No / In addition to their role in cellular metabolic activity, thyroid hormones (THs), also regulate neural development; the central nervous system is particularly dependent on TH for normal maturation and function. Specifically, there appears to be extensive inter-reliance between TH and acetylcholine (Ach), nerve growth factor and hippocampal function. These associations led us to investigate the possible effects of thyroxine (L-T4) on performance of a spatial learning task, where cholinergic activity and hippocampal function are known to be important. Groups of rats (n=20) received saline (controls) or L-T4 at 2.5 or 5 mg/kg daily for 4 days as a sub-chronic treatment, or 0, 5 or 10 mg/kg doses administered every third day for 28 days prior to testing as a chronic regimen. Rats were assessed in a watermaze for their ability to find a submerged or visible platform. Forty minutes prior to watermaze testing, half the animals in each group received 1 mg/kg scopolamine to elicit a cognitive deficit. Following testing, rats were decapitated, blood samples taken, and the frontal cortex and hippocampus were dissected out for acetylcholinesterase (AChE) assay. The results showed that L-T4 treatment, administered both sub-chronically and chronically, significantly enhanced the ability of rats to learn a spatial memory task, compared with controls. Moreover, both short-term and long-term L-T4 treatment reduced the cognitive-impairing effects of scopolamine. Improvements in performance were shown to occur alongside significantly increased cholinergic activity in frontal cortex and in the hippocampus of treated animals.These findings demonstrate an augmentative effect of L-T4 upon cognitive function, possibly mediated by an enhancement of cholinergic activity. The results support previous findings of a relationship between L-T4 and acetylcholine, and underscore possible mechanisms by which disorders of thyroid function may be associated with cognitive decline.

Thyroid hormone content in eggs varies with the thyroid status of the hen and may influence embryonic development prior to the release of appreciable amounts of thyroid hormones by the embryonic thyroid gland. Methods for the measurement of thyroid hormones in egg yolk were verified by demonstrating consistency in the recovery of yolk thyroid hormones following a methanol/chloroform extraction, and in the measurement of thyroid hormones in extracts across a range of dilutions by RIA. Untreated hens produced eggs with yolk T₄ that was low relative to plasma T₄, but yolk T₃ that was comparable to plasma T₃. Hens dosed twice daily with L-thyroxine (T₄; 1x or 3x the daily thyroid secretion rate of T₄ per dose) showed significant increases in T₄ concentrations in their plasma and in the yolk of their eggs. Maternal thyroid hormone deposition in yolk varied with hens’ thyroid status. T₄ dosed hens demonstrated “levels” of hyperthyroidism and deposited greater amounts of T₄ into egg yolk compared to controls, yet appeared to regulate T₄ deposition into egg yolk at each level. Pelvic cartilage, a thyroid hormone responsive tissue, showed enhanced growth and differentiation in embryos from eggs of hens given the highest dose of T₄. Specifically, alkaline phosphatase activity (a marker of differentiation) and pelvic cartilage weights were significantly greater in embryos from high T₄ eggs than in controls. However, chicks from high T₄ eggs did not have measurable differences in total thyroid hormone content (carcass without the thyroid gland), general body growth (body weight, length, and general morphology), or hatchability when compared to controls. / Master of Science

Sixty-two newborn Holstein-Friesian calves were used to study the role of colostrokinin, serum cortisol, and serum thyroxine in the absorption of maternal immunoglobulin. Calves were removed from their dams prior to suckling and assigned one of four rations: colostrum, whole milk, milk plus colostral immunoglobulin, and milk plus immunoglobulin plus colostrokinin. Calves were fed their assigned ration either at birth or after twelve hours inanition. All calves were fed pooled colostrum at 24 hours postpartum. Blood samples were collected at seventeen times during the first 32 hours postpartum. Calves were born with high cortisol concentrations (88 ng/ml) which decreased (P < .05) within two hours postfeeding. Serum cortisol levels increased (P < .05) between two and three hours after calves ingested a colostral source of immunoglobulin. Time of initial feeding had no effect on the cortisol surge. No such increase was observed in neonates consuming an immunoglobulin-free milk ration. These results demonstrate that the immunoglobulin fraction of colostrum is responsible for initiating an increase in cortisol secretion by the adrenal cortex. Within four hours postpartum, serum thyroxine concentrations increased (P < .05) at least 50% in all treatment groups regardless of whether the calves were fed or fasted. After peaking at 18 μg/dL, the serum thyroxine concentrations fell gradually throughout the duration of the collection period. Colostrokinin exhibited a biphasic effect on serum immunoglobulin concentrations which was dependent on the initial time of feeding. Calves exposed to colostrokinin in 0 hour feedings had serum immunoglobulin G concentrations significantly higher (P < .05) after 16 hours postpartum than animals not fed colostrokinin. Fasted calves, exposed to colostrokinin at 12 hours postpartum, had no increase in serum immunoglobulin G concentrations following a colostrum feeding at 24 hours postpartum. Fasted calves fed a ration not containing colostrokinin exhibited a two-fold increase in serum immunoglobulin G concentrations after the 24 hour colostrum feeding. Colostrokinin did not have an immediate effect on serum immunoglobulin G concentrations, but required an approximate twelve hour period to manifest its regulatory function. The presence or absence of colostrokinin in the experimental rations did not have any effect on the cortisol or thyroxine profiles. The variable serum immunoglobulin G profiles suggest that colostrokinin is involved in the acquisition of passive immunity by the calf, but colostrokinin may have more than one physiological role.

