Inherited defects of thyroglobulin synthesis resulting in congenital goiter are well described in certain breeds of domestic ungulates and in human beings. Goiter associated with synthesis of an abnormal thyroglobulin and the presence of thyroidal albumin was identified in five closely related bongo antelopes (Tragelaphus eurycerus). The goiter had an adult onset, and the affected bongos appeared to remain euthyroid with normal serum T3 and T4 values, normal serum cholesterol concentrations, and nonelevated concentrations of circulating thyroid stimulating hormone (TSH). Goitrous bongos had significant reproductive difficulties, including reduced cyclic activity and prolonged gestations, but were otherwise normal. Over the course of the disease, the thyroid glands greatly enlarged (up to 10 x 20 cm) and became polycystic. Microscopically, there was an admixture of giant colloid-filled follicles and follicles of normal size lined with variable follicular epithelium ranging from squamoid to mildly to moderately hyperplastic. The pathogenesis of goiter in the bongo may reflect a mixture of genetic predisposition coupled with environmental factors, including a period of exposure to a goitrogen.
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