Effect of Conjugated Equine Estrogens and Tamoxifen Administration on Thyroid Gland Histomorphology of the Rat

Abstract

OBJECTIVE: The aim of this study was to evaluate the action of the conjugated equine estrogens and tamoxifen on the morphology of thyroid gland in ovariectomized (OVx) rats. METHODS: Conjugated equine estrogens (CEE), clinically used as estrogen therapy, is a complex formulation containing multiple estrogens that decrease menopausal symptoms. Thirty ovariectomized rats were randomly divided into 3 treatment groups: GI, vehicle (propylene glycol); GII, CEE 200 µg/kg per day; and GIII, tamoxifen 1 mg/kg per day. Another group of 10 rats with intact ovaries (GIV) was included, treated with the vehicle, and sacrificed during estrous. All animals were treated by gavage for 50 days, after which they were sacrificed. Blood samples were collected, and the thyroid was removed for morphological analysis and PCNA evaluation through immunohistochemical study. RESULTS: The thyroid follicular cell height was increased in animals treated with CEE (14.90 ± 0.20 μm), with TAM (14.90 ± 0.10 μm), and in rats with intact ovaries (15.10 ± 0.50 μm) in comparison to that of the vehicle group (9.90 ± 0.20 μm) (P < 0.001). The follicular area was larger in the CEE (2,225 ± 51 μm 2) and TAM (2,127 ± 67 μm 2) groups compared to that of the vehicle group (5,016 ± 53 µm 2). The levels of T4 and T3 in rats treated with CEE, with Tamoxifen and in rats with intact ovaries, were higher than those those in the vehicle group (P < 0.001). The PCNA index in the vehicle group was lower than in other groups. CONCLUSION: Our data suggest that estrogen and tamoxifen administration has a proliferative effect on the thyroid.

Raloxifene effects on thyroid gland morphology in ovariectomized rats

“…In the present study, we show that raloxifene affects thyroid gland morphology of Ovx rats such as tamoxifen and estrogen do, as previously reported (8). We noted that ovariectomized rats treated with estrogen or raloxifene have increased thyrocytes height, and their follicular areas are normalized compared with sham-operated rats.…”

“…In a previous study, we have demonstrated that estrogen and tamoxifen both induce morphologic changes on thyroid glands of ovariectomized rats associated with changes in proliferating cell nuclear antigen (PCNA) immunoexpression (8). In the present study, our purpose was to evaluate the effects of raloxifene on thyroid gland morphology and PCNA analysis in ovariectomized rats, because this drug is used in the postmenopausal period.…”

Comparison Among the Daily Levothyroxine Doses According to the Etiology of Hypothyroidism

“…Although menopause does not bring marked changes in thyroid function, it nevertheless tends to reduce that function, especially when menopause occurs at the expected time [14]. Some studies have demonstrated influences of estrogens on the development, physiology, and pathology of the thyroid gland causing proliferation of thyroid tissue, which contains a large number of estrogen receptors [15]. However, it was shown that the effects of estrogen in the thyroid gland may be rather indirect, as a consequence of increased serum levels of thyroxin-binding globulin (TBG) in premenopausal women compared with those in menopause [12].…”

219 Supplementary Health Benefits of Linoleic Acid by Improvement of Vaginal Cornification of Ovariectomized Rats

“…Conjugated Equine Estrogen (0.625mg) was purchased from Wyeth, Montreal, Canada and prepared in a dosage of 0.2mg/kg [15][16][17] by dissolving it in distilled water, [13][14][15] and was used as a positive control for the purpose of comparison with the treated groups. All other reagents and chemicals were of analytical grade.…”