Thyroid hypertrophy

Northern bobwhite fed 5 mg/kg dietary toxaphene for 4 months showed thyroid hypertrophy (Pollock and Kilgore 1978) and interference with the ability of bobwhites to discriminate patterns (Kreitzer 1980). In the latter investigation, Kreitzer fed 10 or 50 mg/kg dietary toxaphene to 3-day-old bobwhites for 20 weeks and found that toxaphene-treated birds made 50% more errors than... 

Increased metabolism or elimination of the chemical by liver enzymes, such as occurs in rats when thyroid hormone ( , T4) elimination is enhanced, resulting in a compensatory increase in thyroid-stimulating hormone (TSH) and thyroid hypertrophy. 

Goats, sheep and cattle and their offspring receiving < 100 jg I kg feed DM developed a thyroid hypertrophy (goiter). In intrauterine iodine-depleted kids, the thyroid was enlarged to 40-fold that of control kids, while the thyroid of the mothers were increased 27-fold. Such increases also occurred, but to lesser degrees, in sheep and their lambs (15-fold) and in calves and fattening bulls (only 2- to 5-fold) (Table 9.4-23). 

An enlarged, palpable thyroid gland is referred to as a goiter. When insufficient thyroid hormone is liberated from the thyroid gland, the breakdown of the thyroid-pituitary-hypothalamic feedback mechanism results in the release of excess TSH and in the formation of a thyroid hypertrophy referred to as a nontoxic goiter. 

Ear, nose and throat, endocrine and gastrointestinal systems The safety of ginkgo biloba extract was investigated in rats and mice as part of a U.S. National Toxicology Program [9. Animals were administered com oil extract with or without ginkgo biloba, at different doses, for up to 2 years. Ginkgo biloba induced liver and thyroid hypertrophy in rats and mice liver hyperplasia in rats hyperplasia and atrophy of the epithelium in the nose of rats and inflammation, hyperplasia and ulcer in the stomach of mice. Moreover, there was an increased incidence of thyroid cancer in rats and male mice, and liver cancer in mice [9 ]. 

General Goiter Prevalence. The figure 1 shows the prevalence of goiter in the studied districts. With 16.7% of thyroid hypertrophy we can state a persistence of an endemic goiter area in France but there are only 3.9 % of clinically expressed goiters (fig.l). 

THOMAS G A, WILLIAMS E D (1999) Thyroid stimulating hormone (TSH)-associated follicular hypertrophy and hyperplasia as a mechanism of thyroid carcinogenesis in mice and rats. lARC Sci Publ. 147 45-59. 

Small doses of disulfiram reportedly can cause effects on thyroid iodine uptake and thyroid gland hypertrophy. It may also produce dermatitis and acneform rashes. 

Special risk patients Administer with caution to patients with thyroid disease, diabetes mellitus, cardiovascular disease, coronary artery disease, hypertension, peripheral vascular disease, heart disease, ischemic heart disease, increased intraocular pressure, or prostatic hypertrophy. 

Chronic inhalation exposure to 0, 75, 250 or 750 ppm [0, 0.32, 1.1 or 3.3 g/m ] ethylbenzene for 6 h per day on five days per week for 104 weeks caused an increased incidence of renal tubule h erplasia in male Fischer 344/N rats and increased severity of spontaneous, age-related chronic progressive nephropathy in males and females. Male B6C3Fi mice developed an increased incidence of alveolar epithelial metaplasia, syncytial alterations of hepatocytes, hepatocellular hypertrophy, hepatocyte necrosis and thyroid gland follicular-cell h erplasia. Exposure to ethylbenzene also caused an... 

Intermediate-duration oral studies in rats have shown that high doses of DEHP can affect thyroid cell structure (e g., hypertrophy of Golgi apparatus, increases in lysosomes, dilation of the endoplasmic reticula, and increase in colloid droplets) and function (e.g., decrease levels of circulating T4) (Hinton et al. 1986 Poon et al. 1997 Price et al. 1987, 1988a). When large oral doses of 500 and 2,500 mg/kg/day DEHP were combined with dietary exposure to a compound which has similar effects on the thyroid (Aroclor 1254, a polychlorinated biphenyl mixture), there was an apparent additive effect of the two compounds on changes in thyroid cell structure and decreases in serum T3 and T4. At lower doses of DEHP (50 and 100 mg/kg/day) and Aroclor 1254 there were no additive effects apparent with the changes in cell structure or the levels of T3 and T4. 

Iodine is a powerful oxidizing agent and has a direct action on cells by precipitating proteins. The affected cells may be destroyed. In addition to the primary irritant action of iodine, this compound can act as a potent sensitizer. Iodine is an integral part of thyroid hormones (tetraiodothyronine (thyroxine) and triiodothyronine), and deficiency results in compensatory hyperplasia and hypertrophy of the thyroid gland (endemic goiter). Endemic goiter occurs naturally where soil is deficient in iodine. 

In a subacute study, both male and female rats were fed diets containing octachlorostyrene at 0.5, 5.0, 50, and 500 mg kg for 28 days. Histological changes were observed in the liver and thyroid of rats exposed to doses equal to or greater than 5 mgkg. Hepatic microsomal enzyme induction and liver hypertrophy were observed in the two highest dose groups. At 500 mg kg there was an increase in... 

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