Post-lobectomy Hypothyroidism: Incidence and Risk Factors

Abstract

Background: Risk factors for developing hypothyroidism after hemithyroidectomy have not been sufficiently studied and the incidence of this complication has probably been underestimated. One factor that has been associated is the autoimmune thyroiditis but hypothyroidism is a normal occurrence in the natural course of this disease and is independent of the surgical approach. Methods: Study cohort of patients subjected to thyroid lobectomy secondary to benign (non autoimmune) thyroid disease with a minimal 4-year postsurgical follow-up. Independent variables studied were age, gender, nutritional status as expressed by body mass index (BMI), and TSH levels, and the dependent variable was development or not of hypothyroidism. Incidence and relative risk for each variable were studied. Results: We included 179 patients, 164 women with a mean age of 41.9 years and 15 men with a mean age of 40.6 years. Pathological substrates were nodular colloid goiter in 115 cases, follicular adenoma in 33 cases, adenomatous colloid goiter in 26 cases, and simple cyst in 5 cases. Sixty-seven (37.4%) patients developed hypothyroidism, 45 (67.2%) of these cases within the first 6 weeks of surgery and 22 (32.8%) cases at 6-month follow-up. No further cases of hypothyroidism were identified after 6 months and up to a mean follow- up of 4 years. The only risk factor associated was a preoperative BMI over 25. Conclusion: For patients undergoing lobectomy for a benign non-autoimmune thyroid disease and a BMI over 25, there is a 1.8-fold higher risk of developing hypothyroidism. The incidence of hypothyroidism in patients undergoing hemithyroidectomy is 37.4% and occurs in the first 6 months after surgery.