Thyrotoxicosis--treatment by I131 therapy and early prediction of hypothyroidism following this therapy.

This study was undertaken in 68 thyrotoxic patients to assess the predictive value of various post treatment biochemical and immunological tests for early hypothyroidism after I131 therapy and to determine whether pretreatment with carbimazole protects against post I131 therapy hypothyroidism. Early changes observed in serum T3, T4, TSH, thyroid microsomal and thyroglobulin antibody levels were found to be of no predictive value. A sharp increase in TRAb levels around 3 months following I131 therapy indicated that hypothyroidism was likely to occur as this rise reflected a greater degree of thyroid damage. Lower levels of thyroglobulin in patients who became hypothyroid by 12 months after treatment would support this view. Carbimazole pretreatment for eight weeks did not appear to protect against hypothyroidism, in our study.