Alopecia difusa e atrofia da tireoide associadas à deficiência de selênio e zinco em ovinos.

Abstract

Thyroid disorders substantially affect quality of life, as they are associated with a wide range of disorders in different organs. Among the factors that predispose to thyroid dysfunction, studies report that high or low amounts of zinc intake (Zn) and selenium deficiency (Se) may trigger the development of hypothyroidism due to the decrease in the production of hormones produced by the thyroid. Zn and Se deficiency results in direct and indirect cutaneous lesions, both by the action of free radicals on the skin and by thyroid dysfunction. The objective of this study was to describe natural cases of diffuse alopecia and thyroid alterations in sheep with Se and Zn deficiency. Five adult sheep affected by a systemic syndrome associated with alopecia were treated at the Veterinary Hospital. Clinical examinations and blood collection were performed to determine blood serum levels of selenium, zinc and thyroid hormones. Concentrations of total triiodothyronine (T3), total thyroxine (T4), serum levels of selenium and zinc, as well as levels of iron, cobalt, copper, molybdenum, selenium and zinc of the liver were determined. The sheep had pronounced multifocal to coalescent alopecia, with dry and brittle hair. The skin was thick, covered with scabs and with marked scaling. Serum T3 and T4 concentrations were below the reference values. The amount of Zn and Se were low in both serum and liver. Necropsy showed cachexia associated with serous fat atrophy, in addition to marked atrophy of the thyroid gland. Microscopically, the thyroid presented multifocal to coalescent atrophy, atrophied and dilated follicles, infiltration of macrophages and presence of fibrous connective tissue. The skin revealed hyperkeratosis, edema and ectasia of the sweat glands. It is concluded that thyroid disease directly affects the skin as a result of thyroid hormones possessing skin receptors, directly interfering in the biology of the epidermis, dermis and hairs, as well as the importance of mineral supplementation for body homeostasis.