Effects of ambient temperature and thyroid hormones on food intake by pigs

Macari, Marcos; Zuim, S.M Fontes; Secato, Euclides Roberto; Guerreiro, JoséR.

doi:10.1016/0031-9384(86)90476-2

Cited by 16 publications

(14 citation statements)

References 19 publications

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“…They stimulate oxidative phosphorylation and ATP exportation [12,14] and mitochondria biogenesis [9]. Their decreased concentrations at high temperature [21,32] are consistent with the reduction in heat production in observed in such conditions [23,27]. However, in our study, only plasma T 4 concentrations were significantly lowered at high temperature.…”

Section: Discussionsupporting

confidence: 87%

Effects of high temperature on body temperature and hormonal adjustments in piglets

2002

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-Effects of a high (33°C) or thermoneutral (23 °C) temperature on body temperature and endocrine parameters were studied in weaned piglets. Rectal and skin temperatures were measured in four ad libitum fed animals per temperature during three weeks. After this acclimation period, 11 blood samples were withdrawn on a 24-h period. Over the acclimation period, rectal and skin temperatures were 0.6 and 2.9°C higher, respectively, at 33°C than at 23°C (P < 0.01), this change occurring from the 1st day at 23 or 33°C. A tendency of serum leptin concentrations to be lower after meals at 33°C than at 23°C was also displayed (P = 0.09). Plasmatic concentrations in Insulin-like growth factor I and thyroxine were decreased at 33°C relative to 23°C (P < 0.01 and P < 0.06, respectively), and triiodothyronine concentrations tended to be lower at 33°C than at 23°C (P = 0.1), which could account for the lower heat production and growth observed in pigs exposed to high temperatures.piglet / heat exposure / body temperature / thyroid hormones / IGF-I Résumé -Effets d'une température ambiante élevée sur la température corporelle et les ajustements hormonaux chez le porcelet sevré. Les effets d'une température ambiante élevée (33°C) ou thermoneutre (23°C) sur la température corporelle et le statut hormonal sont étudiés chez le porcelet sevré. Les températures rectale et cutanée sont mesurées sur 4 animaux par tempé-rature, nourris à volonté et acclimatés à la température expérimentale pendant trois semaines. Après cette période, les paramètres sanguins sont mesurés sur 11 échantillons prélevés sur un nycthémère. Au cours de la période d'acclimatation, les températures rectale et cutanée sont rapidement supérieures à 33°C qu'à 23°C, respectivement de 0,6 et 2,9°C (P < 0,01). Les concentrations sériques en leptine tendent à être inférieures à 33°C à l'état nourri (P = 0,09). Les taux d'Insulin-like growth factor I et thyroxine plasmatiques sont plus faibles à 33 qu'à 23°C (respectivement P < 0,01 et P < 0,06), et les concentrations en triiodothyronine tendent à être inférieures à 33°C (P = 0,1), en accord avec la production de chaleur et la croissance plus faible de ces animaux au chaud.porcelet / chaleur / température corporelle / hormones thyroïdiennes / IGF-I Reprod. Nutr. Dev. 42 (2002) 45-53 45

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Section: Discussionsupporting

confidence: 87%

Effects of high temperature on body temperature and hormonal adjustments in piglets

2002

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“…However, different underlying mechanisms were probably responsible for the increases in body weights in the hypothyroid group and in the hyperthyroid animals on extra food intake. Because of the effects of THs on basal metabolic rate (BMR), voluntary food intake is generally decreased in hypothyroidism and increased in the hyperthyroid state (20). The reduction in BMR in hypothyroidism increases the ratio of energy intake to energy expenditure relative to euthyroid animals consuming the same amount of food.…”

Section: Discussionmentioning

confidence: 99%

“…The precise mechanisms by which energy intake modifies circulating IGF-I concentrations are unclear, although they may involve changes in circulating thyroid and pancreatic hormone levels (19). Direct assessment of the effects of thyroid status on IGF-I is difficult, because THs themselves influence energy expenditure and voluntary food intake (20). Thus, THs have the capacity to affect IGF-I levels indirectly by their effect on energy balance.…”

