Prediction of hypothyroidism after partial thyroidectomy for thyrotoxicosis

Hypothyroidism is one of the major complications after thyroidectomy for thyrotoxicosis, but the factors responsible are not well defined. In an attempt to define these factors 278 patients operated on in 1965-9 were studied in detail. The overall incidence of hypothyroidism was 49%. The high incidence of hypothyroidism during 1965-6 led to a policy of leaving larger remnants in the later years of the study, and it became apparent that the most important aetiological factor in postoperative hypothyroidism was small remnant size. There seemed to be an association between the incidence of hypothyroidism and the presence of antithyroglobulin antibodies, but this association was not statistically significant. The data suggested that blood group O might be more common and blood group A less common in hypothyroid patients. The incidence of hypothyroidism seemed to be uninfluenced by the age or sex of the patient, the size of the gland, or the amount and duration of preoperative antithyroid drug therapy.Though a reasonable prediction of the incidence of hypothyroidism can be made for a group of patients on the basis of remnant size, the fate of the individual can be predicted only within very wide limits. An indication of the future status of the individual patient at one year and subsequently does, however, seem possible from serum protein-bound iodine estimations at one and four months after operation. Hypothyroidism developing later than one year after operation has not been observed in this series. The ability to assess thyroid status early after surgery is of some merit in the long-term supervision of the postoperative thyrotoxic patient, and in this respect surgical treatment seems to have some advantage over radioiodine therapy.