As doenças neuromusculares são um grupo heterogêneo de doenças genéticas, causadas por mutações nos genes codificando proteínas musculares sarcolemicas, sarcoméricas, e citosolicas. A Distrofia Muscular de Duchenne (DMD) é uma miopatia degenerativa progressiva, caracterizada pela ausência da proteína distrofina na superfície da membrana da célula muscular. O modelo de cão Golden Retriever Muscular Dystrophy (GRMD) apresenta semelhanças clínicas de DMD devido ao seu tamanho maior e significativa fraqueza muscular, é geneticamente homólogo a DMD humana, sendo considerado modelo experimental para estudos de novas propostas terapêuticas e melhor entendimento da fisiopatogenia da doença. Não existe até o momento uma terapia efetiva em bloquear ou reverter o processo da distrofia muscular. Embora a terapia gênica e o transplante de células tronco possam fornecer a cura para a DMD, resultados positivos podem demorar algum tempo até serem clinicamente viáveis. Neste sentido, a busca de informações fisiopatológicas que podem estar correlacionadas com a distrofia, e, com o avanço da pesquisa há possibilidade de melhora na condição vital do paciente, por retardo da progressão dos sinais clínicos ou cura. Existem poucos estudos endócrinos em animais portadores de distrofia como aves, GRMD e o mdx, assim como no homem. Mediante a falta de dados, houve a necessidade de quantificar e comparar hormônios, ainda não analisados, assim como avaliar a morfologia de glândulas endócrinas no modelo experimental GRMD. Para que fosse possível a correlação na interferência hormonal na evolução da Distrofia Muscular do cão, os exames sanguíneos foram comparados com cães normais e com as portadoras, todos da raça Golden Retriever. A mensuração hormonal de triiodotironina total (T3T), tiroxina total (T4T), a tireotropina (TSH) e o cortisol foram processados através de \"kits\" comerciais para radioimunoensaio, e o tiroxina livre (T4L) com \"kit\" comercial por diálise. As análises morfológicas das adrenais e da tireóide foram feitas através da macroscopia, microscopia de luz e microscopia eletrônica de transmissão de materiais de GRMD e de cães sadios. Anatomica e morfológicamente as glândulas não apresentaram alterações. Os níveis de cortisol não variaram significantemente entre os grupos estudados. Os níveis de T3 total foi semelhante para os animais sadios, portadoras e afetados. T4 total apresentou-se em diferentes níveis em alguns grupos. O T4 livre não variou significantemente entre os grupos estudados. Os níveis séricos de TSH da maioria dos Golden Retriever, afetados, portadores e sadios, apresentaram-se abaixo do limite apresentado pelos valores de referência. / Neuromuscular diseases are a heterogeneous group of genetic diseases caused by mutations in genes encoding proteins muscle sarcolemma, sarcomeric, and cytosol. Duchenne Muscular Dystrophy (DMD) is a progressive degenerative myopathy characterized by absence of dystrophin on the surface membrane of muscle cells. The Golden Retriever Muscular Dystrophy (GRMD) shows clinical similarities of DMD due to its size and significant muscle weakness, is genetically homologous to human DMD, and is considered an experimental model for studies of new therapeutic approaches and better understanding of the pathogenesis of the disease.There is not an effective therapy to block or reverse the process of muscular dystrophy yet. Although gene therapy and stem cell transplantation may provide a cure for DMD, positive results may take some time to be clinically viable.In this sense, the search for pathologic and physiologic information can be correlated with muscular dystrophy, and with the advancement of research there is room for improvement in the vital condition of the patient by delaying the progression of clinical signs or cure.There are a few studies in animals with endocrine dystrophy such as birds, and GRMD mdx as well as in man. By lack of data, there was a need to quantify and compare hormones, not yet analyzed, as well as evaluating the morphology of endocrine glands in experimental model GRMD. To make possible the hormonal correlation in the evolution of muscular dystrophy in dogs, blood tests were compared with normal dogs and carriers, all Golden Retrievers. Measurement