Treatment of diffuse toxic goiter with 131I

Abstract

The treatment of diffuse toxic goiter with 131 I is reviewed. Consideration is given to appropriate selection of patients for radioiodine therapy, as well as to the indications and contraindications for this therapy. Methods of calculating radioiodine dose are presented. However, it must be emphasized that results of therapy cannot be correlated with the method of dose calculation, but, more importantly, they are closely aligned with the amount of radiation actually administered to the thyroid. Recently suggested protocols employing low doses of radioiodine appear to give rise to a lowered incidence of hypothyroidism soon after therapy; however, as is the case with higher doses of radioiodine and surgery, hypothyroidism still appears to increase with time. Since lower doses of radioiodine also are associated with persisting manifestations of the disease, adjunctive drug therapy in the form of propranolol is necessary. The major undesirable longterm effect of radioiodine appears to be hypothyroidism. When radioiodine is used in patients over 20 yr of age, thyroid cancer and leukemia have not appeared as post-therapeutic problems. Because of the unsatisfactory and speculative nature of all forms of therapy for Graves' disease, new approaches are required. To promote some productive discussion in this area, the following three-point hypothesis is presented: (1) The thyroid gland is made up of functioning (follicular) cells and stem cells. (2) The functioning cells are long-lived and radio-resistant, but Graves' disease and radiation decrease their natural longevity. (3) The thyroid stem cells are quite sensitive to radiation and differ little from other mammalian stem cells (LD 37 equal to about 100 to 150 rads).