The effect of ligation of the inferior thyroid artery upon thyroid remnant function

The cause of hypothyroidism after subtotal thyroidectomy for primary thyrotoxicosis is not precisely understood. Activity is not just related to the size of the thyroid remnants, and ischemia of the remnants has been suggested as a factor which might contribute to the development of hypothyroidism. A prospective study has been carried out to look for evidence that ischemia is implicated. In 55 patients undergoing subtotal thyroidectomy for primary thyrotoxicosis, the inferior thyroid artery (ITA) was ligated on one side but preserved on the opposite side. All of the patients had postoperative isotope scans. We predicted that, if ITA ligation produced significant ischemia of the remnant, then the remnant with the intact ITA ought to show greater activity on the postoperative scan. This was not the case. The remnant with the intact ITA was dominant in only 15 of 55 patients, the remnant with the ligated ITA was dominant in the same proportion, 15 of 55 patients, while in the remaining 25 patients, activity was equally distributed between the two remnants. The results of this study provides no evidence to support the contention that nonligation of the inferior thyroid arteries will reduce ischemia of the thyroid remnants and thereby discourage postoperative hypothyroidism.