243 Iranian Journal of Veterinary Medicine Iran J Vet Med., Vol 11, No 3 (Summer 2017), Comparison of serum triiodothyronine, tetraiodothyronine and thyroid stimulating hormone concentrations in pregnant and lactating Beetal-cross and native goats in Garmsar township Raoof, A. 1* , Yourdkhani, S. 2 , Bokaie, S. 3 1 Department of Internal Medicine, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran 2 Department of Clinical Sciences, Faculty of Veterinary Medicine, Garmsar Branch, Islamic Azad Universi- ty, Garmsar, Iran 3 Division of Epidemiology and Zoonoses, Department of Food Hygiene and Quality Control, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran Abstract: BACKGROUND: The preliminary survey made about con- genital goiter in goats in Garmsar township indicated that the disease occurs much more in Beetal-cross than native goats raised in the same area. OBJECTIVES: The aim of the present study was to compare serum triiodothyronine (T3), tetraiodothyronine (T4) and thyroid stimulating hormone concentrations in pregnant and lactating Beetal-cross and native goats in Garmsar township. METHODS: One hundred Beetal-cross (n=50) and native (n=50) does in 4 groups (25 pregnant Beetal-cross, 25 lactating Beetal-cross, 25 pregnant native and 25 lactating native) were used in this study. Blood samples were obtained via jugular venipuncture and ana- lyzed for serum T3, T4 and TSH concentrations. RESULTS: Breed had a signifcant (p<0.05) effect on T4 concentration and pregnancy had a signifcant (p<0.05) effect on T3 and TSH concentrations. No signifcant differences were seen for serum T3, T4 and TSH concentrations between preg- nant and lactating native does. However, in the pregnant Beetal-cross, serum T3 and T4 concentrations were lower (p<0.05) and TSH concentration was higher (p<0.05) than lactating Beetal-cross does. CONCLUSIONS: The results of the present study highlight the relationships between thyroid activity and breed in the goat species that may play a role in more occurrence of congenital goiter in Beetal-cross in Garmsar township. Key words: breed, goat, T3, T4, TSH Correspondence Raoof, A. Department of Internal Med- icine, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran Tel: +98(21) 61117164 Fax: +98(21) 669333222 Email: raoof@ut.ac.ir Received: 10 January 2017 Accepted: 3 April 2017 Introduction The thyroid gland is unique in that it is the only tissue of the body which is able to accumulate iodine in large quantities and incorporate it into hormones. The thy- roid hormones, triiodothyronine (T3) and tetraiodothyronine (T4) act on different tar- get tissues, stimulating oxygen utilization and heat production in all types of body cells. The overall effects of these hormones are to increase the basal metabolic rate, to make more glucose available to cells, to stimulate protein synthesis, increase lipid metabolism and to stimulate cardiac and neural functions. Only the thyrotrophin 243-248