Plasma concentrations of thyroid hormones in a captive and feral polar bear (Ursus maritimus)

Blood-based biomarkers of selenium and thyroid status indicate possible adverse biological effects of mercury and polychlorinated biphenyls in Southern Beaufort Sea polar bears

“…Although highly variable, the mean of total T4 concentration of polar bears in the present study (mean, 15 nmol/l) was three times lower than previously reported for presumably healthy captive and free-ranging polar bears (TT4, 50 nmol/l), although TT3 concentrations (present study, mean 1.4 nmol/l) were similar (TT3, 1.5 nmol/l; Churchill, Canada, Leatherland and Ronald 1981). Thyroid hormone concentrations of SBS polar bears were also lower than normal values for humans (TT4, 103 nmol/l; TT3, 2.3 nmol/l; Ganong 2001).…”

“…Greater thyroid hormone concentrations in females versus males are common among vertebrates, including polar bears, and suspected to relate to the regulation and interaction with estrogens (Braathen et al 2004; Leatherland and Ronald 1981; Norris 2006; Skaare et al 2001). Biological responses to toxicants in female polar bears would be expected to be more complex than males as females experience different physiologic and homeostatic states during spring such as recent fasting, lactation, caring for young, breeding activities, and estrous.…”

Blood-based biomarkers of selenium and thyroid status indicate possible adverse biological effects of mercury and polychlorinated biphenyls in Southern Beaufort Sea polar bears

“…Although highly variable, the mean of total T4 concentration of polar bears in the present study (mean, 15 nmol/l) was three times lower than previously reported for presumably healthy captive and free-ranging polar bears (TT4, 50 nmol/l), although TT3 concentrations (present study, mean 1.4 nmol/l) were similar (TT3, 1.5 nmol/l; Churchill, Canada, Leatherland and Ronald 1981). Thyroid hormone concentrations of SBS polar bears were also lower than normal values for humans (TT4, 103 nmol/l; TT3, 2.3 nmol/l; Ganong 2001).…”

“…Greater thyroid hormone concentrations in females versus males are common among vertebrates, including polar bears, and suspected to relate to the regulation and interaction with estrogens (Braathen et al 2004; Leatherland and Ronald 1981; Norris 2006; Skaare et al 2001). Biological responses to toxicants in female polar bears would be expected to be more complex than males as females experience different physiologic and homeostatic states during spring such as recent fasting, lactation, caring for young, breeding activities, and estrous.…”

Relationships between PCBs and thyroid hormones and retinol in female and male polar bears.

“…This result agrees with previous studies of THs in polar bears (Leatherland and Ronald 1981;Skaare et al 2001). However, in polar bears captured in Resolute Bay in the Canadian Arctic, only T 3 levels were significantly higher in females than in males (Sandau 2000).…”

“…found in the present study have been reported (Leatherland and Ronald 1981;Sandau 2000). Because knowledge of normal baseline TH plasma levels in polar bears is very sparse, it is not possible to judge whether any of the polar bears in the present study suffered from hypothyroidism.…”

The Ought-Ecology of Ferals: An Emerging Dialogue in Invasion Biology and Animal Studies

“…When feral is used to describe behaviour, it usually applies to a specific population (often monkeys) or individuals (a rogue polar bear in Churchill, Manitoba) who are behaving unnaturally or causing risk for humans. In the case of the feral polar bear, it was in its natural habitat, but its behaviour had altered in response to the presence of humans and towns (Leatherland and Ronald 1981). These bears are typically found 'in the dump, in town, damaging property, and/or threatening life' and are now more correctly identified as 'problem' bears (Towns et al 2009).…”

Blood-based biomarkers of selenium and thyroid status indicate possible adverse biological effects of mercury and polychlorinated biphenyls in Southern Beaufort Sea polar bears

“…Although highly variable, the mean of total T4 concentration of polar bears in the present study (mean, 15 nmol/l) was three times lower than previously reported for presumably healthy captive and free-ranging polar bears (TT4, 50 nmol/l), although TT3 concentrations (present study, mean 1.4 nmol/l) were similar (TT3, 1.5 nmol/l; Churchill, Canada, Leatherland and Ronald 1981). Thyroid hormone concentrations of SBS polar bears were also lower than normal values for humans (TT4, 103 nmol/l; TT3, 2.3 nmol/l; Ganong 2001).…”

