Biofactors - Volume 19, issue 3-4

Article Type: Other

Citation: BioFactors, vol. 19, no. 3-4, pp. 101-105, 2003

Authors: Erdoǧan, Murat Faik

Article Type: Research Article

Abstract: Thiocyanate [SCN^- ] is a complex anion which is a potent inhibitor of iodide transport. It is the detoxification product of cyanide and can easily be measured in body fluids. Consumption of naturally occurring goitrogens, certain environmental toxins and cigarette smoke can significantly increase SCN^- concentrations to levels potentially capable of affecting the thyroid gland. Goiter endemics were reported to develop when the critical urinary iodine/ SCN^- …ratio decreases below 3 μg iodine per mg SCN^- . Iodine supplementation completely reverses the goitrogenic influence of SCN^- . SCN^- is also generated from cigarette smoking as a detoxifying product of cyanide. During the past two decades many reports dealt with the possible effects of cigarette smoking on thyroid hormone synthesis, thyroid gland size and thyroid autoimmunity including infiltrative ophtalmopathy of Graves' disease. In this mini-review, issues regarding thiocyanate overload and thyroid disease will be summarized. Show more

Keywords: thiocyanate, smoking, thyroid disorders, cassava

Citation: BioFactors, vol. 19, no. 3-4, pp. 107-111, 2003

Authors: van der Heide, Daan | Kastelijn, Jan | Schröder-van der Elst, Janny P.

Article Type: Research Article

Abstract: The most potent natural plant-derived compounds that can affect thyroid function, thyroid hormone secretion and availability to tissues is the group of flavonoids, i.e. plant pigments. They are present in our daily food, such as vegetables, fruits, grains, nuts, wine, and tea. Epidemiological studies suggest beneficial effects on health of flavonoids, which are commonly attributed to their activity as antioxidants. Experimental studies in vitro, however, showed inhibition of organification in thyroid cells and …follicles by several flavonoids. Studies in vivo and vitro with synthetic and natural flavonoids showed displacement of T_4 from transthyretin leading to disturbances in thyroid hormone availability in tissues. Radioactive labeled flavonoids appeared to be eliminated rapidly from the body mainly through excretion in the feces. In pregnant rats synthetic flavonoids cross the placenta and accumulate in the fetal compartment, including the fetal brain. Therefore, a high intake of flavonoids is contraindicated. In conclusion: flavonoids show strong interference with many aspects of thyroid hormone synthesis and availability. Show more

Keywords: flavonoids, thyroid hormone, fetal development

Citation: BioFactors, vol. 19, no. 3-4, pp. 113-119, 2003

Authors: Smyth, Peter P.A.

Article Type: Research Article

Abstract: The role played in thyroid hormonogenesis by iodide oxidation to iodine (organification) is well established. Iodine deficiency may produce conditions of oxidative stress with high TSH producing a level of H_2 O_2 , which because of lack of iodide is not being used to form thyroid hormones. The cytotoxic actions of excess iodide in thyroid cells may depend on the formation of free radicals and can be attributed to both necrotic and apoptotic mechanisms …with necrosis predominating in goiter development and apoptosis during iodide induced involution. These cytotoxic effects appear to depend on the status of antioxidative enzymes and may only be evident in conditions of selenium deficiency where the activity of selenium containing antioxidative enzymes is impaired. Less compelling evidence exists of a role for iodide as an antioxidant in the breast. However the Japanese experience may indicate a protective effect against breast cancer for an iodine rich seaweed containing diet. Similarly thyroid autoimmunity may also be associated with improved prognosis. Whether this phenomenon is breast specific and its possible relationship to iodine or selenium status awaits resolution. Show more

