Hyperfunctioning thyroid nodules are common, yet there is controversy about their management [1, 2, 21]. The different modalities used include surgery, radioiodine, and percutaneous ethanol injection [1, 22]. The studies carried out over the past decade on the efficacy of PEI in the treatment of autonomous thyroid nodules indicate that it is effective, requires no anaesthesia, and carries minimal risk [19, 23]. In our study, PEI also proved to be an effective treatment for patients with hyperfunctioning thyroid nodules and either clinical or sub-clinical hyperthyroidism. None of our patients reported symptoms of hyperthyroidism after PEI and all of them achieved normal peripheral thyroid hormone levels. At 3 months follow-up, only 3 patients showed persistent sTSH suppression in spite of normal thyroid hormone levels. Reduction in the volume of nodules was significant at 3 months [P < 0.001], with an average value of l2.48 ± 10.6 ml per nodule. The success rate for this study (91.3%) is consistent with that reported elsewhere (54–100%) [18, 19, 23, 25]. Two large studies from Italy, one on 132 patients followed up over 8.5 years  and the other on 117 patients followed up over 5 years , suggest that PEI be recommended as treatment for hyperfunctioning thyroid adenoma with sub-clinical hyperthyroidism. The success rate in our patients is higher, however, than that reported in a number of larger series, notably that reported by Lippi et al , in which the overall success rate was 45.9% at 3 months, increasing to 73.9% at one year. 99 Tm scans were only performed before treatment in our patients; follow-up scanning may well have reduced our success rate too.
PEI can also be recommended as alternative therapy in patients at high-risk for surgery (even when the nodules are large) or for patients in whom radioactive iodine may have relative contraindication(s) [2, 18, 25, 27]. Many authors further stress that PEI should only be carried out in centres thoroughly familiar with the technique required [28–31]. Transient dysphonia (spontaneous recovery over a period of weeks or months) has been reported in 2–5% of cases [20, 30, 32]. The pathology in every case has been either direct chemical injury to the recurrent laryngeal nerves, secondary to alcohol leakage outside the nodule, or nerve injury due to a sudden elevation in pressure inside the nodule. Two cases of transient vocal cord paralysis were seen in our patients; one recovered fully after 1 week, the other fully after 6 months. Real-time ultrasound used to monitor the PEI procedure can identify ethanol leakage, which shows up as a hyperechogenic area, as it is happening. One group has suggested that, in order to minimise the risk involved, a bolus of 2% Xylocaine (0.2–0.5 ml) should be injected first in order to mark the injection path before PEI itself is begun . We omitted this approach because the nodules were all clearly identifiable by ultrasound and there was little risk of leakage. Studies have shown that ethanol produces coagulative necrosis of nodular tissue through hemorrhagic infarction and vascular thrombosis [33, 34]. Furthermore, in the area of viable tissue surrounding the zone of biochemical ablation, enzyme activity is reduced. The areas of necrotic thyroid parenchyma are clearly distinguishable from the seemingly normal thyroid tissue surrounding them, which is free of any evidence of inflammation [33, 34]. The probability of recurrence is virtually eliminated once granulation scar tissue replaces the nodule. Hypothyroidism is not observed even after prolonged follow-up [26, 35]. Recurrence of hyperthyroidism has not been reported in patients who have had a complete response to PEI [26, 35]. Our study confirms this. It should be noted that a number of our patients had multinodular goitre, with more than one hot nodule being detected on radioisotope scanning. In experienced hands, major complications of PEI, such as fibrosis of adjacent tissues or thrombogenesis within the large vessels of the neck, are unlikely . T3 and T4 levels in both pre-toxic and toxic patients decreased significantly [P < 0.001], and sTSH levels increased significantly, in response to PEI [P < 0.01]. The most important factors in predicting response to PEI are initial nodule volume and the level of skill possessed by the physician performing the procedure. Significant nodule shrinkage following PEI has already been reported in the literature . Our findings confirm this. There exists a direct linear relationship between reduction in nodule volume and initial nodule volume (r = 0.94, p = 0.007), that is to say the greater the initial size of the nodule, the larger the reduction in size.
PEI is also effective in non-toxic thyroid nodules in young patients [6, 36]. However, since the conversion rate for non-toxic nodules (to toxic nodules) is 1.2–5.7 percent/year depending on the follow-up series [37, 38], many authors recommend conservative therapy for patients with non-toxic hot nodules. Furthermore, given that long-term sub-clinical hyperthyroidism is associated with increased bone turnover and accelerated bone demineralisation, and that in patients with concomitant heart disease, the increased quantity of hormone secreted by an autonomous nodule may produce arrhythmias or lead to cardiac failure, treatment of hyperfunctioning nodules with suppressed sTSH becomes necessary and PEI may be a reasonable alternative in some cases [1, 2, 14, 36, 39].