Hypothyroidism is often an unrecognized sequela of hemithyroidectomy. The purpose of this study was to determine the incidence, risk factors and management of hypothyroidism occurring after hemithyroidectomy for nodular thyroid disease.


All euthyroid patients who underwent hemithyroidectomy from 1992 to 1999 were evaluated for age, sex, preoperative and postoperative serum thyroid-stimulating hormone (TSH) levels, pathology and follow-up. Time of diagnosis and therapeutic doses of thyroid hormone were determined for patients with hypothyroidism. Patients who underwent completion thyroidectomy and those who were on thyroid hormone before operation for TSH suppression or after operation for prevention of recurrent disease were excluded.


During the study period, 70 euthyroid patients underwent hemithyroidectomy. Postoperative hypothyroidism was diagnosed in 25 (36 per cent) with a mean(s.d.) TSH level of 8·51(6·53) (units l−1). Hypothyroidism was subclinical in 16 and overt in nine patients. There were no significant sex or age differences between hypothyroid and euthyroid patients. The mean(s.d.) preoperative serum TSH level was 1·94(1·00) (units l−1) in patients diagnosed with postoperative hypothyroidism compared with 1·08(0·75) (units l−1) in euthy-roid patients (P < 0·05). Associated lymphocytic thyroiditis was present in ten of 25 hypothyroid patients compared with ten of 45 euthyroid patients (P > 0·05). Nineteen patients received thyroid hormone treatment in doses varying from 0·5 to 1·9 (mean 1·3) g kg−1. Follow-up varied from 1 month to 7 years (mean 1 year). All but one hypothyroid patient was diagnosed within 2 months of surgery.


Postoperative hypothyroidism occurs in 36 per cent of patients following hemithyroidectomy. It is usually asymptomatic, and can be diagnosed early after surgery. Hypothyroid patients have higher preoperative TSH levels than euthyroid patients and treatment is accomplished with lower than normal replacement doses of thyroid hormone. © 2000 British Journal of Surgery Society Ltd