of total triiodothyronine hormone (T3T), total thyroxine (T4T), the thyrotropin (TSH) and cortisol were processed using commercial kits for radioimmunoassay, and free thyroxine (FT4) with commercial kit by dialysis.The morphological analysis of adrenal and thyroid were made by macroscopic, light microscopy and transmission electron microscopy of materials GRMD and healthy dogs. Anatomical and morphological glands were unaffected. Cortisol levels did not differ significantly between groups. The levels of total T3 was similar to the healthy animals, carriers and affected. The T4 presented at different levels in some groups. The free T4 did not differ significantly between groups. Serum TSH of most Golden Retriever, affected patients and healthy individuals, were below the limit presented by the reference values.

O objetivou-se com este trabalho foi avaliar a influência de óleos funcionais e monensina na dieta de vacas no verão sobre o consumo de matéria seca, parâmetros produtivos, sanguíneos, fisiológicos e hormonais, fermentação ruminal e a digestibilidade aparente total dos nutrientes. O projeto foi conduzido no Centro de Análise e Pesquisa Tecnológica do Agronegócio (APTA), no setor de Bovinos de Leite, Instituto de Zootecnia, Nova Odessa, SP. Foram utilizadas oito vacas da raça Holandesa primíparas, lactantes (68 ± 3,46 dias de lactação e 511,56 ± 65,38 pesos vivos), distribuídas em dois quadrados latinos contemporâneos, em arranjo fatorial 2x2, ou seja, dieta sem inclusão de aditivo, dieta com inclusão de óleo funcional (OF, 0,5 g/kg MS), dieta com inclusão de monensina (MO, 30 mg/kg MS) e dieta com inclusão de óleo funcional e monensina, nas mesmas quantidades já descritas. As vacas foram mantidas a temperatura média de 25,31°C ± 0,26; umidade relativa do ar de 71,24% ± 1,03 e índice de temperatura e umidade de 73,85 ± 0,14. No presente experimento não observou interação entre os tratamentos, porém os animais com OF apresentaram maior CMS e a inclusão de MO diminuiu esse parâmetro. Se tratando dos parâmetros fermentativos, a inclusão de MO aumentou a concentração de propionato e isovalérico, consecutivamente sua proporção e diminuiu a relação acético: propiônico, OF não alterou a fermentação ruminal. Os parâmetros bioquímicos apresentaram interação na quantidade de ácidos graxos não esterificados (NEFA), sendo que, a não inclusão de aditivos foi maior sua concentração do que a inclusão de ambos os aditivos. Quando se tratando da digestibilidade dos nutrientes, não houve diferença significativa para nenhuma das frações. Para aos parâmetros produtivos, a produção de leite, produção de leite corrigida para 3,5% de gordura e quantidade de gordura ocorreu interação entre os tratamentos, onde a dieta com OF na ausência de monensina aumentou esses parâmetros e quando incluído MO diminuiu. Já dieta com somente MO funcional diminuiu, os mesmos parâmetros, e a presença dos dois aditivos aumentou. A quantidade de lactose, proteína e o teor de proteína foram maiores para o tratamento incluído OF. A inclusão de MO diminuiu os teores de gordura e sólidos totais, porém esse tratamento apresentou maior eficiência produtiva. Nos parâmetros fisiológicos a quantidade de tiroxina (T4), e frequência respiratória (FR) também foi maior quando incluído OF comparado sem inclusão de aditivos. Já os demais parâmetros fisiológicos e hormonais (temperatura retal e do pelame e triiodotironina, T3) não foram afetados. O óleo funcional demonstrou eficácia em melhorar a produção de leite e consumo em animais submetidos a estresse calórico crônico sem alterar a fermentação ruminal e digestibilidade, porém aumentou a FR e o T4. Entretanto, a monensina foi capaz de alterar a fermentação sem alterar o consumo e os parâmetros fisiológicos e hormonais, também sendo mais eficiente produtivamente. / The objective of this work was to evaluate the influence of functional oils and monensin in the diet of cows submitted in the summer on dry matter intake, and how this influence affected their blood as well as their productive, physiological and hormonal parameters, ruminal fermentation and apparent digestibility of feed. The project was conducted in the Milk Cattle Sector at the Agribusiness Technological Research and Analysis