Research Papers: Gerotarget (Focus on Aging):
TSH-independent release of thyroid hormones through cold exposure in aging rats
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Abstract
Gi Cheol Park1,*, Ji Min Kim2,*, Hee-Young Park2, Ji Min Han3, Sung-Chan Shin2, Jeon Yeob Jang4, Dawoon Jung2, In Joo Kim5, Jin-Choon Lee6 and Byung-Joo Lee2
1 Department of Otorhinolaryngology – Head and Neck Surgery, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, Korea
2 Department of Otorhinolaryngology – Head and Neck Surgery, Pusan National University School of Medicine and Biomedical Research Institute, Pusan National University Hospital, Busan, Korea
3 Department of Internal Medicine, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, Korea
4 Department of Otorhinolaryngology - Head and Neck Surgery, Ajou University School of Medicine, Suwon, Korea
5 Department of Internal Medicine, Pusan National University School of Medicine and Biomedical Research Institute, Pusan National University Hospital, Busan, Korea
6 Department of Otorhinolaryngology – Head and Neck Surgery, Pusan National University School of Medicine and Biomedical Research Institute, Pusan National University Yangsan Hospital, Yangsan, Gyeongnam, Korea
* The first two authors have equally contributed to this paper
Correspondence to:
Byung-Joo Lee, email:
Keywords: aging, thyroid, cold exposure, rat, Gerotarget
Received: May 18, 2017 Accepted: July 26, 2017 Published: August 03, 2017
Abstract
Thyroid function decreases and cold exposure response becomes impaired with increasing age. We investigated the age-related changes in thyroid structure and function and cold-induced changes in the thyroid activity of aging rats. Thirty-two male Sprague–Dawley rats were randomly divided into four groups (8 rats per group): young (7 months) and old (22 months) groups exposed to room temperature and cold stress. The active follicle ratio and serum free T3, T4 and TSH, and TSH receptor (TSHR) concentrations in the thyroid tissues of the rats from each group were compared. At room temperature, old rats had significantly lower active follicle ratio and free T3 and T4 concentrations than young rats. Furthermore, old rats displayed higher TSH level than young. Exposure to cold temperature led to significantly increased active colloid ratio and free T3 and T4 concentrations among old rats, but no significant differences were found among young rats. Additionally, no significant changes in the TSH and TSHR levels were observed after cold exposure in both young and old rats. Old rats have lower thyroid function than young rats under normal temperature. Aging rats are more susceptible to cold stress than young rats, and cold-induced thyroid activation occurs independently of TSH.
We investigated the age-related changes in the thyroid structure and function and cold-induced changes in the thyroid activity of aging rats. Aging rats have structurally less active thyroid follicles and functionally lower thyroid hormone levels than young rats. Furthermore, old rats are more susceptible to cold stress than young rats, and cold-induced thyroid activation occurs independently of TSH.
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