Low-dose Radioiodine Ablation in Graves' Disease
Condition: Thyroid Diseases
MeSH terms: Graves Disease; Thyroid Diseases
Study type: Observational

Summary: 
      Graves' orbitopathy (GO) is an autoimmune condition almost always associated with autoimmune
      thyroid disease, especially Graves' disease (GD). According to the most widely accepted
      model, the autoantigen/s responsible for GO would include molecules expressed by thyroid
      epithelial cells that are present also in orbital tissues. The high likelihood that the
      etiologies of GO and of the underlying autoimmune thyroid diseases are somehow linked is
      confirmed by the very close relationship between GO, the onset and the course of Graves'
      diseases, the size of the thyroid gland, and most importantly, thyroid function and thyroid
      treatment. Based on these considerations, it has been proposed that complete removal of
      thyroid antigens and of thyroid infiltrating lymphocytes, the so called total thyroid
      ablation (TTA), may be followed by an attenuation of the immune reaction against orbital
      antigens, and ultimately by an amelioration of GO. The possibility that TTA, achieved by near
      total thyroidectomy followed by radioiodine, may be beneficial for GO was initially suggested
      by two retrospective studies and more recently by two prospective, randomized clinical trials
      conducted in patients with moderate GO treated with intravenous glucocorticoids. Although
      there seemed to be no difference in the long term, compared with near total thyroidectomy
      alone TTA was associated with a shorter time required for GO to improve, or anyway to reach
      its best possible outcome, and with a lesser requirement for additional treatments in order
      for GO to improve.

      TTA is usually performed with a radioiodine dose of 30 millicurie (mCi), administered after 2
      injections of recombinant human thyrotropin TSH (rhTSH), the latter in order to induce
      radioiodine uptake by thyroid remnants. According to the Italian legislation the
      administration of such a dose of radioiodine must be followed by a 24 hours protected
      hospitalization. Clearly, this necessity implies a remarkable increase of the waiting list,
      due to the limited number of radiation-isolated beds available and, concerning GO patients,
      to the competition with patients with thyroid cancer. In contrast, a radioiodine dose of 15
      mCi can be performed in out-patients without hospitalization and with much lower costs.
      Concerning GD patients, they usually have serum TSH-receptor stimulating antibodies that ay
      persist after thyroidectomy and that may increase radioiodine uptake along with rhTSH,
      possibly resulting in the need for a lower dose of radioiodine to ablate thyroid remnants. In
      order to investigate whether this is the case, the present study was designed in patients
      with GD. The study design was to include patients scheduled to radioiodine treatment with 30
      or 15 mCi after administration of rhTSH, being the primary outcome the values of serum
      thyroglobulin at peak after administration of rhTSH 6 months after radioiodine, as a measure
      of the presence of residual thyroid tissue.
    


Intervention name(s): Radioiodine
Intervention type(s): Radiation
Intervention description(s): Administration of radioiodine
Other intervention name(s): 131-Iodine
Observational model: Case-Control
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Thyroidectomized patients with Graves' hyperthyroidism and GO undergoing radioiodine
        ablation with either 15 or 30 mCi of 131I