Impaired local deiodination of thyroxine to triiodothyronine in dogs with symmetrical truncal alopecia

Thyroid dysfunction causes certain dermatological alterations in dogs. Insufficient delivery of thyroid hormone to the skin may originate not only from inadequate thyroid function but also from impaired local activation of thyroxine in the target organ. Thyroid parameters and deiodination were investigated in healthy dogs (group C) and in dogs with cutaneous lesions associated with hypothyroidism (group H) or with a low-T₃ syndrome (group LT). The ability of the skin to convert T₄ to T₃ was impaired in both groups H and LT but not in the controls. It is concluded that impaired local deiodination may contribute to skin problems in dogs.Abbreviations bwt body weight - DTT dithiothreitol - PBS phosphate-buffered saline (pH 7.5, 0.05 mol/L) - PTU propylthiouracyl - RIA radioimmunoassay - TRH thyrotropin-releasing hormone - TSH thyroid-stimulating hormone