Risk factors of hypothyroidism after hemithyroidectomy

Hemithyroidectomy has been increasingly applied in patients with thyroid diseases. Although patients are expected to maintain normal thyroid function after hemithyroidectomy, some patients may develop hypothyroidism, which requires thyroid-hormone substitution. Our aim was to identify the risk factors of postoperative hypothyroidism after hemithyroidectomy.

We conducted a retrospective, analytical and descriptive study including all patients who underwent hemithyroidectomy between 2017 and 2022, with a minimum follow up of 12 months. Hypothyroidism was defined as a postoperative serum thyroid-stimulating hormone (TSH) level higher than 5 mIU/L. Collected and analyzed data included age, sex, personal history of hyperthyroidism, family history of thyroid pathology, preoperative and postoperative TSH, nodule size, side and volume of resected and remaining lobesand definitive histological diagnosis.

A total of 190 patients were included. Mean age of patients was 45.95 years [13;79]. The sex ratio (M/F) was 0.091. Of the 190 patients studied, 30 (15.79%) developed hypothyroidism after surgery. Among these patients 2 cases showed signs of clinical hypothyroidism such as constipation and asthenia. The mean duration of diagnosis after surgery was 3.75 months [1;12]. The personal history of hyperthyroidism, preoperative TSH greater than 1.9, remaining lobe volume less than 3.8 cm3 and the presence of lymphocytic thyroiditis on definitive pathological examination were associated with a significantly increased risk of hypothyroidism after Hemithyroidectomy (p< 0.01).

Preoperative TSH level greater than 1.9, remaining lobe volume less than 3.8 cm3 and the presence of lymphocytic thyroiditis on pathological examination justify postoperative TSH monitoring up to 12 months after surgery.