The purpose of this study was to determine the protective effect of thymoquinone (TQ), curcumin (CUR), and a TQ+CUR combination on thyroid hormones and histopathology in an experimentally-induced, subacute, sodium fluoride (NaF) toxicity rat model. Control, sham, and test groups (NaF, NaF+TQ, NaF+CUR, and NaF+TQ+CUR) were established in the study. At the end of the experiment, test groups had higher urine fluoride concentrations. Triiodothyronine (T3), thyroxin (T4), free triiodothyronine (FT3), and free thyroxin (FT4) levels decreased substantially, and thyroid-stimulating hormone (TSH) levels increased substantially when the control and test groups were compared. T3 and T4 decreased and TSH increased in the NaF group compared to the NaF+TQ, NaF+CUR, and NaF+TQ+CUR groups. Microscopic study of thyroid tissues revealed that the test groups showed statistically significant differences from the control group in terms of follicular degeneration (FD), decrease in colloidal fluid (DCF), fibrosis, atypical follicle epithelium (AFE), and mononuclear cell infiltration (MCI). When the NaF group and other test groups were compared, statistical significance was observed in the histopathological scoring of DCF, AFE, and MCI in the NaF+TQ group; FD, DCF, AFE, and MCI in the NaF+CUR group; and DCF, AFE, and MCI in the NaF+TQ+CUR group. Fluoride toxicity, therefore, caused problems with the thyroid and hormones. The study revealed that TQ and CUR combined with fluoride could not normalize the thyroid gland and thyroid hormones but could alleviate thyroid gland damage and provide a partial improvement in thyroid hormone levels.
"Experientia docet" - Experience is the best teacher