J. Endocrinol. Invest. 19: 71-75,1996 Improvement of upper airway obstruction after 131 I-treatment of multinodular nontoxic goiter evaluated by flow volume loop curves B. Nygaard*, U. S0es-Petersen*, P.F. H0ilund-Carlsen**, A. Veje**, P.E. Holst*, A. Vestergaard***, and K. S01ling* *Department of Internal Medicine, **Department of Nuclear Medicine and ***Department of Radiology, Holbcek Hospital, Denmark ABSTRACT. Symptoms of tracheal-esophageal compression are often related to a large nontoxic goiter. The aim of the present study was to eval- uate to what degree upper airway obstruction, as measured by flow volume loops, FIFso% and FEFsooJFIFso% (Forced Expiratory Flow at 50% of the vital capacity/ Forced Inspiratory Flow at 50% of the vital capacity) exists in nontoxic multinodular goiter, and whether changes occur after 131l-treat- ment. Thirteen patients with large multinodular non- toxic goiters were evaluated by estimation of FIF SO %' FEFsooJFIF so % ratio and a graphic plot of the flow volume loop curve before and three, six and 12 months after treatment with 1311. FIFso% increased over 12 months from median 1.79 I/sec (range 1.46- INTRODUCTION 131 I-treatment is an attractive alternative to surgery in the treatment of multinodular nontoxic goiter. We and others (1-6) have found a reduction in goiter size after treatment with 131 1, to approximately 45% after two years. Reduction of thyroid volume is seen already one month after treatment (5, 7), there is no recurrence of goiter, and apart from hypothy- roidism in 20% of the cases after four years, there are very few side effects (5). It is well known that goiter may cause tracheal com- pression but the prevalence is not well-known. Symptoms of tracheal-esophageal compression are often the indication of treatment both by surgery (8, 9) and 131 1 (5, 7). The best parameter related to upper airway ob- struction seems to be an evaluation of the flow vol- ume loop curve, a graphical display of airflow as a Key-words: Flow volume loop, radioiodine, goiter. Correspondence: Birte Nygaard, MD. Hedebyvej 3, OK - 3650 0lstykke, Denmark. Accepted August 29, 1995. 71 3.02) to 2.84 I/sec (1.13-5.69) (p:=O.01). A progres- sive increase was seen over time (p:=O.001, trend analysis). The FEF 50 oJFIF 50 % ratio decreased from in 1.45 (0.32-2.26) to 1.03 (0.43-2.13) 12 months after treatment (p<O.001). A progressive decrease was seen over time (p:=O.001, trend analysis). By visual evaluation 11 had a flow volume loop curve typical for an upper airway obstruction and in 9 pa- tients the FEF 50 oJFIF so % ratio was >1.2. In conclu- sion we found that upper airway obstruction is pre- sent in patients with multinodular nontoxic gOiter, and seems to be reduced after 131 I-treatment. Flow volume loop curves and measurement of FEF 50 % and FIFso% are important estimates for upper air- way obstruction in these patients. function of the pulmonary volume (10). At maximal effort the shape of the curve is determined by air- way diameter and elastic forces in the lung. An ob- struction of the upper airways - as for instance tra- cheal compression from a large goiter - will change the shape of the curve in a characteristic way by reducing and limiting the inspiratory airflow. Also patients with upper airway obstruction is charac- terized by a FEF50o;)FIF50% (Forced Expiratory Flow at 50% of the vital capacity/ Forced Inspiratory Flow at 50% of the vital capacity) ratio> 1.2 (10). In patients with tracheal compression from goiter, it has been shown by means of flow volume loop curves, that the upper airway obstruction was re- lieved after thyroidectomy (9, 11). The aim of the present study was to evaluate to what degree upper airway obstruction, as measured by flow volume loops, exists in nontoxic multinodular goi- ter, and whether changes occur after 131 I-treatment. MATERIALS AND METHODS Patients Thirteen consecutive patients (two men and 11 women, median age 55 years, range 45-81 years)