Center (APTA), Institute of Animal Science, Nova Odessa, SP. Eight primiparous, lactating Holstein cows (68 ± 3.46 days of lactation and 511.56 ± 65.38 live weights) were used and distributed in two contemporary Latin squares, in a 2x2 factorial arrangement. They received four diets one without the inclusion of additives, one with functional oil (OF, 0.5 g / kg DM), one with monensin (MO, 30 mg / kg DM), and one with both functional oil and monensin with the same quantities as described. The cows were submitted to a mean temperature of 25.31°C ± 0.26 with a relative humidity of 71.24% ± 1.03 and a temperature and humidity index of 73.85 ± 0.14. In the present experiment, there was no interaction between the treatments, but the animals with + OF presented higher CMS and + MO decrease this parameter. When treating the fermentation parameters with MO, there was an increase in the amount of propionate and isovaleric, however, a decrease in the acetic: propionic ratio occurred. At the same time, only the proportion of propionate increased when treated with MO while isovaleric and acetic proportions remained the same, and the inclusion of OF did not alter the ruminal fermentation. The biochemical parameters showed interaction in the amount of non-esterified fatty acids (NEFA), and the without additives the concentration of NEFA was higher than with the inclusion of both additives. When it came to nutrient digestibility, there was no significant difference for any of the fractions. Regarding the productive parameters concerning milk production, this adjusted to 3.5% fat and the amount of fat experienced interaction between treatments of OF and MO; the diet with OF in the absence of monensin saw an increase in these productive parameters and when MO was included, a decrease occurred. The diet with only functional MO saw a decrease in the productive parameters, while this increased in the presence of both additives. The amount of lactose, protein, and protein content were higher in the treatments including OF. The inclusion of MO decreased the total fat and solid contents, but this treatment presented a higher productive efficiency. In the physiologic parameters the thyroxin (T4). The respiratory rate (RR) was also higher when including OF in comparison without additives, while the other physiological and hormonal parameters (rectal temperature, skin and triiodothyronine, T3) were not affected. Functional oil showed efficacy in improving milk production and consumption in animals submitted to chronic caloric stress without altering rumen fermentation and digestibility, but increased RF and T4. However, monensin was able to alter the fermentation without altering the consumption and the physiological and hormonal parameters, also being more efficient productively.

The objectives of this study are to characterize two carrier proteins in the horse that significantly decrease in humans following anabolic androgenic steroid administration: sex hormone-binding globulin (SHBG) and thyroxine-binding globulin (TBG). For SHBG characterization, qPCR, RNA sequencing, and immunohistochemistry were performed on testes and equine livers. Free and total testosterone immunoassays were utilized to confirm the presence of a carrier protein in equine circulation. SHBG was detected in the testes using qPCR, RNA sequencing, and IHC, indicating the presence of the isoform androgen-binding protein (ABP). SHBG was not detected in any liver samples. Evidence of a carrier protein was shown by free testosterone being significantly lower than the total testosterone that was detected in stallions (p < 0.0001) and pregnant mares (p < 0.0001). TBG characterization was completed using an equine specific TBG ELISA. Equine serum was analyzed across seasons, reproductive statuses, sexes, and ages. TBG concentrations were also measured following anabolic steroid administration (Stanozolol) and increased endogenous androgen production via hCG administration in stallions and aromatase inhibition via Letrozole administration in pregnant mares. TBG did not significantly differ across season, reproductive status, sex, or age Alterations of androgen concentrations did not result in any significant changes to circulating TBG concentrations.

