We examined biomarkers of selenium status (whole blood Se, serum Se, and glutathione peroxidase activity) and thyroid status (concentrations and ratios of thyroxine, T4, and tri-iodothyronine, T3, and albumin) in polar bears to assess variations among cohorts, and relationships to circulating concentrations of contaminants. Concentrations of total mercury (Hg) in whole blood were similar among cohorts (prime aged males and females, older animals ages ≥ 16 years, and young animals ages 1 – 5 years; 48.44 ± 35. 81; p = 0.253). Concentrations of sum of seven polychlorinated biphenyls (ΣPCB7) in whole blood were greater in females (with and without cubs, 26.44 ± 25.82 ng/g ww) and young (26.81 ± 10.67 ng/g ww) compared to males (8.88 ± 5.76 ng/g ww, p < 0.001), and significantly related to reduced body condition scores (p < 0.001). Concentrations of Se and albumin were significantly greater in males than females (whole blood Se, males, 42.34 pmol/g ww; females, 36.25 ± 6.27 pmol/g ww, p = 0.019; albumin, males, 4.34 ± 0.34 g/dl, females, 4.10 ± 0.29 g/dL, p = 0.018). Glutathione peroxidase activity ranged from 109.1 – 207.8 mU/mg hemoglobin, but did not differ significantly by sex or age (p > 0.08). Thyroid hormones were greater in females (solitary females and females with cubs) compared to males (p < 0.001). Biomarkers of Se status and concentrations of T3 were significantly positively related to Hg in all prime aged polar bears (p < 0.03). Albumin concentrations were significantly positively related to total TT4, and significantly negatively related to concentrations of ΣPCB7 (p < 0.003). Total thyroxine (TT4) was significantly negatively associated with blood concentrations of ΣPCB7 in solitary females (p = 0.045). These data suggest that female polar bears were more susceptible to changes in blood-based biomarkers of selenium and thyroid status than males. Further classifications of the physiologic states of polar bears and repeated measures of individuals over time are needed to accurately assess the biological impact of combined toxicant exposures.

The purpose of the study reported here was to validate measurement of free thyroxine (fT 4 ) concentration in equine serum by equilibrium dialysis (fT 4 D), and to compare values with fT 4 concentration measured directly and with total T 4 (TT 4 ) concentration. The fT 4 D, fT 4 , and TT 4 concentrations were measured over a range of values in euthyroid horses and horses made hypothyroid by administration of propylthiouracil (PTU). Concentrations of fT 4 D (,1.8-83 pmol/L) were consistently higher than those of fT 4 (,1-40 pmol/L). There was a significant (P , .001) regression of fT 4 D on fT 4 in 503 samples from normal horses (y 5 2.086x 2 0.430). In baseline samples from 71 healthy euthyroid horses, fT 4 concentration ranged from 6-21 pmol/L (median, 11 pmol/L; 95% confidence interval [CI]10.5-11.8 pmol/L), and fT 4 D concentration ranged from 7-47 pmol/L (median, 22 pmol/L; 95% CI 20.9-25.1 pmol/L). Free T 4 D, fT 4 , and TT 4 concentrations were also measured in 34 ill horses. Horses consuming PTU and ill horses had significantly (P , .05) lower serum concentration of TT 4 , fT 4 , and fT 4 D than did clinically normal, healthy horses. If serum samples from ill horses were further subdivided into samples from horses that lived and samples from horses that died, fT 4 D concentration was not significantly different in ill horses that lived, compared with that in healthy horses, whereas fT 4 concentration was still significantly decreased in ill horses that died (P , 0.001). We conclude that measurement of fT 4 concentration by equilibrium dialysis is a valid technique in the horse, and its use may provide improved ability to distinguish nonthyroidal illness syndrome from hypothyroidism in that species.

Ten Chesapeake Bay retriever (CBRS) dogs with hair loss were recruited in collaboration with the American Chesapeake Club. All dogs had nonpruritic, noninflammatory, regionalized hair loss affecting the same areas of the body in male and female dogs. Hormonal investigations showed increased adrenal and sex steroid concentration in seven cases. Histopathology revealed follicular hyperkeratosis and plugging, follicular atrophy, and occasional melanin clumping with malformed hair shafts. This study suggests that hair loss in CBRS is a breed syndrome in which young adult dogs have hair loss characterized by unusual histological features and abnormal steroid production. A familial predisposition seems likely and selective breeding might reduce the occurrence of this condition.

The purpose of the study reported here was to validate measurement of free thyroxine (fT4) concentration in equine serum by equilibrium dialysis (fT4D), and to compare values with fT4 concentration measured directly and with total T4 (TT4) concentration. The fT4D, fT4, and TT4 concentrations were measured over a range of values in euthyroid horses and horses made hypothyroid by administration of propylthiouracil (PTU). Concentrations of fT4D (<1.8-83 pmol/L) were consistently higher than those of fT4 (<1-40 pmol/L). There was a significant (P < .001) regression of fT4D on fT4 in 503 samples from normal horses (y = 2.086x - 0.430). In baseline samples from 71 healthy euthyroid horses, fT4 concentration ranged from 6-21 pmol/L (median, 11 pmol/L; 95% confidence interval [CI]10.5-11.8 pmol/L), and fT4D concentration ranged from 7-47 pmol/L (median, 22 pmol/L; 95% CI 20.9-25.1 pmol/L). Free T4D, fT4, and TT4 concentrations were also measured in 34 ill horses. Horses consuming PTU and ill horses had significantly (P < .05) lower serum concentration of TT4, fT4, and fT4D than did clinically normal, healthy horses. If serum samples from ill horses were further subdivided into samples from horses that lived and samples from horses that died, fT4D concentration was not significantly different in ill horses that lived, compared with that in healthy horses, whereas fT4 concentration was still significantly decreased in ill horses that died (P < 0.001). We conclude that measurement of fT4 concentration by equilibrium dialysis is a valid technique in the horse, and its use may provide improved ability to distinguish nonthyroidal illness syndrome from hypothyroidism in that species.

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