Thyroid activity

Hyperthyroidism (thyrotoxicosis), defined as excessive thyroid activity, causes a state of thyroid hormone excess (thyrotoxicosis) characterized by an increased metabolic rate, increase in body temperature, sweating, tachycardia, tremor, nervousness, increased appetite and loss of weight. Common causes of hyperthyroidism are toxic multinodular goiter, toxic adenoma or diffuse toxic goitre ( Graves disease). Antithyroid diugs (methimazol, carbimazole, propylthiouracil) block thyroid hormone production and are hence suitable for the treatment of hyperthyroidism. 

MISCELLANEOUS ARYLALKANOIC ACIDS It has been known for some time that thyroxine, and related compounds such as liothyronine (88) are effective in lowering serum cholesterol. The normal metabolic activity of this class of thyroid active compounds has precluded their use as hypocholesterol-emic agents. 

FI. Pearson, H. A., and Druyan, R., Erythrocyte glucose-6-phosphate dehydrogenase activity related to thyroid activity. J. Lab. Clin. Med. 57, 343-349 (1961). 

Fairchild. E. J.. II. S. L. Graham. M. Hite. R. KUlens. and L. D. Scheel Granges in thyroid activity in ozone-tolerant and ozone-susceptible rats. Toxi col. Appl. Pharmacol. 6 607-613, 1964. 

Because of the negative feedback regulation of thyroid function, thyroid activation can be inhibited by administration of T4 doses equivalent to the endogenous daily output (approx. 150 pg/d). Deprived of stimulation, the inactive thyroid regresses in size. 

The Tier 2 testing assays are intended to confirm, characterize, and quantify effects for estrogen, androgen, and thyroid active substances. The EDSTAC selected Tier 2 to include the most sensitive developmental Ufestage, to identify the specific hazard caused by the chemical and establish a dose-response relationship, and to include a range of taxa. The Tier 2 screening assays under consideration by the US-EPA are summarized in Table 4.22. 

Abnormalities associated with primary and secondary sex organs, systemic hormone concentrations, and thyroid resulting from anti-androgenic and thyroid activity... 

Anti-thyroid activity. Pickled green olives, administered orally to adults at a dose of 200 g/person, were inactive on iodine uptake by the thyroid " . 

Thyroid activity. A freeze-dried aqueous extract of the leaf, administered to rats, was active. The results suggest a stimulatory action of the extract on the thyroid, unrelated to the pituitary° " ... 

Anti-thyroid activity. Boiled rice taken orally by adults at a dose of 350 g/person was inactive on iodine uptake by the thyroid Anti-tumor activity. Bran, administered intraperitoneally to mice at a dose of 100 mg/kg, was active on Sarcoma 180 (solid). The biological activity has been patented . Fermented grains, in the ration of rats, were active. Miso, a paste made from the seeds of Oryza sativa and G lycine max (soybean), was fed ad libitum. The incidence of cancers in the miso treated rats was 20% less than controls vs 7,12-dimethylbenz-[a]anthracene -induced carcinogenesis ". Water extract of dried seed hull, administered intraperitoneally to mice, was active on Sarcoma 180 (ASC). A glycoprotein fraction has been tested. The biological activity reported has been patented . Anti-ulcer activity. A cerebroside fraction of rice bran, administered intraperitoneally to mice at a dose of 100 mg/kg, was inac-... 

Lithium blocks the release of thyroid hormones, which are known to potentiate b-noradrenergic receptor sensitivity. This has led to the speculation that excessive thyroid activity may contribute to an episode of mania in susceptible patients, and that the antimanic effect of lithium is, at least in part, due to its antithyroid action (26). In this context, CBZ can also decrease various thyroid indices. 

Many of the manifestations of thyroid hyperactivity resemble sympathetic nervous system overactivity (especially in the cardiovascular system), although catecholamine levels are not increased. Changes in catecholamine-stimulated adenylyl cyclase activity as measured by cAMP are found with changes in thyroid activity. Possible explanations include increased numbers of 13 receptors or enhanced amplification of the 13 receptor signal. Other clinical symptoms reminiscent of excessive epinephrine activity (and partially alleviated by adrenoceptor antagonists) include lid lag and retraction, tremor, excessive sweating, anxiety, and nervousness. The opposite constellation of effects is seen in hypothyroidism (Table 38-4). 

Reduction of thyroid activity and hormone effects can be accomplished by agents that interfere with the production of thyroid hormones, by agents that modify the tissue response to thyroid hormones, or by glandular destruction with radiation or surgery. Goitrogens are agents that suppress secretion of T3 and T4 to subnormal levels and thereby increase TSH, which in... 

Noted Comments Significant stimulator of thyroid activity / suppression of thyroid function during use. 

E.V. Ivleva (1989a) found that, during the winter, Black Sea horse-mackerel displayed increased thyroid activity. This is directly related to the intensity of energy metabolism. Other workers found enhanced growth of the follicular cells of the thyroid gland of brown trout and brook trout during periods of low temperature (Woodhead and Woodhead, 1965a,b Drury and Eales, 1968), and increased thyroxine levels in the blood plasma (Eales et al, 1982). On the other hand, Leatherland (1994) has demonstrated a close positive correlation between water temperature and the concentrations of both forms of thyroid hormone (thyroxine and tri-iodothyronine) in the plasma of brown bullhead. 

In fresh water, salmon change from parr to smolt in preparation for the marine environment and this process involves increases in thyroid hormones (Boeuf, 1987). The thyroid activity of killifish in sea water is greater than that in fresh (McNabb and Pickford, 1970). However, in two species of... 

Drury, D.E. and Eales, J.G. (1968). The influence of temperature on histological and radiochemical measurements of thyroid activity in the eastern brook trout. Canadian Journal of Zoology 46,1-9. 

If vg is taken as 3 mm s-1, then a dosage of 1 Bqs m-3 of 131I in air gives 3 x 10-3 Bq m-2 fallout. The ratio of thyroid doses from milk compared with inhalation are then as shown in Table 3.9. The calculated ratio of 20 for adults compares with an increase of about 10 in the thyroid activity of Leeds residents attributed to consumption of milk in the days after the passage of the plume of activity from the Windscale accident (Fig. 3.7). The transfer factor fallout/milk in the Leeds area was lower than that assumed in the calculations leading to Table 3.8... 

After the Windscale and Chernobyl accidents, thyroid doses were calculated from measured thyroid activity in children and adults, assuming the mass of the thyroid to be appropriate to the age of the subject. In Table 3.10 the results for children are shown, and converted to the normalised dose per Bq m-2 deposition of 131I. Of the cases in Table 3.10, that at Leeds is the only one where the thyroid dose, normalised to unit deposition, approximates to the theoretical calculation of Table 3.8. 

Goldman JM, Laws SC, Balchak SK, Cooper RL, Kavlock RJ (2000) Endocrine-disrupting chemicals prepubertal exposures and effects on sexual maturation and thyroid activity in the female rat. A focus on the EDSTAC recommendations. Crit Rev Toxicol, 30 135-196. 

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