Background: Paraben exposure occurs everyday to most people unknowingly. Parabens are present in most personal care products in varying amounts. Presently, parabens are not listed as endocrine disruptors; however, some research has shown parabens associated with decreases in thyroid hormone levels. The chemical and adsorption mechanism for parabens in association with thyroid hormones is not well understood. Determining whether parabens are associated with a change in thyroid hormone levels can help reduce the incidence of possible adverse health effects with exposure to parabens. Methodology: The selected study variables were analyzed using SAS version 9.2. Data were obtained from the 2007-2008 National Health and Nutrition Examination Survey (NHANES). Analyses were performed separately for adolescent females (12-19) and adult females (20+). Weighted means were performed for the main independent and dependent variables of interest stratified by race/ethnicity groups and by smoking status. Independent samples t-test and ANOVA was used to test significance of differences of weighted means. Weighted bivariate linear regression was performed for each dependent variable (Thyroid Stimulating Hormone [TSH], Triiodothyronine [T3], and Thyroxine [T4]) regressed on butylparaben. Weighted multiple linear regressions were performed and parameter estimates with 95% confidence intervals were used to ascertain the measure of effect. Separate regression models stratified by age group (adolescent vs. adult) were ran for each dependent variable (TSH, T3, and T4) regressed on butylparaben level and covariates, race/ethnicity and smoking status (ever smoked). Results: Weighted bivariate linear regression showed that among adult females, for each ng/ml increase in butylparaben, there was a -1.07 decrease in ng/dL T3 (p Weighted multiple linear regression showed higher butylparaben levels among adult females were associated with 0.12 ug/dL lower than average T4 levels (p Conclusion: While parabens are currently not considered endocrine disruptors, the human metabolism of and effects from exposure to parabens are not well understood. Results from this study showing decreased levels of some thyroid hormone levels (TSH, T3, and T4) associated with increased levels of butylparaben was found, as well as differences in thyroid hormone levels among racial/ethnic groups. Although not many human studies have found significant results, 10 some rodent studies have found butylparaben associations with thyroid hormone changes.4, 6, 19, 54 The results of this study indicating no statistically significant association between butylparaben and decreases in thyroid hormone levels are consistent with results of some rodent studies.7, 8, 54, 55 In light of these findings, additional human studies with paraben exposure and thyroid hormone levels are needed to increase knowledge of the mechanism and effect of parabens in the human body.

Metabolic depression is a ubiquitous characteristic of dormancy, allowing animals to survive off limited endogenous fuels supplies for extended periods of time. Metabolic depression is characterised by a complex set of physiological and biochemical changes (respiratory depression, bradycardia, hypophagia and cessation of renal function), in addition to a remarkable ability to prevent or minimise damage usually associated with such depressive changes (e.g. gut and muscle atrophy, renal failure and ischemic injuries). A coordinated shut-down of systems is essential to surviving long periods of dormancy, however, the mechanisms involved in regulating metabolic depression remain poorly understood. Aestivation, a period of dormancy that occurs in response to desiccating environments, provides an excellent model system for investigating the regulation of metabolic depression, because unlike other forms of dormancy such as hibernation, it is not confounded by changes in temperature or PO2 and thus represents a true intrinsic metabolic depression. The green striped burrowing frog, Cyclorana alboguttata, is an abundant species of burrowing frog inhabiting arid to semi-arid regions of Queensland and Northern New South Wales. During the dry season, C. alboguttata aestivates in an underground clay chamber; the aestivating period lasts on average for nine months a year, but in drought conditions may last for as long as several years. In recent years, C. alboguttata has become a well studied organism for investigating the physiological processes involved in aestivation, especially regarding muscle disuse atrophy and gut maintenance. Despite this, our understanding of this frog’s capacity to metabolically depress remains limited. The first aim of this study was to extend our current knowledge of metabolic depression during aestivation in C. alboguttata. C. alboguttata reduced whole animal metabolism by 82% within five weeks of aestivation. The effects of aestivation on mass specific in vitro tissue metabolic rate (VO2) varied among individual organs, with muscle and liver slices showing significant reductions in metabolism; kidney VO2 was elevated and there was no change in the VO2 of small intestine tissue slices. Organ size was also affected by aestivation, with significant reductions in the mass of all tissues, except the gastrocnemius. These reductions in organ size, combined with changes in mass specific VO2 of tissue slices, resulted in further energy savings to aestivating animals. Mitochondrial VO2 was significantly reduced during aestivation, by an average of 83%; in addition respiratory control ratios (RCRs), a measurement