“…Greater thyroid hormone concentrations in females versus males are common among vertebrates, including polar bears, and suspected to relate to the regulation and interaction with estrogens (Braathen et al 2004; Leatherland and Ronald 1981; Norris 2006; Skaare et al 2001). Biological responses to toxicants in female polar bears would be expected to be more complex than males as females experience different physiologic and homeostatic states during spring such as recent fasting, lactation, caring for young, breeding activities, and estrous.…”

Relationships between PCBs and thyroid hormones and retinol in female and male polar bears.

“…This result agrees with previous studies of THs in polar bears (Leatherland and Ronald 1981;Skaare et al 2001). However, in polar bears captured in Resolute Bay in the Canadian Arctic, only T 3 levels were significantly higher in females than in males (Sandau 2000).…”

“…found in the present study have been reported (Leatherland and Ronald 1981;Sandau 2000). Because knowledge of normal baseline TH plasma levels in polar bears is very sparse, it is not possible to judge whether any of the polar bears in the present study suffered from hypothyroidism.…”

The Ought-Ecology of Ferals: An Emerging Dialogue in Invasion Biology and Animal Studies

“…When feral is used to describe behaviour, it usually applies to a specific population (often monkeys) or individuals (a rogue polar bear in Churchill, Manitoba) who are behaving unnaturally or causing risk for humans. In the case of the feral polar bear, it was in its natural habitat, but its behaviour had altered in response to the presence of humans and towns (Leatherland and Ronald 1981). These bears are typically found 'in the dump, in town, damaging property, and/or threatening life' and are now more correctly identified as 'problem' bears (Towns et al 2009).…”

Blood-based biomarkers of selenium and thyroid status indicate possible adverse biological effects of mercury and polychlorinated biphenyls in Southern Beaufort Sea polar bears

“…Although highly variable, the mean of total T4 concentration of polar bears in the present study (mean, 15 nmol/l) was three times lower than previously reported for presumably healthy captive and free-ranging polar bears (TT4, 50 nmol/l), although TT3 concentrations (present study, mean 1.4 nmol/l) were similar (TT3, 1.5 nmol/l; Churchill, Canada, Leatherland and Ronald 1981). Thyroid hormone concentrations of SBS polar bears were also lower than normal values for humans (TT4, 103 nmol/l; TT3, 2.3 nmol/l; Ganong 2001).…”

“…Greater thyroid hormone concentrations in females versus males are common among vertebrates, including polar bears, and suspected to relate to the regulation and interaction with estrogens (Braathen et al 2004; Leatherland and Ronald 1981; Norris 2006; Skaare et al 2001). Biological responses to toxicants in female polar bears would be expected to be more complex than males as females experience different physiologic and homeostatic states during spring such as recent fasting, lactation, caring for young, breeding activities, and estrous.…”

Relationships between PCBs and thyroid hormones and retinol in female and male polar bears.

“…This result agrees with previous studies of THs in polar bears (Leatherland and Ronald 1981;Skaare et al 2001). However, in polar bears captured in Resolute Bay in the Canadian Arctic, only T 3 levels were significantly higher in females than in males (Sandau 2000).…”

“…found in the present study have been reported (Leatherland and Ronald 1981;Sandau 2000). Because knowledge of normal baseline TH plasma levels in polar bears is very sparse, it is not possible to judge whether any of the polar bears in the present study suffered from hypothyroidism.…”

The Ought-Ecology of Ferals: An Emerging Dialogue in Invasion Biology and Animal Studies

“…When feral is used to describe behaviour, it usually applies to a specific population (often monkeys) or individuals (a rogue polar bear in Churchill, Manitoba) who are behaving unnaturally or causing risk for humans. In the case of the feral polar bear, it was in its natural habitat, but its behaviour had altered in response to the presence of humans and towns (Leatherland and Ronald 1981). These bears are typically found 'in the dump, in town, damaging property, and/or threatening life' and are now more correctly identified as 'problem' bears (Towns et al 2009).…”