No description available.

PCBs are known to cause thyroid disruption in laboratory rats and are thought to be the causal agent in thyroid gland alterations in herring gulls in the Great Lakes. This study examined the regulation of thyroid hormone supply during development in (1) domestic chicken embryos (Gallus domesticus) exposed to a specific dioxin-like PCB congener (PCB-126) and (2) herring gull (Larus argentatus) embryos and pre-fledglings from Great Lakes sites with different chemical pollutant exposures. Specifically, PCB effects on thyroid status were evaluated by measuring plasma thyroid hormone concentrations and brain type II 5'D activity (to determine if PCB exposure was associated with alteration in brain 5'D type II activity that could maintain local T3 supply to the brain). If PCB-126 and PCB mixtures altered thyroid function, we expected to see decreased plasma thyroid hormone concentrations and subsequent increases in 5'D-II activity. Chicken eggs were injected (into the air cell) before incubation with five dose levels (0.0512, 0.128, 0.32, 0.64, 0.8 ng/g) of PCB-126 (3,3, 4,4',5-pentachlorobiphenyl), or vehicle (sunflower oil); sampling was on day 20 of the 21-day incubation period. Studies on PCB-treated embryos included a preliminary study and a larger study encompassing a serious of smaller studies. Herring gull embryos (at pipping, on day 25 of the 26 day incubation), and 28-day pre-fledgling chicks were sampled (for two field seasons) at several Great Lakes sites with different contaminant exposures (with Kent Island being the reference site). In PCB-treated chicken embryos, there were no statistically significant decreases in plasma T4 or T3 concentrations and no significant increases in brain 5'D-II activity in either the preliminary or the larger study. We found no clear pattern of altered thyroid function in herring gulls from polluted Great Lakes' sites. Plasma TH concentrations were not significantly decreased and 5'D-II activity did not significantly increase in birds from more contaminated sites in comparison to birds from Kent Island or sites with less contamination. Although pipped embryos from Strachnan Island had a significant increase in 5'D-II activity when compared to Kent Island, there were no differences in plasma TH concentrations, and brain 5'D-II activity was not significantly increased in birds from sites with greater PCB loads than Strachnan Island. Plasma T4 and T3 concentrations were significantly decreased in prefledglings from West Sister Island and Detroit Edison in comparison to Kent Island, but there was no subsequent increase in brain 5'D-II activity. The present study is the first to evaluate the potential effects of PCBs, alone and in a mixed environmental exposure, on circulating THs and brain 5'D-II activity in developing birds. Although thyroid function was not altered by the specific PCB congener used in my study or by exposure to environmental pollutants, more complete evaluations are needed before determining whether PCBs alter thyroid function in birds. / Master of Science

No description available.

The role of selected hormones in the control of hair follicle activity, fibre growth and moult in cashmere goats was investigated by manipulation of prolactin (PRL), thyroid hormones, and growth hormone (GH) individually or in combination. In experiment 1, the effect of different doses of the anti-thyroid drug "propylthiouracil" (PTU), on thyroxine (T4) and triiodothyronine (T3) profiles and deiodinase enzyme activities in liver, kidney and skin tissues was determined. Types II and III deiodinase enzymes were found to be present in goat skin but not type I. It was concluded that the supply of T3 within the skin was partly independent of circulating hormone profiles. In experiment 2, goats were treated with PTU, triiodothyronine (T3) and bromocriptine (Br) to decrease T3 availability to tissues and circulating PRL concentrations, respectively. Treatment with Br delayed the spring rise in plasma PRL concentrations (P=0.06) and primary (P<0.05) hair follicle activity, and delayed moult onset (P<0.01). PTU treatment did not significantly affect hair follicle activity but generally delayed the time of moult onset (P<0.05). The effects of the treatments were not additive, indicating that the actions of the two hormones were not independent. The effects of PTU and Br treatments were not exerted through changes in IGF-I binding activity in the skin, but binding was greater (P<0.01) in April than November. In experiment 3, treatment with bovine somatotropin (bST), T4 or metoclopramide to increase circulating concentrations of GH, T4 or PRL, failed to prolong the period of anagen in hair follicles, but bST increased fibre growth rate (P<0.05) and this was associated with higher circulating IGF-I concentrations. It is concluded that manipulation of the cycle of the cashmere-producing hair follicle is unlikely to be achieved through manipulation of circulating hormone concentrations alone and that much regulation of hair follicle activity occurs within the skin itself, possibly through changes in enzymes that control the supply of T3 to the follicles, in hormone receptor activity, and in the rate of synthesis of IGF-I and other growth factors within the skin.

