Effect of Lugol's iodine on the vascularity of thyroid gland in hyperthyroidism

Vascularity of the thyroid gland was measured in twenty thyrotoxic patients (including Graves and multinodular goitres) and eight normal subjects by a new objective parameter--'Thyroid Vascularity Index' (TVI). The TVI was calculated by comparing the areas under the normalized thyroid and carotid artery curves up to the time of peak of the arterial curve caused by the first passage of a radioactive bolus. Compared to normal thyroid, all the toxic goitres had increased TVI (p less than 0.001); it being maximum in Graves disease (p less than 0.05). TVI in Graves disease was not affected by carbimazole therapy but decreased dramatically in eight out of ten patients (p less than 0.01) two weeks after Lugol's iodine was added. There was a sustained fall in TVI in all the ten patients (p less than 0.001) with chronic iodine therapy up to six weeks without any hormonal escape. TVI in multinodular goitres showed no significance change with carbimazole or iodine therapy.