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      Chronic Estradiol Exposure Modulates Thyroid Structure and Decreases T 4 and T 3 Serum Levels in Middle-Aged Female Rats

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          Objectives: In human medicine, estrogen is applied in prevention and treatment of health problems associated with the menopause. The aim of this study was to examine the effects of chronic estradiol dipropionate (EDP) treatment on thyroid gland structure and function in middle-aged female rats. Methods: At 14 months of age, Wistar rats received 0.625 mg EDP/kg b.w./day intraperitoneally for 2 weeks. The peripheral and central zones of the thyroid were stereologically analyzed and the following morphometric parameters determined: volume density of follicles, follicular epithelium, interstitium and colloid, epithelial height and the index of activation rate. Serum levels of TSH, T<sub>4</sub> and T<sub>3</sub> were determined by ELISA. Results: EDP treatment led to significant decreases in volume densities of follicles and follicular epithelium, epithelial height and index of activation rate (by 11%, p < 0.05; 23%, p < 0.005; 11%, p < 0.05 and 21%, p < 0.05, respectively) in comparison to control values. Hyperplasia of thyroid follicular cells was noticed in 25% of EDP-treated animals. Serum levels of T<sub>4</sub> and T<sub>3</sub> were decreased (by 33%, p < 0.005 and 28%, p < 0.001, respectively), but TSH concentration was not significantly different from that of the controls. Conclusion: Chronic estradiol treatment significantly decreased volume density and height of centrally located follicular epithelium, follicular activation index and serum level of total thyroid hormones in middle-aged rats.

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          Most cited references 9

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          Is Estradiol a Genotoxic Mutagenic Carcinogen?

           J G Liehr (2000)
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            Role of thyroid hormones in human and laboratory animal reproductive health.

            The highly conserved nature of the thyroid gland and the thyroid system among mammalian species suggests it is critical to species survival. Studies show the thyroid system plays a critical role in the development of several organ systems, including the reproductive tract. Despite its highly conserved nature, the thyroid system can have widely different effects on reproduction and reproductive tract development in different species. The present review focuses on assessing the role of thyroid hormones in human reproduction and reproductive tract development and comparing it to the role of thyroid hormones in laboratory animal reproduction and reproductive tract development. The review also assesses the effects of thyroid dysfunction on reproductive tract development and function in humans and laboratory animals. Consideration of such information is important in designing, conducting, and interpreting studies to assess the potential effects of thyroid toxicants on reproduction and development.
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              Expression of the estrogen receptor in human thyroid neoplasms.

              The expression and quantitation of the estrogen receptor (ER) in human thyroid tumors were examined by biochemical, immunohistochemical, and reverse transcriptase-polymerase chain reaction (RT-PCR) techniques. For this study, neoplasms, adenomatous goiters and adjacent normal thyroid tissues were obtained from 35 patients which included 10 cases of papillary carcinomas, 17 cases of adenomas and 8 cases of adenomatous goiters. Regardless of the histopathological subtype, ER was detected in 19% (5/27) of the neoplastic tissues with the mean value of ER content of 5.0 +/- 1.3 fmol/mg protein and the mean Kd value of 0.38 +/- 0.28 nM. ER was also detected, but at a lower concentration (2.8 +/- 1.6 fmol/mg protein), in the surrounding normal tissues. There was no significant difference between the neoplasms and adenomatous goiters with respect to the incidence of ER positivity and ER content. Furthermore, ER-positive specimens, as determined by both biochemical and immunohistochemical techniques, also showed the expression of ER mRNA detected by RT-PCR method. These results demonstrate that both ER mRNA as well as ER protein are expressed in thyroid neoplasms. This suggests the possibility that estrogen may affect the tumorigenesis or the progression of some thyroid neoplasms.

                Author and article information

                Horm Res Paediatr
                Hormone Research in Paediatrics
                S. Karger AG
                January 2005
                20 January 2005
                : 63
                : 1
                : 48-54
                aInstitute for Biological Research and bClinical Centre Dr Dragiša Mišović-Dedinje, Belgrade, Serbia & Montenegro
                83139 Horm Res 2005;63:48–54
                © 2005 S. Karger AG, Basel

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                Figures: 3, References: 32, Pages: 7
                Original Paper


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