Influence of Chronic Exposure to Cold Environment on Thyroid Gland Function in Rabbits

Abstract

Chronic exposure to cold can affect the thyroid gland. However, the effect on thyroid gland perfusion images and the ratio between thyroid hormones secretion were not addressed in any previous study. The present study investigates the effects of chronic cold exposure on thyroid gland function using radionuclide tracer and thyroid hormones secretion concentration. New Zealand white rabbits weighing approximately 1.8–2 kg were kept in a cold room (4°C) for 7 weeks. Thyroid scintigraphy was performed for cold exposed rabbits and a control rabbit group. Each rabbit was injected with 115 MBq (3.1 mCi) technetium-99m pertechnetate (99mTc pertechnetate). Studies were performed using Gamma camera equipped with a low energy, high resolution, pinhole collimator interfaced with a computer. Static images were acquired 20 min after administration of the radiotracer. Rabbits chronically exposed to cold had less body weights than control. Thyroid gland uptake is higher in rabbits chronically exposed to cold than controls using radionuclide perfusion study. The increase was proportional to the time period, so the increase after 7 weeks was greater than 5 weeks. There is also an increase in free triiodothyronine (FT3) and a decrease in free thyroxine (FT4) values. Our results indicate that thyroid gland uptake is higher in rabbits chronically exposed to cold than control and the increase was proportional to the duration. The decrease in rabbit body weights may be related to the increase in metabolism due to the increase of thyroid hormones. Chronic cold exposure also increased the conversion of T4 to T3, which is more potent in thermogenic effect.

Key words

cold - perfusion - thyroid - rabbit - thyroxine (T4) - triiodothyronine (T3) - radionuclide - ^99mTc pertechnetate

