A Multicompartmental Model for Iodide, Thyroxine, and Triiodothyronine Metabolism in Normal and Spontaneously Hyperthyroid Cats.

Hays, Marguerite T.; Broome, Michael R.; Turrel, Jane M.

doi:10.1097/00003072-198709001-00042

Cited by 4 publications

(7 citation statements)

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Section: Discussionunclassified

“…A escolha deste intervalo de tempo deve-se ao pico de concentração da tiroxina em gatos após a administração oral ser de 3-4 horas (HAYS et al, 1988). A meia-vida da tiroxina por via oral em gatos é de aproximadamente 10,7 horas (HAYS et al, 1988). Entretanto não há necessidade da administração duas vezes ao dia, visto que a meia-vida não indica necessariamente a extensão ou duração da ação biológica do hormônio (PETERSON e FERGUSON, 1992).…”

Section: Discussionunclassified

“…Visto que os gatos não apresentavam enfermidades não tireoidianas concomitantes e, também não foi administrada qualquer droga que pudesse interferir nos valores de TT4. Outra hipótese é a desiodinação acelerada de TT4 formando uma grande quantidade de TT3, porém está hipótese é pouco provável pois o aumento do TT3 encontrado foi insignificante e, além disso, o T3 é um hormônio essencialmente intracelular (HAYS et al, 1988; Manifestações clínicas em gatos com hipertireoidismo experimental KAPTEIN et al, 1994). Alguns gatos hipertireóideos podem apresentar variação nas concentrações hormonais, isto é, os hormônios aumentam e diminuem durante o dia (MOONEY et al, 1996b;PETERSON, , 2004.…”

Section: Discussionunclassified

“…Porém, optamos em fazer a colheita quatro horas após a administração oral da levotiroxina sódica. A escolha deste intervalo de tempo deve-se ao pico de concentração da tiroxina em gatos após a administração oral ser de 3-4 horas e inferior a meia-vida que é de 10,7 horas (HAYS et al, 1988).…”

Section: Discussionunclassified

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Manifestações Clínicas Em Gatos Com Hipertireoidismo Experimental

Cardoso¹,

Costa²,

Muniz³

et al. 2005

AVS

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RESUMO -A relação do hipertireoidismo experimental com parâmetros clínicos foi avaliada em gatos machos e fêmeas, intactos e mantidos em estado hipertireóideo por um período de 42 dias. Os parâmetros estudados foram consumo diário de água e ração, débito urinário, o volume fecal, peso corporal, temperatura corporal, coloração de membranas mucosas, palpação de linfonodos superficiais, palpação da glândula tireóide, pulso femoral, auscultação cardíaca e respiratória, freqüência cardíaca e respiratória e palpação abdominal. Correlacionou-se as variáveis com os níveis de T3 total, T4 livre e total. O excesso dos hormônios tireoidianos acompanhou aumento da freqüência cardíaca, polifagia, polidipsia, perda de peso e aumento do volume fecal nos gatos estudados.Palavras-chave: gatos, tireóide, manifestações clínicas, hipertireoidismo, T3, T4. SUMMARY -The interrelation between experimental hyperthyroidism andclinical changes was studied in adult intact cats kept under hyperthyroidic state for 42 days. Clinical aspects evaluated were dairy food and water intake, urine output and fecal volume, body weight, temperature, mucous membranes colour, palpable lymphnodes, thyroid gland palpation, abdominal palpation, and cardiac and respiratory frequencies. These characteristics were correlated with free and total T4 and total T3 serum concentrations. Excessive circulant thyroid hormone levels resulted in increased cardiac frequency, polyuria, polidipsia, weight loss and increased fecal volume in the studied cats.

