Alterations of circulating cortisol, IGF-1, and thyroid hormones in Darehshori horses during a year

Abstract

Season may be considered as a factor that affects the equine endocrine profile. Hence, from January to November 2015, 27clinically healthy adult Darehshori racehorses were selected. Thirteen of them were stallions and the others were mares. Ten of themwere more than 10 years old and 17 horses were under the age of 10 years. None of them were pregnant or lactating during the study.Body condition scores of 12 horses were below and the others were above 5. Blood samplings and body condition score evaluationswere performed every 45 days during a year. Serum levels of cortisol, IGF-1, T3, T4, and TSH were assayed in all specimens. T3 andTSH were significantly decreased following the warming up of the climate in different ages, sexes, and body condition scores, but therewere no significant changing patterns in T4. There were various trend changes of both cortisol and IGF-1 in different ages, sexes, andbody condition scores during the seasons of the study period. Based on the results, circulating levels of cortisol, IGF-1, and thyroidhormones of Darehshori horses are dependent on many factors such as breed, sex, age, body condition, season, geographical location,and individual characteristics.