Thyroid hormones correlate with field metabolic rate in ponies,<i>Equus ferus caballus</i>

Brinkmann, Lea; Gerken, M.; Hambly, Catherine; Speakman, John R.; Riek, Alexander

doi:10.1242/jeb.138784

Cited by 21 publications

(14 citation statements)

References 61 publications

(84 reference statements)

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“…We believe that determinations of total T4 levels are as important as those of fT4 levels in assessing thyroid gland function. This is supported by previous reports showing that fT4 concentrations in plasma are highly correlated with total T4 concentrations [ 3 , 8 , 38 ]. Interestingly, total T4 levels in yearlings obtained in our RIA, 225.98 ± 20.89 n g/m l , were dramatically different from the reference values of 35 n g/m l [ 27 ] and 68.68 ± 2.0 n g/m l in horses at 6 months to 1 year of age, or 34.61 ± 0.92 n g/m l in horses 1–3 years of age [ 17 ].…”

Section: Discussionsupporting

confidence: 90%

“…Radioimmunoassay (RIA) is considered the gold standard method to determine thyroid hormone levels, because RIA exhibits high sensitivity and specificity and low detection limits [ 2 , 14 , 15 , 20 , 21 , 29 , 30 ]. Furthermore, equilibrium dialysis [ 2 ], ultrafiltration [ 31 ], enzyme immunoassay [ 3 , 23 , 33 , 34 ], chemiluminescence immunoassay [ 10 , 28 ], chemiluminescent enzyme immunoassay [ 11 ] and electrochemiluminescence immunoassay [ 10 , 39 ] are available to evaluate thyroid function in many species. Nonetheless, reference values of thyroid hormone concentrations vary substantially by measurement techniques used and laboratories performing the assays.…”

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confidence: 99%

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Sensitive radioimmunoassay of total thyroxine (T4) in horses using a simple extraction method

Tangyuenyong

Nambo

Nagaoka

et al. 2017

The Journal of Veterinary Medical Science

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Most thyroid hormone determinations in animals are based on immunoassays adapted from those used to test human samples, which may not reflect the actual values of thyroid hormone in horses because of the presence of binding proteins. The aims of the present study were i) to establish a novel radioimmunoassay (RIA) using a more simple and convenient method to separate binding proteins for the measurement of total thyroxine (T4) in horses and ii) to validate the assay by comparing total T4 concentrations in yearling horses raised in different climates. Blood samples were collected from trained yearlings in Hokkaido (temperate climate) and Miyazaki (subtropical climate) in Japan and from adult horses in estrus and diestrus. T4 was extracted from both serum and plasma using modified acid ethanol cryo-precipitation and sodium acetate ethanol methods. Circulating total T4 concentrations were determined by RIA. T4 concentration by sodium acetate ethanol was appropriately detectable rather than sodium salicylate method and was the same as for acid ethanol method. Furthermore, this sodium acetate ethanol method required fewer extraction steps than the other methods. Circulating T4 concentrations in yearlings were 225.98 ± 20.89 ng/ml, which was higher than the previous reference values. With respect to climate, T4 levels in Hokkaido yearlings tended to be higher than those in Miyazaki yearlings throughout the study period. These results indicated that this RIA protocol using a modified sodium acetate ethanol separation technique might be an appropriate tool for specific measurement of total T4 in horses.

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Section: Discussionsupporting

confidence: 90%

mentioning

confidence: 99%

Sensitive radioimmunoassay of total thyroxine (T4) in horses using a simple extraction method

Tangyuenyong

Nambo

Nagaoka

et al. 2017

The Journal of Veterinary Medical Science

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“…Accordingly, a positive relationship between thyroid hormone levels and metabolic rate has been found in captive reptiles (Joos and John-Alder, 1990), birds (Vézina et al, 2009) and mammals (Banta and Holcombe, 2002;Brinkmann et al, 2016;Li et al, 2010), including humans (reviewed in Hulbert, 2000;Kim, 2008). In contrast, other studies report no relationship between metabolic rate and thyroid hormones in captive mammals (Nilssen et al, 1984;Ostrowski et al, 2006), including humans (Bernstein et al, 1983;Johnstone et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

“…Thyroid hormones are believed to play a key role in the regulation of seasonal and acute changes in metabolism, and the regulating function of thyroid hormones should be especially important during periods of reduced food availability, when animals should lower energy expenditure (Brinkmann et al, 2016;Flier et al, 2000;Fuglei and Øritsland, 1999;Zhan et al, 2009). Accordingly, laboratory studies on humans (Carlson et al, 1977;Gardner et al, 1979), other mammals and birds found that thyroid hormone levels decrease when individuals are food deprived (Brinkmann et al, 2016;Diano et al, 1998;Mustonen et al, 2008;Nieminen et al, 2001) and increase during periods of high food intake (Fuglei et al, 2000;Stokkan et al, 1985). However, few field studies tested whether free-living animals show seasonal changes in thyroid hormone levels as an adaptation to changes in food availability.…”

