S. Ertek, R.Ü. Ersoy, C. AnIl, Ö. Demir, M.F. Erdog˘an, S. Güllü, D. Berker, K. Gül, U. Ünlütürk, G. Erdog˘an; Ankara Thyroid Study Group gives clues prior to surgical intervention about pathol- ogy of the nodule [3], and improved ultrasonographic techniques provide better evaluation of the whole thyroid parenchyma. Therefore, surgical interventions aimed at saving the nodule-free part of the thyroid parenchyma are increasingly employed, to avoid postoperative hypothyroidism and complications of bilateral surgical techniques [4, 5]. Thyroid lobectomy or hemithyroidectomy has advantages over total thyroidectomy [4-6] for soli- tary nodules but it comes with the risk of nodule recurrence [4-6]. Nodule recurrence may be prob- lematic during follow-up, particularly in patients who are found to have carcinoma at postopera- tive pathological evaluation [4-6]. Higher risk of nodule recurrence or risk of hypothyroidism after hemithyroidectomy, increase in remaining thyroid lobe volume and/or nodule volume and benefits of levothyroxine (LT4) use in these patients remain unclear [6-11]. Meanwhile, the role of iodine defi- ciency or the effects of successful iodization (as in Turkey) on nodule recurrence after hemithy- roidectomy still remain unknown [12, 13]. Iodine intake may have effects in Hashimoto thyroiditis (HT) [14]. It is also not clear whether presence of HT may have an impact on nodular recurrence in these patients. In the present study we sought the risk factors that may be associated with nodular recurrence, hypothyroidism, increase in thyroid lobe or nodule volume in patients with or without HT, and in patients on and not on LT4 use, by evaluation of longitudinal data of patients who had undergone hemithyroidectomy. Material and methods We enrolled 140 patients (27 men, 113 women) within ages 18-80 years from five different hos- pitals in Ankara. We included patients who had undergone hemithyroidectomy and had records of two different visits which were separated by at least 6 months duration. Patients with a his- tory of multiple thyroid operations, radioactive iodine treatment, patients who were receiving drugs for other ailments that may affect thyroid functions (such as amiodarone or steroids), hypophyseal pathologies, patients with renal impairments and patients who had changes in the drug regimen between the 2 visits were excluded. Second visit measurements were accepted if they were a minimum of 3 months after the surgery, to exclude effects of postoper- ative oedema and thyroid function variations. The interval between the two visits was 30.6 ±9.7 months. All patients were informed about the study and all provided written informed consent before their evaluation. The study was approved by the Ethical Committee of Ufuk University as the main centre and carried out following the principles of the Helsinki Conference. We collected data on the pre- and postoperative diagnosis at the first visit, on thyroid function tests (TSH, free T4 and free T3), serum thyroid autoanti- bodies, LT4 use, remaining lobe volume, and nod- ule volumes on ultrasonography at both visits, and assessed for the presence and/or appearance of new nodules on the second visit. Nodules were defined as > 3 mm diameter on ultrasonography in all three dimensions and ultrasonographic thyroid evaluation was made by the same endocrinologists educated by the same thyroid centre. Increase in nodule volume was defined as > 20% increase in at least two dimensions of the nodule and increase in lobe volume was defined as > 10% increase in lobe volume across the study interval [15, 16]. Hypothyroidism was defined as serum TSH ≥ 5 mIU/ ml, including subclinical hypothyroidism. For diagnosis of HT, we accepted pathological examination of operated thyroid lobe parenchyma. Hormonal measurements and thyroid autoantibodies Thyroid function tests (TSH, free T4, free T3) were measured by electrochemiluminescence immunoas- say (ECLIA) Immulite 2000 (Diagnostic Products Corp, Los Angeles, CA, USA) and Abbot Architect 2000 in four hospitals and by the same method, and by Elecsys 170® in one hospital. Measured TSH levels were recorded as mIU/ml and free T4 and free T3 as pmol/l to have the same SI (Syste`me International d'Unités) units. Thyroid autoantibod- ies were measured by the competitive radioim- munoassay (RIA) method (using Brahms® Dynotest) in one hospital, by the ECLIA method using Roche Elecsys 2010 in another hospital, and by the ECLIA method using Abbott Architect 2000 in three oth- er hospitals. Interchangeability of Roche Elecsys 2010 and Abbot Architect 2000 measurements was tested before starting the study. Ultrasonographic evaluation Three university hospitals used General Electric® Logiq 5000 and a 9 mHz linear probe, and two hos- pitals used Esaote Colour Doppler US (MAG Tech- nology Co, Ltd. Model: 796FDII Yung-ho City, Taipei; Taiwan) ultrasonography and a 9 mHz linear probe and General Electric Logiq 400 and an 11 mHz lin- ear probe. Three dimensions of the thyroid gland were recorded and thyroid and nodule volumes were calculated by the formula “length X height X depth X pi/6” as ml [17]. Ultrasonographic evalua- tions were performed by endocrinologists who had ultrasonography education from the same centre (Ankara University, Endocrinology and Metabolic Diseases Department). 264 Arch Med Sci 2, April / 2012