Abstract
Objective—To assess changes in serum concentrations of thyroid hormones associated with selenium deficiency myopathy in lambs.
Animals—35 lambs with selenium deficiency myopathy and 30 healthy lambs.
Procedures—Blood samples were collected via jugular venipuncture from lambs with selenium deficiency myopathy and healthy lambs. Activities of markers of selenium deficiency myopathy (erythrocyte glutathione peroxidase [GSH-Px] and plasma creatine kinase [CK]) and serum thyroid-stimulating hormone (TSH) and total thyroxine (tT4) and total triiodothyronine (tT3) concentrations were assessed; values in affected lambs were compared with those in healthy lambs. Correlations of erythrocyte GSH-Px and plasma CK activities with serum concentrations of TSH, tT4, and tT3 were investigated, and the tT3:tT4 concentration ratio was evaluated.
Results—Compared with findings in healthy lambs, erythrocyte GSH-Px activity, serum tT3 concentration, and tT3:tT4 concentration ratio were significantly decreased and serum concentrations of tT4 and TSH and the activity of plasma CK were significantly increased in affected lambs. Analysis revealed a significant negative correlation in the affected group between erythrocyte GSH-Px activity and each of the following: plasma CK activity (r = −0.443), serum TSH concentration (r = −0.599), serum tT4 concentration (r = −0.577), and serum tT3 concentration (r = −0.621).
Conclusions and Clinical Relevance—Results suggested that notable changes in circulating amounts of thyroid hormones develop in association with selenium deficiency in lambs. Such alterations in thyroid hormone metabolism may be involved in the high incidence of disorders, such as stillbirths and neonatal deaths, in selenium-deficient flocks.
