Patients who have undergone thyroidectomy and radioiodine ablation require lifelong thyroid hormone replacement to prevent hypothyroidism and to minimize TSH stimulation, which promotes tumor growth. However, controversies remain regarding the level of thyrotropin suppression. It seems reasonable to adjust the level of TSH suppression based on the patient's initial clinicopatholo-gic features (103). Thyroid-stimulating hormone levels of 0.1 mU/L or less are usually recommended to minimize the risk of tumor growth; however, treatment with higher doses of thyroid hormone is associated with greater risk of osteoporosis, especially in postmenopausal women. In patients with an undetectable serum Tg concentration and negative neck ultrasound during follow-up, the risk of recurrence is so low that thyroxine doses which maintain TSH levels between 0.1 and 0.5 mU/L are recommended.

The follow-up of thyroid cancer is based on the detection of residual and recurrent thyroid carcinoma. This is traditionally performed by routine palpation and ultrasonography of the thyroid bed and locoregional lymph-node areas, and measurements of serum Tg combined with I-131 whole-body scans after thyroid hormone withdrawal or administration of recombinant TSH (104,105). A low-iodine diet is generally recommended for 7 to 10 days before I-131 administration to enhance the sensitivity for lesion detection. The I-131 whole-body scan may be repeated every year until at least two negative whole-body scans are obtained. The predictive value for 10-year relapse-free survival of one negative I-131 scan is about 90%, whereas two consecutive negative scans have a predictive value greater than 95% (106).

Recently some authors advocate that scanning with I-131 may be discouraged in patients who underwent total thyroidectomy and radioiodine ablation and do not show any clinical evidence of residual tumor or elevated levels of Tg during TSH suppression (107,108). The surveillance of these patients can be performed by using rhTSH-stimulated Tg levels as diagnostic parameter. This is still a matter of debate, because it does not seem valid for all risk groups and not all patients undergo the same clinical management.

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