A case of resistance to thyroid hormone diagnosed after total thyroidectomy for thyroid cancer

This is a case of a woman who was diagnosed with resistance to thyroid hormone after total thyroidectomy for thyroid cancer. Preoperative laboratory examination revealed the syndrome of inappropriate secretion of TSH, however, the patient had no thyrotoxic symptoms and no family history. Based on the results of ultrasonography and fine needle aspiration, she was diagnosed with papillary thyroid carcinoma and underwent total thyroidectomy. After the surgery, she received L-T4 therapy, but her TSH levels remained elevated. MRI was performed on the brain, but no lesions were found in the pituitary gland. Therefore, she was tested for TRβ gene, and a previously defined mutation, P453S, was detected. Ultimately, she was diagnosed as RTH and treated with L-T4. In this case, the dose of L-T4 needed to be increased to suppress her TSH levels to the normal range or less, and to prevent stimulating malignant cells. Currently, her dose of L-T4 has been increased, and her TSH levels are still lower than normal, however, she has no thyrotoxic symptoms, recurrence or metastasis of thyroid cancer. The patient is currently under careful observation regarding her circulatory and physiological status. In addition, the results of treatment still need to be monitored and evaluated.