Manganese Ion as a Goitrogen in the Female Mouse

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Effect of excessive ingestion of manganese (Mn) on the mouse thyroid was assessed under the conditions of normal intake of iodide. Female mouse thyroids were enlarged after 7 weeks of administration of 200mg/l MnCl₂·4H₂O in drinking water; 2.74±0.25mg for control (N=56), and 3.31±0.28mg for Mn-treated group (N=85)(p<0.001). In contrast, male mouse thyroids never became goitrous following this treatment. Manganese was goitrogenic to the castrated male mouse, but it had no effect on the testosterone-treated castrated male mouse, indicating the involvement of androgen in goiter formation. Oral administration of Mn did not severely affect blocked T/S of ¹²⁵I or iodine metabolism in the thyroid. A morphological study, however, revealed that the epithelial cell in the Mn-treated mouse thyroid became flatter than that of the control. The lumens were filled with colloid in Mn-treated female mouse thyroid. The serum levels of thyroxine (T₄), but not triiodothyronine (T₃), were slightly reduced by Mn.
These informations suggest that Mn can be a mild goitrogen for the female mouse and that the etiology of goiter formation can be interpreted by retention of colloid in the lumen.