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Thyroid function in male Zucker rats exposed to cold
E M Whitaker1, A C Robinson, K M Rayfield
1Department of Physiology, University of Leeds.
Quarterly Journal of Experimental Physiology (Cambridge, England)
|November 1, 1988
Summary
Cold exposure increases thyroid stimulating hormone (TSH) and brown adipose tissue (BAT) in both obese and non-obese Zucker rats. Obese rats showed a greater response, indicating no thyroid defect in cold adaptation.
Area of Science:
- Physiology
- Endocrinology
- Metabolism
Background:
- Obesity is linked to metabolic dysregulation.
- Brown adipose tissue (BAT) plays a role in non-shivering thermogenesis and energy expenditure.
- Thyroid hormones are critical regulators of metabolism and thermogenesis.
Purpose of the Study:
- To investigate the thyroid function and BAT response to cold in obese versus non-obese Zucker rats.
- To determine if congenital obesity affects the ability to adapt to cold environments.
Main Methods:
- Non-obese and obese Zucker rats were subjected to cold stress (6°C) for 20 days.
- Measurements included thyroid stimulating hormone (TSH), circulating thyroid hormones (free thyroxine, 3,5,3'-triiodothyronine), and tissue weights (thyroid gland, BAT).
Main Results:
- Both rat groups exhibited increased TSH and 3,5,3'-triiodothyronine concentrations in response to cold.
- Brown adipose tissue weight significantly increased in both phenotypes, with a more pronounced effect in obese rats.
- Obese rats displayed lower free thyroxine levels compared to non-obese rats.
Conclusions:
- Congenitally obese Zucker rats demonstrate a functional thyroid axis and BAT response when exposed to cold.
- Obese rats exhibit an enhanced thermogenic response to cold, suggesting preserved or augmented adaptive mechanisms.
- These findings challenge the notion of a thyroid defect in obese Zucker rats' response to cold stress.
