Abstract
The purpose of this study was to investigate thyroid hormone concentrations, thyroxine (T 4) and triiodothyronine (T 3), in order to determine basal levels in Steller sea lions of different ages and over seasons. Serum concentrations of total T 4 were highest in Steller sea lions followed by total T 3 concentrations. Concentrations of free T 4 and free T 3 were three to four orders of magnitude lower. Concentrations for all four thyroid hormone measurements tended to a lower level as animals matured beyond the neonatal stage. When thyroid hormones from captive sea lions were evaluated across seasons, all thyroid hormones were highest in the July to September period. When compared across the geographic range, animals in southeast Alaska tended to have lower thyroid hormone levels, while the Steller sea lions west of Prince William Sound and animals from the Russian Far East had significantly higher concentrations. Significant inter-annual differences in concentrations were also observed across the geographic range. With an understanding of the basic changes in thyroid hormone concentrations, changes in plane of nutrition or life history states (i.e. fasting, pregnancy or lactation) can now be evaluated for their effect on the overall health of this endangered species.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
