The Relationship Between Dermatological Problems And Serum Zinc And Copper Levels In Experimentally Induced Hypothyroidism In Dogs

Abstract

This study was aimed at determining whether or not there was any relationship between dermatological signs and serum zinc (Zn) and copper (Cu) levels in experimentally induced hypothyroidism in dogs. Hypothyroidism was induced by administering methimazole (Thyromazol®) at a dose of 30 mg/kg for 45 days to 20 dogs (11 female and nine male) aged 2-6 years. Serum thyroxin (T4) and triiodothyronine (T3) levels were determined by ELISA, while serum Zn and Cu levels were measured with a Shimadzu Atomic Absorption Spectrophotometer (AA-680) before and after administration of the drug on days 15, 30 and 45. Dogs whose T4 level was lower than 1.8 µg/dl on day 45 of the study were considered as hypothyroidism cases. Histopathological examination was performed using 5 mm punch biopsy samples taken from skin lesioned area on day 45 of the study. The histopathological examination yielded the following results: orthokeratotic hyperkeratosis, atrophy of the epidermis, epidermal melanosis, keratosis, dilatation of the apocrine gland, atrophy and telogenization in follicles, alopecia and pyoderma. Before the administration of the drug and on day 30 and 45 after administration of the drug, the serum T4 levels were found to be significant with p<0.05 and p<0.01 respectively. Serum Zn level had decreased, Cu level had increased but these changes were not statistically significant. Hypothyroidism, one of the most important endocrinopathies observed in dogs, is accompanied by dermatological signs. Those signs, however, were found not be related to zinc deficiency or a copper increase due its antagonist effect. Nonetheless, we are of the opinion that it would be beneficial to add them as premix to the dogs\' diet because of secondary symptoms and their catalytic effects.

Keywords: Hypothyroidism, serum T₄, T₃, Zn, Cu levels, dogs.

Tropical Veterinarian Vol. 23 (3 &4) 2005: pp. 83-86