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Changes in glucocorticoids, IGF-I and thyroid hormones as indicators of nutritional stress and subsequent refeeding in Steller sea lions (Eumetopias jubatus)

TitleChanges in glucocorticoids, IGF-I and thyroid hormones as indicators of nutritional stress and subsequent refeeding in Steller sea lions (Eumetopias jubatus)
Publication TypeJournal Article
Year of Publication2009
AuthorsDot, TJeanniard, Rosen, DAS, Richmond, JP, Kitaysky, AS, Zinn, SA, Trites, AW
JournalComparative Biochemistry and Physiology
VolumePart A152
Pagination524–534
Abstract

Physiological responses to changes in energy balance are tightly regulated by the endocrine system throughglucocorticoids, IGF-I and thyroid hormones. Changes in these hormones were studied in eight captivefemale Steller sea lions that experienced changes in food intake, body mass, body composition, and bloodmetabolites during summer and winter. During a period of energy restriction, one group of sea lions was fedreduced amounts of Pacific herring and another was fed an isocaloric diet of walleye pollock, after whichboth groups returned to their pre-experimental diets of herring. Cortisol was negatively and IGF-I waspositively associated with changes in body mass during periods of energy restriction (mass loss associatedwith increase in cortisol and decrease in IGF-I) and refeeding (body mass maintenance associated with stablehormone concentrations in summer and compensatory growth linked to decrease in cortisol and increase inIGF-I in winter). Cortisol and IGF-I were also correlated with changes in lipid and lean mass, respectively.Consequently, these two hormones likely make adequate biomarkers for nutritional stress in sea lions, andwhen combined provide indication of the energetic strategy (lipid vs lean mass catabolism) animals adopt tocope with changes in nutrient intake. Unlike type of diet fed to the sea lions, age of the animals also impactedhormonal responses, with younger animals showing more intense hormonal changes to nutritional stress.Thyroid hormones, however, were not linked to any physiological changes observed in this study

DOI10.1016/j.cbpa.2008.12.010
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