Subtotal thyroidectomy for thyrotoxicosis: a reassessment, including TRH responsiveness

Thyroid function was assessed in patients treated surgically for thyrotoxicosis in Christchurch between 1965 and 1972. Seventy-eight of the 89 thyrotoxic patients were available for reassessment. Seventy-one were clinically and biochemically euthyroid. Seven patients had received radioiodine therapy for post-operative relapse and 10 patients were receiving thyroxine replacement therapy. At the time of the survey five patients were clinically thyrotoxic and two patients were hypothyroid and an additional nine patients had grossly elevated TSH levels. TRH tests performed on 31 clinically euthyroid patients with normal baseline thyroid parameters demonstrated that more than a third had excessive TSH responses consistent with reduced thyroid reserve and only one patient showed a lack of response consistent with persistent thyroid autonomy.