[Long-term critical evaluation of hypothyroidism after subtotal thyroidectomy for thyrotoxicosis]

A retrospective study was made of 66 cases in which subtotal thyroidectomy had been carried for hyperthyroid syndromes, mainly of Basedow type, with a view to establishing a more careful selection of thyrotoxicosis candidates for surgery or other management. The reasons for the different findings and post-operation evaluation of performance are analysed in the light of the time of follow-up, mostly within 5 to 15 yr of surgery. Clinical examination in the light of statistical diagnostic indices was supplemented by evaluation of RIA-T3, TSH and T4, and anti-thyroglobulin antibodies. Four different metabolic states were identified: 1) clinical euthyroidism with normal hormone profile (56.1%); 2) latent hypothyroidism, as shown by high TSH, low T4 and normal RIA-T3 (12.1%); 3) frank hypothyroidism, seen in one case only; 4) high TSH, observed as an isolated finding (30.3%). This last group is fully discussed from the prognostic standpoint. It is not considered as an expression of initial hypothyroidism within the present series and its follow-up range, but as indicative of hypersecretion of an abnormal TSH, or as evidence of an increased hypothalamus-hypophysis axis threshold for the retroactive action of circulating T4 and T3. Attention is drawn to differences between surgical and radio-iodiotherapeutic hypothyroidism. The former, in particular, is less frequent, earlier to appear, and less predictable, whereas the latter displays a gradually increasing pattern.