Keywords: antioxidant, thyroid, breast, iodine, thyroid antibodies

Citation: BioFactors, vol. 19, no. 3-4, pp. 121-130, 2003

Authors: Duntas, Leonidas H. | Orgiazzi, Jacques

Article Type: Research Article

Citation: BioFactors, vol. 19, no. 3-4, pp. 131-135, 2003

Authors: Chanoine, Jean-Pierre

Article Type: Research Article

Abstract: Selenium is an integral component of the enzymes glutathione peroxidase (GPx) and iodothyronine deiodinases. Although selenium nutrition could conceivably affect thyroid function in infants, children and adolescents, available data suggest that the effect of selenium deficiency on thyroid function is relatively modest. In patients with isolated selenium deficiency (such as patients with phenylketonuria receiving a low-protein diet), peripheral thyroid hormone metabolism is impaired but there are no changes in thyrotropin (TSH) or …clinical signs of hypothyroidism, suggesting that these patients are euthyroid. Selenium supplementation may be advisable to optimize tissue GPx activity and prevent potential oxidative stress damage. In areas where combined selenium and iodine deficiencies are present (such as endemic goiter areas in Central Africa), selenium deficiency may be responsible for the destruction of the thyroid gland in myxoedematous cretins but may also play a protective role by mitigating fetal hypothyroidism. In these areas, selenium supplementation should only be advocated at the same time or after iodine supplementation. In patients with absent or decreased production of thyroid hormones and who rely solely on deiodination of exogenous L-thyroxine for generation of the active triiodothyronine (such as patients with congenital hypothyroidism), selenium supplementation may optimize thyroid hormone feedback at the pituitary level and decrease stimulation of the residual thyroid tissue. Show more

Keywords: selenium, iodine deficiency, hypothyroidism, endemic cretinism, glutathione peroxidase, iodothyronine deiodinase, infants, children, adolescents

Citation: BioFactors, vol. 19, no. 3-4, pp. 137-143, 2003

Authors: Laurberg, Peter | Andersen, Stig | Pedersen, Inge Bülow | Ovesen, Lars | Knudsen, Nils

Article Type: Research Article

Abstract: Thyroid diseases are common in all populations but the type and frequency depends on environmental factors. In Denmark geographical differences in iodine intake are caused by different iodine contents of drinking water, which varies from < 1 to 139 μg iodine per litre. Comparative epidemiologic studies have demonstrated considerable differences in type and occurrence of thyroid disease with more goitre and hyperthyroidism in Aalborg with water iodine content around 5 μg/L, and more …hypothyroidism in Copenhagen with water iodine around 20 μg/L. In Denmark, iodine in ground water is bound in humic substances, which have probably leached from marine sediments in the aquifers. Interestingly, humic substances in water from other parts of the world have goitrogenic properties, especially humic substances from coal and shale. Humic substances are heterogeneous mixtures of naturally occurring molecules, produced by decomposition of plant and animal tissues. The effect of humic substances in drinking water on the epidemiology of thyroid disease probably depends on the source of aquifer sediments. Show more

Citation: BioFactors, vol. 19, no. 3-4, pp. 145-153, 2003

Authors: Bartalena, Luigi | Tanda, Maria Laura | Piantanida, Eliana | Lai, Adriana

Article Type: Research Article

Abstract: Graves' ophthalmopathy (GO) is a disorder of autoimmune origin caused by a complex interplay of endogenous and environmental factors. After recognition of one or more antigens shared by thyroid and orbit, activated T lymphocytes infiltrating the orbit trigger a cascade of events leading to production of cytokines, growth factors and oxygen reactive species. Proliferation of adipocytes and fibroblasts then follows, with an increased synthesis of glycosaminoglycans (GAG), which attract water and cause edema of …orbital structures and venous congestion. Proliferation of orbital fibroblasts and adipocytes, both in the retroocular tissue and in the perimysium of extraocular muscles, are among the most important events leading to the increased volume of orbital structures (fibroadipose tissue and extraocular muscles). The contribution of oxygen reactive species to the changes occurring in the orbit is underscored by in vitro studies. Superoxide radical stimulates orbital fibroblasts to proliferate and to produce GAG. Furthermore, hydrogen peroxide induces expression of HLA-DR and heat shock protein-72, involved in antigen recognition and T-lymphocyte recruitment. Cigarette smoking, which is probably the most important environmental factor associated with GO occurrence and maintenance, might also act, among other mechanisms, by enhancing generation of oxygen reactive species and reducing antioxidant production. Substances such as nicotinamide, allopurinol and pentoxifylline reduce superoxide- or hydrogen peroxide-induced proliferation of fibroblasts, GAG production and HLA-DR or HSP-72 expression by GO orbital fibroblasts, possibly through scavenging oxygen free radicals. Two small, non-randomized and/or uncontrolled studies investigated the effects of nicotinamide, allopurinol or pentoxifylline on GO. Favorable results were reported, but data are not fully convincing and the true effectiveness of these agents needs to be verified in randomized, controlled trials enrolling a larger number of patients.It currently seems unlikely that they may find a relevant place in the limited armamentarium available for the management of severe GO. Show more

