Post-hemithyroidectomy hypothyroidism in non autoimmune thyroiditis patients: Incidence, risk factors and duration of follow up

Abstract

Hemithyroidectomy has a known but less predictable sequelae of hypothyroidism. Presence of anti-thyroid antibody is known, well studied risk factor. Other postulated risk factors include higher pre-operative TSH level and lower ratio of post-operative thyroid remnant to the patient's weight. We reviewed our data to address the above mentioned risk factors. This was a retrospective study done in National Cheng Kung University Hospital, Taiwan from 2015 to 2017. 125 patients underwent hemithyroidectomy, but 24 patients were excluded due to autoimmune thyroiditis, which was determined as the exclusion criteria. Standard panel of blood investigations were taken in each clinic visit before and after operation. A neck ultrasound was done 2 months post-operatively to assess the thyroid remnant. Chi-square test was used for categorical data analysis. Independent student t-test was used for continuous data with parametric distribution and Mann-Whitney U test for non parametric data. p<0.05 was taken as statistically significant. The mean duration of follow up was 29.3 months. 4 out of 101 patients had clinical hypothyroidism; 23 patients developed subclinical hypothyroidism post-hemithyroidectomy. 6 patients of subclinical hypothyroidism had spontaneously recovered within 1 year. Pre-operative TSH >2.0 uIU/mL was a risk factor as Chi square test showed p<0.001. However, thyroid remnants were found not to be a risk factor with the Mann-Whitney U test of p=0.928. Minimum 1 year of follow up for hemithyroidectomy patients was suggested in order not to miss patients developing hypothyroidism post-operatively.