Abstract
Stimulation of the thyroid with thyroid-stimulating hormone (TSH) is a potentially useful diagnostic of thyroid dysfunction, but little is known about the response of the thyroid to TSH stimulation in bottlenose dolphins (Tursiops truncatus). To better characterize the response of the dolphin thyroid to TSH stimulation, five adult dolphins participated in a TSH stimulation study. Dolphins voluntarily beached onto a padded mat and were given a 1.5 mg intramuscular injection of human recombinant TSH. Blood samples collected the day prior, at multiple intervals the day of, and daily for three days after the injection were analyzed via radioimmunoassay for free and total triiodothyronine (fT3 and tT3), and free and total thyroxine (fT4 and tT4). Significant increases in circulating fT3, fT4, and tT4 were observed with peaks occurring for all hormones the day after the TSH injection; maximal increases were 44%, 47%, and 23% for each hormone, respectively. Temporal patterns in the hormones potentially reflected feedback mechanisms countering the surge in fT3 following stimulation. Though recombinant human TSH was effective at stimulating hormone release, it is likely that use of dolphin or dolphin-derived TSH would enhance the clinical utility of the stimulation test, as would the development of antibodies specific to dolphin TSH.
Highlights
Proper thyroid function and thyroid hormone regulation are critical for organismal health as thyroid hormones affect nearly every organ system of the body
Individual levels of circulating thyroid hormones were variable between individuals, but all individuals showed an increase in Free T3 (fT3), free T4 (fT4), tT4, and reverse T3 (rT3) following the thyroid stimulation (TS)
West and colleagues [7] were the first to report on the use of human recombinant Thyroidstimulating hormone (TSH) to stimulate the thyroid of a bottlenose dolphin
Summary
Proper thyroid function and thyroid hormone regulation are critical for organismal health as thyroid hormones affect nearly every organ system of the body. Thyroidstimulating hormone (TSH), or thyrotropin, is the primary hormone stimulating thyroid hormone released from the thyroid gland. Produced by the anterior pituitary in response to thyrotropin-releasing hormone (TRH), TSH stimulates the release of triiodothyronine (T3) and thyroxine (T4) from thyroid follicular cells. Regulation can be achieved by converting T4 into reverse T3 (rT3), which is commonly accepted as an end product of T4 degradation and which can weakly compete with T3 in binding to T3 thyroid nuclear hormone receptors. Given the importance of thyroid hormone to organismal health, the study of thyroid hormone production and regulation has received extensive attention within the field of human medicine
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
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
