The effects of ovarian hormones and seasons on Anolis carolinensis. I. The thyroid

Evans, Llewellyn Thomas; Hegre, Erling S.

doi:10.1002/ar.1090720102

Cited by 20 publications

(5 citation statements)

References 8 publications

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“…Poikilotherms on the other hand, generally show a decrease in both thyroid activity and metabolism in the cold (5,12). There are, however, reports of reptiles that maintain higher levels of thyroid activity during cool periods (11,29,30,32).…”

mentioning

confidence: 99%

Cold-induced changes in thyroid function in a poikilothermic mammal, the naked mole-rat

Buffenstein

Woodley²,

Thomadakis³

et al. 2001

American Journal of Physiology-Regulatory, Integrative and Comp

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Cold acclimation induces very divergent responses in thyroid function in reptiles and mammals reflective of their different thermoregulatory modes. Naked mole-rats, unlike other small mammals, are unable to effectively employ endothermy and are operatively poikilotherms. We therefore investigated changes in their thyroid status with chronic cold exposure. Under simulated burrow conditions, free thyroxine (T(4); 0.39 +/- 0.09 ng/dl) and thyroid stimulating hormone (TSH; 1.12 +/- 0.56 microIU/ml) levels fell within the reptilian range, one order of magnitude lower than mammalian levels. However, cold induced typical mammalian responses: free T(4) levels (0.55 +/- 0.09 ng/dl) and thyroid follicular cell height were significantly greater. Although TSH levels (1.28 +/- 0.83 microIU/ml) were not significantly elevated, thyrotrophs exhibited ultrastructural signs of increased secretory activity. Low thyroid hormone concentrations may contribute substantially to the unusual thermoregulatory mode exhibited by naked mole-rats.

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mentioning

confidence: 99%

Cold-induced changes in thyroid function in a poikilothermic mammal, the naked mole-rat

Buffenstein

Woodley²,

Thomadakis³

et al. 2001

American Journal of Physiology-Regulatory, Integrative and Comp

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“…This is surprising in view of numerous reports that ovula¬ tion and egg-laying are associated with increased thyroid activity (Evans & Hegre, 1938;Miller, 1955;Saint Girons, 1963;Wilhoft, 1963Wilhoft, , 1964; see also review by Lynn, 1970). However, measurement of epithelial cell height, which was the sole basis for assessing thyroid activity in these studies, may not be a very reliable para¬ meter of thyroid function.…”

Section: Female Lizardsmentioning

confidence: 95%

Thyroid Activity and Oxidative Metabolism in a Species of Gecko (Hemidactylus Flaviviridis Rüppell) in Relation to Sex Hormones

Chandola¹,

Ds²,

Jp³

1974

Journal of Endocrinology

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Orchidectomy in Hemidactylus flaviviridis led to significant reduction of thyroidal 131I uptake, thyroidal content of thyroxine, plasma protein-bound iodine and oxygen consumption of isolated liver and skeletal muscle (at 30 \ s=deg\ C). Administration of testosterone to orchidectomized lizards restored these parameters to normal levels. Dependence of thyroid function and oxidative metabolism on male hormone may be a general feature in reptiles. This hormone may, therefore, be of greater physiological importance in these animals than in other vertebrates. Since reptiles occupy a crucial phylogenetic position in the animal kingdom these findings are important from the point of view of evolution of the functional aspects of hormones in vertebrates.The results also show that thyroid function is inhibited by oestrogen(s) in this lizard. This may be an adaptive compensatory measure to control (through effects of the thyroid on metabolic activities) the extra expenditure of energy usually associated with such energy-consuming functions as ovulation and egg-laying.

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“…The specific relationship between the HPT axis and reproduction was reviewed by T A B L E 1 Interactions of thyroid hormones and reproductive events in amphibians. Early studies (e.g., Evans & Hegre, 1938;Miller, 1955Miller, , 1963 supported a positive role for thyroid hormones in the reproduction of reptiles. However, these studies based the assessment of thyroid activity entirely on the histological appearance of the thyroid glands, a characteristic that is dependent on TSH stimulation and not on rates of hormone secretion by the thyroid follicle cells (see Norris & Carr, 2021).…”

Section: Thyroid Hormones and Reproduction In Reptilesmentioning

confidence: 99%

Thyroid and reproduction in amphibians and reptiles

Norris

2023

J Exp Zool Pt A

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The relationship between the thyroid gland and reproduction in amphibians and reptiles has been studied for more than 100 years. Most studies suggest a positive involvement of thyroid hormones with some aspects of reproduction, but some studies support a negative role for thyroid hormones at certain life stages. Comprehensive studies of gene activation/suppression by thyroid hormones and their absence at various levels of the hypothalamo–pituitary–gonadal axis coupled with observations of adrenocorticoid activity, reproductive performance, and metabolic involvement are needed to understand this complex relationship.

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The effects of ovarian hormones and seasons on Anolis carolinensis. I. The thyroid

Abstract: Ilur vnrd Bid o g icnl Labu rat o r ics, Ca?nbrid.qc, Mmsuch u b ct is, and Monlanu Stole liniversity, Xisaouln OXE PLATE (TEN FIGURES)

Cited by 20 publications

References 8 publications

Cold-induced changes in thyroid function in a poikilothermic mammal, the naked mole-rat

Cold-induced changes in thyroid function in a poikilothermic mammal, the naked mole-rat

Thyroid Activity and Oxidative Metabolism in a Species of Gecko (Hemidactylus Flaviviridis Rüppell) in Relation to Sex Hormones

Thyroid and reproduction in amphibians and reptiles

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