Background: Lobectomy with preservation of the contralateral lobe has already become the most preferred surgical method for patients with low-risk
thyroid cancer. The incidence of and risk factors for the development of
hypothyroidism after lobectomy for
thyroid cancer remains unclear. The previous practice of
levothyroxine supplementation post-
thyroidectomy, to bring about
thyroid stimulating hormone (TSH) suppression, had some serious side effects. This study aimed to evaluate the incidence of
hypothyroidism and to identify the factors associated with
hypothyroidism requiring
thyroid hormone replacement. Methods: We retrospectively reviewed the charts of 256 consecutive patients with differentiated
thyroid cancer treated with lobectomy at the Gangnam Severance Hospital between April and December 2014 who were followed-up for more than 5 years. Patients were evaluated using a thyroid function test at the time of outpatient visit every 6 months for the 1st year, with an annual follow-up thereafter. Results: After 5 years, 66.0% (169) of the patients needed
levothyroxine supplementation to maintain euthyroid status. The incidence of
hypothyroidism requiring
levothyroxine supplementation increased until 3 years but showed no significant change in the 4 and 5th year. Recurrence showed no difference between the group with and without
levothyroxine supplementation. The presence of
thyroiditis and preoperative TSH levels were correlated with postoperative
levothyroxine supplementation to maintain euthyroid status, in univariate and multivariate analyses. Conclusion: High preoperative TSH levels and/or
thyroiditis indicate a significantly increased likelihood of developing
hypothyroidism requiring
thyroid hormone supplementation after a thyroid lobectomy. Patients with an increased risk of postoperative
hypothyroidism must be aware of their risk factors and should undergo more intensive follow-ups.