Section: Introductionmentioning

confidence: 99%

Effects of thyroid status on insulin-like growth factor-I, growth hormone and insulin are modified by food intake

Morovat

Dauncey

1998

European Journal of Endocrinology

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Understanding the interactions between metabolic signals that regulate insulin-like growth factor-I (IGF-I) is crucial to a recognition of mechanisms that control mammalian growth. Thyroid hormones (THs) are essential for normal growth and development, and it has been suggested previously that they can modify circulating IGF-I concentrations. However, the fact that THs influence food intake, which can itself affect plasma IGF-I levels, has been ignored in previous studies. We have therefore investigated the effects of thyroid status on plasma IGF-I under conditions of controlled food intake in young growing pigs. Circulating IGF-I, growth hormone (GH) and insulin levels, were studied in hypo-and hyperthyroid animals on the same level of food intake as euthyroid controls. In addition, a separate group of hyperthyroid animals was given double the amount of food, in order to assess the influence of increased food intake, as would occur naturally in the hyperthyroid state. Hypothyroid animals and hyperthyroids with extra food had the greatest increase in body weight over the 3 weeks of treatment. These two groups had significantly higher circulating IGF-I and insulin concentrations than either the euthyroid or hyperthyroid animals on the same food intake. Integration of GH concentrations from samples taken every 20 min over a 9 h period showed that, by contrast with IGF-I and insulin levels, GH levels were significantly lower in hypothyroids and hyperthyroids on extra food compared with the euthyroids and the hyperthyroids on the same food intake. We conclude that the effects of thyroid status on IGF-I are mediated in part by the effects that THs have on energy balance, and that nutritional signals are capable of modifying the influence of thyroid status per se on circulating IGF-I concentrations. European Journal of Endocrinology 138 95-103

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“…In hypothyroidism, body mass index is often increased, whereas in hyperthyroidism there is a tendency to weight loss (Ingbar 1985, Romiti et al 1998, Wesche et al 1998. A correlation has been established between circulating concentrations of thyroid hormones and energy expenditure (Macari et al 1986, Iossa et al 1996. Energy homeostasis, body weight, and food uptake are also regulated by leptin, the protein product of the ob gene (Zhang et al 1994, Rohner-Jeanrenaud & Jeanrenaud 1996, Roth et al 1998.…”

Section: Introductionmentioning

confidence: 99%

Immunoreactive leptin and leptin mRNA expression are increased in rat hypo- but not hyperthyroidism

Leonhardt

Gerdes²,

Ritzel³

et al. 1999

Journal of Endocrinology

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In this study, plasma leptin concentrations were measured in rats artificially rendered hyper-or hypothyroid by administration of thyroxine or TRH, by administration of methimazole, or by thyroidectomy. Compared with those in untreated controls, leptin immunoreactivity was not affected in the hyperthyroid state, but was significantly increased in hypothyroid animals. Methimazole administration for longer time periods caused a stepwise increase in plasma leptin immunoreactivity. Greatest leptin concentrations were seen after 28 days of methimazole. Seven days after withdrawal of the methimazole, leptin concentrations no longer differed from those observed in control animals. In hypothyroid animals, expression of leptin mRNA was increased in both retroperitoneal and epididymal adipose tissue, whereas no difference was seen for subcutaneous or mesenteric fat. Incubation of rat leptin with plasma of eu-or hypothyroid rats and subsequent HPLC analysis of leptin plasma peaks gave no indication of an altered hormone stability. We conclude that, in hypothyroid rats, leptin concentrations may be increased as a result of stimulated leptin synthesis in retroperitoneal and epididymal adipose tissue.

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Effects of ambient temperature and thyroid hormones on food intake by pigs

Cited by 16 publications

References 19 publications

Effects of high temperature on body temperature and hormonal adjustments in piglets

Effects of high temperature on body temperature and hormonal adjustments in piglets

Effects of thyroid status on insulin-like growth factor-I, growth hormone and insulin are modified by food intake

Immunoreactive leptin and leptin mRNA expression are increased in rat hypo- but not hyperthyroidism

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