of mitochondrial coupling efficiency, significantly increased during aestivation, suggesting increased mitochondrial coupling efficiency. The second aim of this study was to investigate the potential role of the endogenous opioid system (EOS) and thyroid hormones in the regulation of metabolic depression in C. alboguttata. When incubated in the presence of opioid agonists, liver and muscle tissue slices from Cyclorana alboguttata underwent tissue- and agonist- specific metabolic depression. In most cases, the effect of opioid agonists on metabolism was more pronounced in tissue slices from aestivating animals. The delta (δ) opioid agonist DADLE was the most consistent in producing a metabolic depression, however the effect of DADLE on the metabolism of tissue slices was not reversible by the general opioid antagonist naloxone. Gene transcript levels for the δ-opioid receptor remained constant in the brain and in the muscle of aestivating C. alboguttata compared to controls. Opioid receptor XOR1 transcript levels also remained constant in the brain during aestivation compared to controls. There was a significant reduction in total thyroid hormone concentration in the plasma of C. alboguttata during aestivation, with thyroxine (T4) decreasing by 75% and an 84% reduction in triiodothyronine (T3). We also examined changes in gene expression of deiodinase 2 (D2) and deiodinase 3 (D3), the major activating and deactivating enzymes of thyroid hormones, respectively. There were no significant changes in gene expression of D2 in the brain or muscle, or of D3 in the brain; however there was a significant down-regulation of D3 transcripts in muscle tissue. In the liver, D2 was significantly down-regulated and D3 showed an increase in transcript levels that was approaching significance. During dormancy energy conservation is a key priority and as such dormant animals undergo a major metabolic depression to conserve their limited endogenous fuel supplies. At the same time, dormant animals are faced with the challenge of maintaining functional organs for immediate use upon arousal. In this study C. alboguttata appeared to selectively down- or up-regulating individual tissues, using both changes in metabolic rate and morphology. This strategy would allow maximal energy savings during aestivation without compromising organ functionality and survival at arousal. In addition, the frogs appeared to decrease rates of mitochondrial proton leak to a greater extent than ATP synthesis, consistent with an increase in mitochondrial coupling efficiency. Again, this ability to selectively down-regulate one process to a greater extent than another allows energy savings to be maximised without compromising processes essential for survival. C. alboguttata can survive in a dormant state for several years and it is hypothesised that these frogs become more energy efficient during aestivation. The regulation of metabolic depression still remains poorly understood. In this study the potential role of the EOS and thyroid hormones in regulating metabolic depression was investigated. The results of this study suggest the δ-opioid system may be responsible for the initiation of metabolic depression, while the mu (μ) and kappa (κ) opioid systems may be important during long term maintenance of aestivation. In addition, the EOS may exert its control over metabolism via both receptor and non-receptor mediated pathways. The significant down-regulation of total thyroid hormones, as well as the changes in gene expression of the thyroid deiodinases indicates thyroid hormones may also play a significant role in regulating metabolic depression. This suggests that the regulation of metabolic depression may involve several interacting systems, or perhaps a ‘systems cascade’.

Thesis (M.Sc.)--University of Alberta, 2010. / A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science in Environmental Health Sciences, School of Public Health. Title from pdf file main screen (viewed on April 27, 2010). Includes bibliographical references.

In the theoretical part of my thesis, I describe the thyroid, its importance, anatomy, creation of hormones and their regulation. There is also summarized the knowledge of external environment influences on the thyroid such as nutrition, climatic conditions or seasons and internal factors influences, mainly breed, efficiency and age. The practical part is focused on the evaluation of the thyroid activity of free-range ewes and lambs in the spring and autumn of 2013. The thesis also deals with the evaluation of possible relevance between the content of thyroid hormones in the blood serum and the physiological state of the sheep. Thanks to the correlation between TSH and thyroid hormones, the proper regulation of the thyroid of ewes and lambs was confirmed. The thyroid activity was higher in the spring than in the autumn. The hypothyroidism in the autumn was not proved because no referential values of TSH are set. In the autumn there was a lower level of glucose and cholesterol in the blood of the ewes determined which gives evidence of a lower energy income from the feed in the autumn. Also the urea level which is closely connected to the energy shortage, starvation, and high income of N substances in the feed dosage was in the autumn twice as high as in the spring. There was a positive correlation determined between the higher urea concentration and the higher thyroid activity. Owing to the change of the feed content, the TSH started to stimulate the thyroid to a higher thyroid hormones production and thus to its higher activity.