Irreversible thyroid disruption induced after subchronic exposure to hexachlorobenzene in male rats

Abstract

Thyroid hormones play a complex role in the toxicity of hexachlorobenzene (HCB) and related compounds. Time-course and dose-response experiments for free- and total thyroxine (T4) and triiodothyronine (T3) plasma levels for thyroid-stimulating hormone (TSH) and thyroid gland histomorphology were determined in male Wistar rats. Also, we examined the possible reversibility of changes noted after removal of HCB. Rats treated with this organochlorine compound resulted in a hypertrophy of the thyroid gland and altered thyroid function by decreasing significantly the levels of total- and free T4 in a dose-dependent manner (total T4: 28 and 51%; free T4: 21 and 37%), and this decrease was seen as early as 21 days and thereafter. Free T3 was also decreased by 21% with the highest dose starting from day 21. No significant changes were observed in the circulating levels of total T3 In response to the decrease of thyroid hormones, a dose-dependent increase of TSH levels (27 and 31%, respectively, for 4 mg and 16 mg/kg of HCB body weight) was observed after 21 days of HCB treatment. We have observed a hypertrophy and hyperplasia of follicular cells and a decrease in colloid volume in histological picture. When HCB was removed and changed by vehicle, the thyroid relative weight and plasma TSH continued to rise and serum thyroid hormones remained suppressed. These findings suggest that subchronic exposure of rats to HCB induced an irreversible hypothyroidism state.

Thyroid-disrupting chemicals and brain development: an update

“…Affected individuals, primarily children, displayed changed porphyrin metabolism, leading to porphyria cutanea tarda , enlarged liver and thyroid gland and osteoporosis ( 192 , 193 ). Similar effects have been observed in HCB-exposed rats ( 194 ) i.e. hepatic and thyroid neoplasms ( 195 , 196 , 197 ), porphyria ( 193 , 198 ).…”

Non-Alcoholic Fatty Liver Disease and Hypothyroidism: Review of Clinical and Experimental Studies

“…Experimental studies play an important role in the determination of morphological alterations or investigation of induced pathological conditions [27]. Thus, Chalouati H et al have found irreversible thyroid changes and hypothyroid state caused by subchronic hexachlorobenzene exposure [28]. According to Jiang LQ et al, amiodarone may affect lipid profile and cause hypothyroidism [29].…”