + I group. By 17 gd, however, T3 concentrations were lower both in the fetus, and placenta (not shown). Once fetal thyroid function starts, important differences become apparent between fetuses from T and LID dams. The activated secretion of T4 and T3 by the thyroid in fetuses from T mothers is able to compensate for previous differences related to maternal hypothyroidism, at least as far as the brain is concerned. But this is not possible for fetuses faced with a very low iodine supply, and cerebral T3 is quite low. Similar results were later obtained in another experimental series ... 

Thyrer thyrotrophin-releasing hormone, thyreotrophic hormone thyrotrophin. thyrocalcitonin calcitonin. a thyrocalcitonin calcitonin (pork), thyroglobulin [inn, usan] is obtained from thyroid glands of Sus scrota (hog), and contains >0.7% total iodine. It acts as a THYROID HORMONE, and was formerly used in the treatment of hypothyroidism. 

The availabihty of iodine varies geographically, and therefore, the size of the total iodine pool, as well as the concentration of iodine in the thyroid gland, can vary significantly depending on the access to iodine and on the thyroid size. Factors such as sex, age, and diet (that may... 

Thyroid types Concentration (yg/g) Total iodine (mg) n In vivo/in vitro References... 

Mission Number of subjects Mean days in space exposed to iodine (range) Total iodine exposure (mg) TSH reference range (pU/i) TSH prefiight annuai TSH prefiight TSH R + 0 TSH R + 3 TSH postflight annual Incidence of thyroid disease Comments... 

Surgical resection of the thyroid (total or near total thyroidectomy) followed by remnant ablation with radioactive iodine (RAI) therapy to destroy the remaining normal or cancerous thyroid tissue is considered the standard of care for all but small (less than 1—1.5 cm) thyroid cancers, and is associated with decreased frequency of local recurrences and an improvement in overall survival rate (Mazzafferi and Jhiang, 1994 Mazzafferi and Kloos, 2001). Furthermore, the elimination of uptake by residual normal thyroid tissue enhances the sensitivity of subsequent scanning and serum thyroglobufln (Tg) for detection of recurrent or persistent disease. 

In the thyroid follicular cell, intracellular iodide taken up from blood is bound in organic form in a few minutes, so less than 1 % of the total iodine of the gland is found as iodide. Therefore, inhibition of the iodide transport system requires blockade of organic binding. This can be achieved by the use of antithyroid drugs, of which n-propyl-6-thiouracil and 1-methyl-2-mercaptoimidazole (methimazole) are the most potent. 

Natural preparations include desiccated thyroid and thyrogiobuiin. Desiccated thyroid and thyrogiobuiin are derived from thyroid glands of domesticated animals that are used for food by human. The hormones were released from the proteolytic activity of gut enzymes. Potency is based on total iodine content or bioassay and is somewhat variable with different preparations. 

Interesting research into iodine content in human thyroids was also conducted by Zabala et al. (Zabala et al., 2009). Their study focuses on the determination of iodine content in healthy thyroid samples on male population from Caracas in Venezuela. The authors aimed at establishing a baseline of iodine content in thyroid glands and hence to comjjare the iodine thyroid concentration of the Venezuelan population with other countries. Male pxist-mortem individual samples were analyzed using a spectrophotometric flow injection method, based on the Sandell-Kolthoff reaction. The median intrathyroidal iodine concentration was 1443+/-677 pg/g (wet weight), ranging from 419 to 3430 pg/g, which corresponds to a median of total iodine content of 15+/-8 mg (ranging from 4 to 37). These results were... 

The metabolism of the thyroid gland can be investigated clinically by a number of different techniques such as studies on the concentration of iodine in blood, iodine excretion, thyroidal uptake of radioactive iodine, and determination of iodine in blood. The concentration of total iodine in blood is increased in hyperthyroid individuals. The increase is mainly in protein-bound iodine as it is determined in alcohol or zinc hydroxide precipitates. 

Although thyroid slices of hyperthyroid patients take up iodine more quickly than normal thyroid slices, the total iodine content of the thyroid gland (1.8 mg/g of dry weight in normal individuals) is consideraWy reduced in hyperthyroidism (0.26 mg/g of dry weight). The reduction affects both inorganic and organic iodine, but when all iodinated compounds in the thyroid are analyzed, thyroxine seems to be the compound most reduced in hyperthyroidism. 

