CIRCULATING CONCENTRATIONS OF THYROID HORMONE IN BELUGA WHALES (DELPHINAPTERUS LEUCAS): INFLUENCE OF AGE, SEX, AND SEASON

Abstract

Thyroid hormones play a critical physiologic role in regulating protein synthesis, growth, and metabolism. To date, because no published compilation of baseline values for thyroid hormones in beluga whales (Delphinapterus leucas) exists, assessment of thyroid hormone concentrations in this species has been underused in clinical settings. The purpose of this study was to document the concentrations of total thyroxine (tT4) and total triiodothyronine (tT3) in healthy aquarium-maintained and free-ranging beluga whales and to determine the influence of age, sex, and season on the thyroid hormone concentrations. Archived serum samples were collected from healthy aquarium-maintained (n=43) and free-ranging (n=39) belugas, and serum tT4 and tT3 were measured using chemiluminescence immunoassay. The mean tT4 concentration in aquarium-maintained belugas was 5.67±1.43 μg/dl and the mean tT3 concentration was 70.72±2.37 ng/dl. Sex comparisons showed that aquarium-maintained males had significantly greater tT4 and tT3 (9.70±4.48 μg/dl and 92.65±30.55 ng/dl, respectively) than females (7.18±2.82 μg/dl and 77.95±20.37 ng/dl) (P=0.004 and P=0.013). Age comparisons showed that aquarium-maintained whales aged 1-5 yr had the highest concentrations of tT4 and tT3 (8.17±0.17 μg/dl and 105.46±1.98 ng/dl, respectively) (P=0.002 and P<0.001). tT4 concentrations differed significantly between seasons, with concentrations in winter (4.59±1.09 μg/dl) being significantly decreased compared with spring (P=0.009), summer (P<0.0001), and fall (P<0.0001) concentrations. There was a significant difference in tT4 and tT3 concentrations between aquarium-maintained whales (5.67±1.43 μg/dl and 70.72±15.57 ng/dl, respectively) and free-ranging whales (11.71±3.36 μg/dl and 103.38±26.45 ng/dl) (P<0.0001 and P<0.001). Clinicians should consider biologic and environmental influences (age, sex, and season) for a more accurate interpretation of thyroid hormone concentrations in belugas. The findings of this study provide a baseline for thyroid health monitoring and comprehensive health assessments in both aquarium-maintained and free-ranging beluga whales.

Effects of breeding center, age and parasite burden on fecal triiodothyronine levels in forest musk deer

“…Thyroid hormones include triiodothyronine (T3), reverse triiodothyronine (rT3), thyroxine (T4), and reverse thyroxine (rT4), and of these the most potent component is T3 [ 3 , 4 ]. Levels of thyroid hormones are affected by several factors, including nutrition [ 5 , 6 ], temperature [ 7 ], age [ 6 , 8 ], sex [ 9 , 10 ], and reproduction [ 8 , 11 ]. Parasite infection poses serious threats to animal health, and creates burdens on the host physiological metabolism [ 12 ].…”

Lipidomics as a diagnostic tool of the metabolic and physiological state of managed whales: A correlation study of systemic metabolism

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Thyroid hormone concentrations associated with age, sex, reproductive status and apparent reproductive failure in the Amazon river dolphin (Inia geoffrensis)

“…Data from both captive and wild healthy populations have enabled researchers to develop models identifying the adverse short- and long-term impacts from this oil spill (Hall et al, 2018; Lane et al, 2015; Smith et al, 2017). Recently, health assessments of wild cetaceans have been applied to an increasing number of marine and freshwater cetacean species (Flower et al, 2015; Nabi et al, 2018; Smith et al, 2017; Van Bressem et al, 2009). Blood and other biological samples collected from animals during these assessments provided the opportunity to examine multiple organ and endocrine systems.…”

“…Blood and other biological samples collected from animals during these assessments provided the opportunity to examine multiple organ and endocrine systems. For cetaceans, overfishing and climate change have elevated the importance of monitoring thyroid function via thyroid hormones to detect critical homeostatic changes in response to these external stressors (Fair et al, 2011; Flower et al, 2015; St. Aubin et al, 1996; Wasser et al, 2017).…”

“…Thyroid hormones have been documented to vary by age and different physiological conditions, e.g. pregnancy and lactation, in multiple mammalian species, including cetaceans (Fair et al, 2011; Flower et al, 2015; St. Aubin, 2001; St.…”