A dissertation submitted to the Faculty of Medicine, University of the Witwatersrand, Johannesburg, in part fulfilment of the requirements for the degree Master of Medicine in Internal Medicine. 1993. / Normal thyroid physiology and pathophysiOlogy with reference to non-thyroidal illness is reviwed, including infections, specific disease states and drugs and their effects on thyroid function tests. A review of the literature reveals that following almost any infection the serum T4 and T3 decrease as a result of diminished secretion of TSH and thyroxine, accelerated T4 disappearance, inhibition of hormone binding to transport proteins and decreased peripheral T4 to T3 conversion. [Abbreviated Abstract. Open document to view full version] / AC2017

by Kareen Kar-lit Wong. / Thesis (M.Phil.)--The Chinese University of Hong Kong. / Bibliography: l. 134-146.

Orientador: Célia Regina Nogueira / Resumo: Os hormônios tireóideos, o estrógeno e outros hormônios atuam no crescimento e desenvolvimento do tecido mamário. Os receptores de estrógeno devem estar presentes para que o estrógeno possa atuar na atividade biológica das células mamárias. A presença ou ausência destes receptores no tecido tem influência direta na terapêutica e prognóstico clínico do câncer de mama. Os receptores do estrógeno e do hormônio tireóideo (T3) são membros da "superfamília de receptores" intracelulares. Estes receptores atuam na ativação da transcrição de genes alvo, através da união ao seu elemento responsivo hormonal. Ainda não se sabe de que forma o hormônio tireóideo atua no tecido tumoral mamário. Estudos epidemiológicos são contraditórios, mostrando que, quando os níveis de T3 estão elevados existe proteção contra o desenvolvimento de câncer de mama. Outros estudos demonstram haver aumento no risco e incidência do câncer mamário em pacientes hipertireoideas. Análises in vitro demonstraram que o T3, em concentrações suprafisiológicas induz a proliferação celular. Em pacientes com câncer de mama realizamos dosagens hormonais e verificamos a expressão dos receptores de estrógeno. Também foi estudada a conformação da molécula do T3 e do receptor de estrógeno, para confirmar se uma possível ligação estaria ocorrendo entre o T3 e o ER... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Thyroid hormones, estrogen and other hormones act in the growth and development of breast tissue. Estrogen receptors must be present so that estrogen can act in the biological activity of breast cells. The presence or the abscense of these receptors in tissue has direct influence on therapeutics and clinical prognostic of breast cancer. Estrogen and thyroid hormone (T3) receptors are members of intracellular "receptors superfamily". These receptors work in the activation of the transcription of target genes, linking them to their hormonal responsive. It is not known in which way thyroid hormone act in tumoral breast tissue. Epidemiologic studies are contradicting, showing that, when T3 levels are high, there is protection agains the development of breast cancer. Other studies show that there must be an increase in the risk and incidence of breast cancer in hyperthyroidean patients. In vitro analysis present that supra-physiologicals concentrations of T3 induces cellular proliferation. We performed hormonal dosage and verified the expression of estrogen receptors in breast cancer patients. The morphology of T3 molecule and of the estrogen receptor were also studied, to confirm if a possible link would exist between T3 and ER. Our results show an existance of a clinical relation between thyroid... (Complete abstract, click electronic access below) / Mestre

No description available.

Includes bibliographical references (leaves 191-207) / xiv, 207 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Examines the interactions between thyroid hormones and male reproductive function in mature, prepubertal and post pubertal Merino rams. Hypothyroidism or hyperthyroidism was induced in these rams for 8-10 weeks and their reprodroductive endocrine axis and testis functions were assessed. / Thesis (Ph.D.)--University of Adelaide, Dept. of Animal Sciences, 1986

Ph.D.