• References

• 1 Edholm OG, Lewis HE. Terrestrial animals in cold: man in polar regions. In: Dill DB, Adolph EF, Wilber CG. (ed.) Handbook of Physiology, Section 4: Adaptation to the Environment. Washington: American Physiological Society; 1964: 435-446
• 2 Budd GM, Warhaft N. Cardiovascular and metabolic responses to noradrenaline in man, before and after acclimatization to cold in Antarctica. J Physiol 1966; 186: 233-242
• 3 Budd GM, Warhaft N. Body temperature, shivering, blood pressure and heart rate during a standard cold stress in Australia and Antarctica. J Physiol 1966; 186: 216-232
• 4 Budd GM. Skin temperature, thermal comfort, sweating, Clothing and activity of men sledging in Antarctica. J Physiol 1966; 186: 201-215
• 5 Andersen S, Kleinschmidt K, Hvingel B, Laurberg P. Thyroid hyperactivity with high thyroglobulin in serum despite sufficient iodine intake in chronic cold adaptation in an Arctic Inuit hunter population. Eur J Endocrinol 2012; 166: 433-440
• 6 Ingbar SH, Bass DE. The effect of prolonged exposure to cold on production and degradation of thyroid hormone in man. J Endocrinol 1967; 37 II–III
• 7 Rudas P, Pethes G. Acute changes of the conversion of thyroxine to triiodothyronine in hypophysectomized and thyroidectomized chickens exposed to mild cold (10 degrees). Gen Comp Endocrinol 1986; 63: 408-413
• 8 Raud HR, Odell WD. The radioimmunoassay of human thyrotropin. Br J Hosp Med 1969; 2: 1366-1376
• 9 Eastman CJ, Ekins RP, Leith IM, Williams ES. Thyroid hormone responses to prolonged cold exposure in man. J Physiol 1974; 241: 175-181
• 10 Eastman A. Augmentation of the peripheral metabolism of L-triiodothyronine and L-thyroxine after acclimation to cold. J Clinc Invest 1974; 53: 980-987
• 11 Hefco E, Krulich L, Illner P, Larsen PR. Effect of acute exposure to cold on the activity of the hypothalamic-pituitary-thyroid system. Endocrinology 1975; 97: 1185-1195
• 12 Levine M, Duffy L, Moore DC, Matej LA. Acclimation of a non-indigenous sub-Arctic population: seasonal variation in thyroid function in interior Alaska. Comp Biochem Physiol A Physiol 1995; 111: 209-214
• 13 Fisher DA, Odell WD. Acute release of thyrotropin in the newborn. J Clin Invest 1969; 48: 1670
• 14 Fisher DA, Oddie TH. Neonatal thyroidal hyperactivity. Response to cooling. Am J Dis Child 1964; 107: 574-581
• 15 Wilber JF, Baum D. Elevation of plasma TSH during surgical hypothermia. J Clin Endocrinol Metab 1970; 31: 372-375
• 16 Van Do N, Mino L, Merriam G, LeMAr H, Case HS, Palinkas LA, Reedy K, Reed HL. Elevation in serum thyroglobulin during prolonged Antarctic residence: Effect of thyroxine supplement in the polar 3,5,3′-triidothyronine syndrome. J Clin Endocrinol Metab 2004; 89: 1529-1533
• 17 Laurberg P, Andersen S, Karmisholt J. Cold adaptation and thyroid hormone metabolism. Horm Metab Res 2005; 37: 545-549
• 18 Dunn JT, Dunn AD. Update on intrathyroidal iodine metabolism. Thyroid 2001; 11: 407-414
• 19 Dentice M, Salvatore D. Deiodinases. the balance of thyroid hormone: local impact of thyroid hormone inactivation. J Endocrinol 2011; 209: 273-282
• 20 Williams GR, Bassett JH. Deiodinases: the balance of thyroid hormone: local control of thyroid hormone action: role of type 2 deiodinase. J Endocrinol 2011; 209: 261-272
• 21 Balsam A, Sexton FC. Increased metabolism of iodothyronines in the rat after short-term cold adaptation. Endocrinology 1975; 97: 385
• 22 Bernal J, Escobar del Rey F. Effect of the exposure to cold on the extrathyroidal conversion of L-thyroxine to triiodo-L-thyronine, and on intramitochondrial glycerophosphate dehydrogenase activity in thyroidectomized rats on L-thyroxine. Acta Endocrinol 1975; 78: 481
• 23 Tsukahara F, Uchida Y, Ohba K, Nomoto T, Muraki T. Defective stimulation of thyroxine 5′-deiodinase activity by cold exposure and norepinephrine in brown adipose tissue of monosodium glutamate-obese mice. Horm Metab Res 1997; 29: 496-500
• 24 Balsam A, Leppo LE. Augmentation of the peripheral metabolism of L-triiodothyronine and Lthyroxine after acclimation to cold. Multifocal stimulation of the binding of iodothyronines by tissues. J Clin Invest 1974; 53: 980
• 25 Galton VA, Nisula BC. Thyroxine metabolism and thyroid function in the cold-adapted rat. Endocrinology 1969; 85: 79-86
• 26 Silvestri E, Schiavo L, Lombardi A, Goglia F. Thyroid hormones as molecular determinants of thermogenesis. Acta Physiol Scand 2005; 184: 265-283
• 27 Ishii H, Inada M, Tanaka K, Mashio Y, Naito K, Nishikawa M, Imura H. Triiodothyronine generation from thyroxine in human thyroid: enhanced conversion in Graves’ thyroid tissue. J Clin Endocrinol Metab 1981; 52: 1211-1217
• 28 Salvatore D, Tu H, Harney JW, Larsen PR. Type 2 iodothyronine deiodinase is highly expressed in human thyroid. J Clin Invest 1996; 98: 962-968
• 29 Bartalena L, Bogazzi F, Brogioni S, Burelli A, Scarcello G, Martino E. Measurement of serum free thyroid hormone concentrations. an essential tool for the diagnosis of thyroid dysfunction. Horm Res 1996; 45: 142-147