Differential effects of propylthiouracil, methimazole and thyroidectomy on liver ferritin

Different groups of rats were made hypothyroid by thyroidectomy (Tx) or treatment with propylthiouracil (PTU) or methimazole (MMI). Some of the hypothyroid rats from each group were simultaneously treated with thyroxine (T4). Liver ferritin concentration and 14C-glycine incorporation into liver ferritin in these rats were studied. Only in MMI-treated rats the ferritin concentration was elevated, which was reduced by simultaneous T4 treatment. PTU treatment resulted in 36-42% reduction in ferritin synthesis, which was not responsive to T4. Thyroidectomy induced 23% enhancement in ferritin synthesis, which was normal in T4-treated Tx rats. The possible causes for these differential effects in hypothyroid rats have been discussed.