An evidence for the transcriptional regulation of iodothyronine deiodinase 2 by progesterone in ovarectomized rats
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ORIGINAL PAPER
An evidence for the transcriptional regulation of iodothyronine deiodinase 2 by progesterone in ovarectomized rats Hossam A. Awad & Zienab A. Alrefaie
Received: 25 July 2013 / Accepted: 5 December 2013 # University of Navarra 2013
Abstract Recent literature lacks studies on the effects of progesterone withdrawal on peripheral conversion of thyroxin (T4) into triiodothyronine (T3) by iodothyronine deiodinase 2 (D2) in different body tissues. The present study aimed to assess the possible relation of progesterone to T4, T3, and D2 in ovarectomized rats. Thirty female Wistar rats were included into a sham-operated control group and an ovarectomized group. Four months following the surgical procedures, measurements of estradiol, progesterone, free T4, free T3, and thyroid-stimulating hormone (TSH) were done. Also, estradiol/progesterone and T4/T3 ratios were calculated. Tissue homogenates from the kidney, liver, brain, thyroid, mandible, and femur were used to assess expression of D2 mRNA. The estradiol/progesterone ratio showed a significant increase in ovarectomized rats. T4 showed a significant increase in contrast to T3 which showed a highly significant decrease following ovariectomy. The T4/T3 ratio was significantly increased in ovarectomized rats. In addition, D2 expression was significantly attenuated in all tissue homogenates of the ovarectomized group. The present work showed a H. A. Awad : Z. A. Alrefaie (*) Physiology Department, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia e-mail: [email protected] H. A. Awad Physiology Department, Faculty of Medicine, Ain Shams University, Cairo, Egypt Z. A. Alrefaie Physiology Department, Faculty of Medicine, Cairo University, Cairo, Egypt
significant positive correlation between T4 and T3 in the sham-operated control rats, which was abolished in ovarectomized rats. A negative significant correlation between progesterone and T4 was revealed in ovarectomized rats. There was also a significant positive correlation between progesterone and D2 expression in the ovarectomized group. The results of the present study hypothesize that progesterone withdrawal may underlie the decrement in D2 expression, with consequent reduction in the peripheral conversion of T4 into T3 leading to a hypothyroid state. Keywords Deiodinase 2 . Ovariectomy . Progesterone . Thyroid hormones
Introduction Postmenopausal women are vulnerable to social and health problems. Pearcn stated that the prevalence of thyroid dysfunction increases among women over the age of 50 [11]. In addition, Schindler classified the incidence of thyroid disease in a population of postmenopausal women as clinical thyroid disease, about 2.4 %, and subclinical thyroid disease, about 23.2 %. Among the group with subclinical thyroid disease, 73.8 % were hypothyroid and 26.2 % were hyperthyroid [14]. Formerly, Hernández Valencia et al. postulated a higher frequency of hypothyroidism in aged women and questioned why they do have greater susceptibility [6].
H.A. Awad, Z.A. Alrefaie
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