Akademik Veri Yönetim Sistemi
REVUE DE MEDECINE VETERINAIRE, cilt.155, sa.6, ss.324-330, 2004 (SCI-Expanded)
The aim of the present study was to determine the effects of different oral doses of prednisolone (classically used during anti-inflammatory and immunosuppressive therapies with decreasing and/or alternate day protocol scheme) on the serum triiodothyronine (T-3), thyroxine (T-4) and free T-4 (fT(4)) concentrations and thyroid gland morphology. Prednisolone was given orally at gradually decreased doses, from 1.1 mg kg / day to 1.1 mg / kg / alternate day for 21 days in group I (n = 8) and from 2.2 mg / kg / day to 0.25 mg / kg / day for 50 days in group II (n = 7). Serum samples were obtained from treated mixed breed dogs before treatment, after each dose reduction and 15 days after the end of treatment. Seven dogs (group III) served as controls. Thyroid biopsies were surgically obtained on days 22 and 37 in group I, on days 51 and 66 in group II and on days 22 and 51 in group III. With prednisolone high doses, early decreases of serum T-3 and fT(4) concentrations (p < 0.05) were obtained in group I (on day 8) and in group II (on day II). The alteration of thyroid function has persisted until the 21(st) day with low T-3, T-4 and fT(4) concentrations in group II. As soon as doses were markedly reduced, hormone concentrations significantly increased for reaching even overtaking pre-treatment values fifteen days after the end of treatments. Light and electron microscopic examinations revealed that inactive follicle areas were seen among the active follicle areas in both treatment groups, especially in group II. Despite the increase in the number of the colloid droplets, less or no lyzosomes were seen in follicle epithelial cells in treated groups. Thyroid glands recovered normal appearance within 15 days post-treatment. In conclusion, gradually decreased and/or alternated doses of prednisolone, used in anti-inflammatory and immunosuppressive therapies caused transient changes not only in serum T-3, T-4 and fT(4) concentrations, but also in thyroid morphology (although changes were more prolonged) and allowed relevant adaptative mechanisms to occur.