Section: Introductionmentioning

confidence: 99%

Both thyroid hormone levels and resting metabolic rate decrease in African striped mice when food availability decreases

Rimbach

Pillay

Schradin

2016

Journal of Experimental Biology

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In response to variation in food availability and ambient temperature (T a ), many animals show seasonal adaptations in their physiology. Laboratory studies showed that thyroid hormones are involved in the regulation of metabolism, and their regulatory function is especially important when the energy balance of an individual is compromised. However, little is known about the relationship between thyroid hormones and metabolism in free-living animals and animals inhabiting seasonal environments. Here, we studied seasonal changes in triiodothyronine (T 3 ) levels, resting metabolic rate (RMR) and two physiological markers of energy balance (blood glucose and ketone bodies) in 61 free-living African striped mice (Rhabdomys pumilio) that live in an semi-arid environment with food shortage during the dry season. We predicted a positive relationship between T 3 levels and RMR. Further, we predicted higher T 3 levels, blood glucose levels and RMR, but lower ketone body concentrations, during the moist season when food availability is high compared with summer when food availability is low. RMR and T 3 levels were negatively related in the moist season but not in the dry season. Both RMR and T 3 levels were higher in the moist than in the dry season, and T 3 levels increased with increasing food availability. In the dry season, blood glucose levels were lower but ketone body concentrations were higher, indicating a change in substrate use. Seasonal adjustments in RMR and T 3 levels permit a reduction of energy expenditure when food is scarce, and reflect an adaptive response to reduced food availability in the dry season.

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“…For chronically cold weather, serum thyroid hormone and metabolic rate did not change significantly from autumn to spring [ 28 ]. In the case of long-term exposure to low temperatures in other species, thyroid hormone levels increased and resulted in stimulation of metabolism and heat production in sows [ 1 ], sheep [ 34 ], and cattle [ 11 ]; horses, on the other hand, employed a state of hypometabolism to keep their bodies warm [ 5 , 6 , 26 ].…”

Section: Discussionmentioning

confidence: 99%

Comparison of physical body growth and metabolic and reproductive endocrine functions between north and south climates of Japan in trained Thoroughbred yearling horses

Tangyuenyong

Sato

Nambo

et al. 2017

JES

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This study aimed to compare body growth, metabolic, and reproductive hormonal changes in trained Thoroughbred yearling horses under different climate conditions with and without light supplementation (LS). Thoroughbred yearlings raised at research centers of the Japan Racing Association in Hokkaido (north) or Miyazaki (south) were divided into control and LS groups. In the LS groups, 44 colts and 47 fillies from Hokkaido and 11 colts and 11 fillies from Miyazaki were exposed to LS with an extended photoperiod of 14.5 hr of daylight and 9.5 hr of darkness. One week before and once a month after LS, circulating total thyroxine (T4), insulin-like growth factor-I (IGF-1), prolactin (PRL), cortisol, and progesterone (P4) concentrations were measured by radioimmunoassay and fluoroimmunoassay, respectively. Growth parameters, including body weight, height, girth, and cannon bone circumferences, were measured monthly. Hair coat (HC) condition was scored. Under natural conditions, the T4 concentrations of Hokkaido yearlings tended to be higher, whereas the IGF-1 (colt) and PRL levels were significantly lower than those of yearlings in Miyazaki. Growth parameters and HC scores were lower in Hokkaido yearlings. With LS, the PRL and P4 concentrations in Hokkaido and Miyazaki were higher, and the first ovarian activity tended to be earlier than in the controls. Only LS Hokkaido yearlings showed significantly higher HC scores than the controls. Comparing the different climates among the LS yearlings, the levels of PRL and P4 and the HC scores in Hokkaido yearlings increased and reached levels similar to those in Miyazaki yearlings. The body weight and girth increment percentages of Hokkaido yearlings in January dramatically decreased and then eventually increased to levels similar to those of Miyazaki yearlings. This suggested that yearlings in naturally colder Hokkaido exhibit higher basal metabolism to maintain homeostasis. However, providing LS may help to improve growth and early development of reproductive function in Hokkaido yearlings to levels equal to those of Miyazaki horses.

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Thyroid hormones correlate with field metabolic rate in ponies,Equus ferus caballus

Cited by 21 publications

References 61 publications

Sensitive radioimmunoassay of total thyroxine (T4) in horses using a simple extraction method

Sensitive radioimmunoassay of total thyroxine (T4) in horses using a simple extraction method

Both thyroid hormone levels and resting metabolic rate decrease in African striped mice when food availability decreases

Comparison of physical body growth and metabolic and reproductive endocrine functions between north and south climates of Japan in trained Thoroughbred yearling horses

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