Keywords: graves' ophthalmopathy, superoxide, hydrogen peroxide, pentoxifylline, nicotinamide, allopurinol

Citation: BioFactors, vol. 19, no. 3-4, pp. 155-163, 2003

Authors: Gärtner, Roland | Gasnier, Barbara C.H.

Article Type: Research Article

Abstract: We recently conducted a prospective, placebo-controlled clinical study, where we could demonstrate, that a substitution of 200 μg sodium selenite for three months in patients with autoimmune thyroiditis reduced thyroid peroxidase antibody (TPO-Ab) concentrations significantly. Forty-seven patients from the initially 70 patients agreed to participate in a follow-up cross-over study for further six months. One group (n = 13), which initially received selenium continued to take 200 μg sodium selenite (Se-Se), one …group stopped taking selenium (Se-0) ( n = 9), another group which received placebo started to take 200 μg selenium (n = 14) (Plac-Se) and the last group was without selenium substitution (Plac-0) (n = 11). TPO-Ab concentrations were measured at beginning and the end of the study. In the Se-Se group, the TPO-Ab concentrations further significantly p = 0.004) decreased from 625 ± 470 U/ml to 354 ± 321 U/ml, in the Se-0 group the TPO-Ab concentrations increased significantly p = 0.017) from 450 ± 335 to 708 ± 313 U/ml. In the placebo group, the TPO-Ab concentrations in those patients who were followed without selenium substitution were unchanged (1351 ± 940 vs. 1724 ± 1112 U/ml, p = 0.555). In contrast, the patients who received 200 μg sodium selenite after placebo, the TPO-Ab concentrations decreased significantly (p = 0.029) from 1182 ± 723 to 643 ± 477 U/ml. Show more

Keywords: autoimmune thyroiditis, selenium, thyroid peroxidase antibody, thyroglobulin antibody, clinical trial

Citation: BioFactors, vol. 19, no. 3-4, pp. 165-170, 2003

Authors: Schröder-van der Elst, Janny P. | Smit, Jan W.A. | Romijn, Hans A. | van der Heide, Daan

Article Type: Short Communication

Abstract: Flavonoids have inhibiting effects on the proliferation of cancer cells, including thyroidal ones. In the treatment of thyroid cancer the uptake of iodide is essential. Flavonoids are known to interfere with iodide organification in vitro, and to cause goiter. The influence of flavonoids on iodine metabolism was studied in a human thyroid cancer cell line (FTC-133) transfected with the human sodium/iodide transporter (NIS). All flavonoids inhibited growth, and iodide uptake was decreased in most cells. NIS …mRNA expression was affected during the early hours after treatment, indicating that these flavonoids can act on NIS. Pendrin mRNA expression did not change after treatment. Only myricetin increased iodide uptake. Apeginin, luteolin, kaempferol and F21388 increased the efflux of iodide, leading to a decreased retention of iodide. Instead myricetin increased the retention of iodide; this could be of use in the radioiodide treatment of thyroid cancer. Show more

Keywords: flavonoids, thyroid cancer, iodide uptake

Citation: BioFactors, vol. 19, no. 3-4, pp. 171-176, 2003