The compensatory enlargement of the remaining thyroid lobe following hemithyroidectomy is small and without impact on symptom relief.

According to previous studies, hemithyroidectomy results in growth of the remaining thyroid lobe by up to 30% in first 12 months after surgery. However, this estimate is based on imprecise methods, high inter- and intra-observer variability, and lack of blinding of the measurements. Furthermore, it is unknown whether enlargement of the remaining hemi-thyroid interferes with the improvement in symptoms after surgery for goiter. We aimed to assess the impact of postoperative thyroid growth on goiter symptom relief following hemithyroidectomy in patients with benign nodular goiter. Outcomes were measured before and 6 months after hemithyroidectomy in 44 patients. Thyroid volumes were determined by two independent and blinded observers using magnetic resonance imaging (MRI). Inter- and intra-observer variability was visualized by Bland-Altman plots. Goiter symptoms were assessed by the Thyroid-Specific Patient-Reported-Outcome Questionnaire (ThyPRO) on a scale from 0 to 100 points. After hemithyroidectomy, the remaining thyroid lobe was 13.7 ± 6.4 mL, and enlarged by a mean of 1.8 mL over 6 months [95% confidence interval (CI) (1.6; 2.1), p < 0.001], corresponding to an increase of 17% [95% CI (12; 22)]. The Goiter Symptom score improved by 27 points [95% CI (21; 34), p < 0.0001] from median 39 points (range 2-86) at baseline, and was unaffected by the compensatory thyroid growth. Six months after hemithyroidectomy, using blinded MRI evaluations, we demonstrated a small but significant postoperative growth of the remaining hemi-thyroid, which did not significantly affect the considerable improvement in goiter symptoms.