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Section: Discussionunclassified

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Manifestações Clínicas Em Gatos Com Hipertireoidismo Experimental

Cardoso¹,

Costa²,

Muniz³

et al. 2005

AVS

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“…However, such a model is difficult to define provided the complexity of the different processes involved and the lack of specific information on their lunetic properties. Previous models of thyroid metabolism have focused on the distribution of hormones in different body compartments through the analysis of injected radioactive tracers (see for instance Hays et al, 1988;Jacobs et al, 1997). Hatakeyama and Yagi (1985) proposed a model based on linear kinetics.…”

Section: Introductionmentioning

confidence: 99%

The Power‐Law Formalism as a Tool for Modeling Hormonal Systems

Sorribas

González

1999

Computational and Mathematical Methods in Medicine

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Modeling a hormone system requires a number of simplifying assumptions. Often, the final conceptual model incorporates a number of aggregated processes that have no correspondence with a single enzyme-catalyzed reaction. In such cases, it is discussible using models based on classical biochemical kinetics rate laws that are valid only under specific conditions. The power-law formalism provides an alternative framework for building up a mathematical model in such cases. The resulting model is a set of ordinary differential equations with a special structure that allows efficient symbolic and numerical analysis of the system's properties. In these equations, the underlying rate-laws of each of the component processes are represented by a power-law that is an exact representation of the actual rate-law at the operating point. The particular form of these equations allows representation of a wide range of kinetic features without changing the basic power-law form. Moreover, its parameters have an immediate interpretation as apparent kineticorders and rate-constants. This is especially helpful for incorporating both quantitative and qualitative information in the process of model definition. This is particularly useful when detailed kinetic information concerning system's components is not available. In this paper we show the utility of the power-law approach in this context by deriving an illustrative model of a complex physiological system: the hypothalamus-anterior pituitarythyroid network. First, we derive a conceptual model that incorporates the key features of this system. Then, we derive an S-system model, one of the preferred variants within the power-law formalism, and we show its utility in exploring the system properties. The model qualitatively reproduces the response of normal, hyperthyroid, and hypothyroid patients to a clinical test involving a thyrotropin releasing hormone injection. Finally, we illustrate the utility of this modeling strategy for studying the system's response to different dynamic patterns of regulatory signals, and for exploring how altered dynamic patterns of stimulatory signals can cause pathological states.

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Establishing levels of retained radioactivity in cats receiving radioactive iodine treatment

Alonzi¹,

Peak²,

Gower³

et al. 2021

Veterinary Record

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Background: Radioactive iodine (RAI) is considered the gold standard treatment for feline hyperthyroidism. Currently exposure limits to radiation are regulated by national legislation, therefore the length of the isolation period in hospital for cats receiving radioactive treatment varies according to the place where the radioactive facility is located. The aim of this study was to establish when retained radioactivity decreases in cats receiving subcutaneous I‐131 to a level that would allow discharge of cats from the hospital while being compliant with current United Kingdom legislation. Methods: Clinical records of cats treated with subcutaneous I‐131 were retrospectively reviewed. Radioactive emission rates were measured using an external probe. Retained radioactivity below 11 MBq at the point of discharge was required by the initial risk assessment to ensure that a 0.3 mSv dose constraint was maintained for owners following standard cat‐owner contact restrictions. Average retained activity for each treatment regimen at the time of discharge was calculated. The biological half‐life for iodine retention was also calculated. Results: Overall, an end activity below 11 MBq was reached at day 11 in 49% of cats, and at day 13 in 91% of cats. These cats were allowed to be discharged according to UK legislation, as long as contact restrictions were applied at home for 2 weeks. Conclusion: Based on our study, an isolation period of 13 days before allowing discharge of cats treated with subcutaneous RAI (I‐131) is compliant with current UK legislation.

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A Multicompartmental Model for Iodide, Thyroxine, and Triiodothyronine Metabolism in Normal and Spontaneously Hyperthyroid Cats.

Cited by 4 publications

References 0 publications

Manifestações Clínicas Em Gatos Com Hipertireoidismo Experimental

Manifestações Clínicas Em Gatos Com Hipertireoidismo Experimental

The Power‐Law Formalism as a Tool for Modeling Hormonal Systems

Establishing levels of retained radioactivity in cats receiving radioactive iodine treatment

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