Essential trace elements with their functions in enzymes and hormones are distributed in different parts of the body. Iodine is special. Some 75% of the total iodine content in the human body (about 14 mg) is found in the thyroid gland, a small organ in the neck. There, it participates in the formation of the important thyroid hormone, thyroxine. This is vital for normal mental and physical development and for regulating the body s metabolism. A recommended daily intake is 100-200 pg. Deficiency of iodine will cause goitre. This has to be treated by additional potassium iodide or iodine casein. In developed countries, iodine deficiencies are now rare because iodine is added to table salt. 

Iodine is found in the blood as inorganic and protein-bound iodine, the latter fraction probably representing the circulating thyroid hormone. The total iodine content of normal whole blood is about 8 to 12 /xg. per 100 ml. (range 3 to 30 /xg.) protein-bound iodine varies from 3 to 8 /xg. per 100 ml., with a mean of 5 to 6 /xg. (Chapter 22). The level of protein-bound iodine is increased in pregnancy and in hyperthyroidism and decreased in hypothyroidism. 

Despite the fact that a biological method is the only way to obtain a reliable estimate of the potency of thyroid, chemical assessment is still quite frequently required. The B.P, method is a determination of so-called iodine in combination as thyroxine and is based on the observations of Harington and Randall that, after hydrolysis of the thyroid with sodium hydroxide, an acid-insoluble fraction can be separated which consists essentially of thyroxine. There have always been mechanical difficulties associated with this assay, especially when an attempt is made to apply it to formulated products such as tablets. Further considerations, however, indicate that it is an unreliable guide to the potency of thyroid. Firstly, the discovery of the highly potent 3,5,3 -tri-iodothyronine (liothyronine) invalidates the assumption that the amount of total iodine in the acid-insoluble fraction is related to the proportion of thyroxine and hence to potency secondly it has been shown that when lactose is present during the hydrolysis stage a greater proportion of iodine is present in the subsequent acid-precipitated fraction than if the lactose is absent. This observation was first made by Doery and has since been confirmed in a... 

Tablets of Thyroid, B.P. Usually contain grain of thyroid. At present the only standardisation possible is by biological assay unless a sample of the thyroid used is available in the latter case for control purposes a total iodine content is satisfactory. Weigh and powder twenty tablets, or more if necessary, and carry out the assay described above under Thyroid using a weight of powder, not exceeding 0 4 g, equivalent to about 0 2 g of thyroid.

For humans, the effect of on thyroidal iodine metabolism can be similarly estimated. From the data of Blum and Eisenbud (1967), wherein was administered to suppress intake, and for a dietary intake of 150 mg d , the relationship of the 24-h uptake (Y) in percent, to the total iodine intake (X) in mg was computed to be... 

Gollnick DA, Greenfield MA. 1978. The in vivo measurement of the total iodine content of the thyroid gland by X-ray fluorescence. Radiology 126 197-200. 

In 40 patients we determined the mean iodine concentration as mentioned above. Additionally it was derived from the total iodine content of the gland, divided by the sonographically measured thyroid volume (Fig. 3). There was a good correlation with a coefficient of r = 0,9059, although the maximal error (95% of the cases) was as high as 36%, the mean error being + 15,2%. 

This observation concerns the imaging of the thyroid. When we pass from qualitative-semi-quantitative to purely quantitative evaluations there appears to be general agreement regarding the complete overlap of total iodine content values obtained with X-ray fluorescence in normal thyroids and those with various pathological conditions. 

The advantages of expressing the results of XRF measurements in mgl/gr thyroid tissue instead of total iodine have been extensively discussed by Leisner during the symposium held in Brussels in September 1982 and alluded to in Chapter VIII of this monograph. It seems nevertheless that from the point of view of clinical applications, the choice is essentially a question of available facilities Indeed, as a whole, comparable results in differential diagnosis and follow-up of patients have been obtained with both modes of expression.. An unexpensive approach such as described in Chapter IV might be a practical solution. 

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