Benign Thyroid Nodule with Normal Iodide Trap and Defective Organification N. DEMEESTER-MIRKINE, J. VAN SANDE, J. CORVILAIN, AND J. E. DUMONT Departments of Radioisotopes and Endocrinology, Brugmann University Hospital, Queen Elisabeth Foundation and Institute of Interdisciplinary Research, School of Medicine and Biology Department, Euratom,* Brussels, Belgium ABSTRACT. Cold thyroid nodules are generally due to impaired iodide uptake, while organification remains normal. In a case of a nodule appearing hot one hour after Tc 99 m and cold 24 h after 131I-iodide, in vivo investigations showed that the trapping function was unimpaired and that the defect lay in organification. An early thyroid scan taken with
131 I-iodide showed definite radioactivity in the nodule which was dischargeable by K perchlorate. This finding was confirmed by in vitro study of the tissue. Indirect evidence suggests that a defect was present in the H2O2 generating system rather than in peroxidase. (/ Clin Endocrinol Metab 41: 1169,1975)
OLD thyroid nodules are, by definition, nodules which, when compared to normal thyroid regions of the same subject, contain little or no radionuclide (usually radioiodine) at the time of thyroid scintigraphy. Failure to accumulate iodide might conceivably be due to impaired iodide trapping or binding to proteins. Until now, only the first mechanism has been demonstrated (1,2). We present a case in which only iodide organification in the nodule was defective. Iodide trapping was intact but the iodide was subsequently released so that the scintigram at 24 hours showed a cold nodule.
Thyroid uptake was measured with a Philips flat-field collimator built according to International Atomic Energy Agency standards; scintigrams were made with a Picker Magnascanner.
C
Materials and Methods The patient was a 30-year-old woman with a single nodule 3 cm in diameter in the right lobe of an otherwise apparently normal thyroid gland. Euthyroidism was established by the classic parameters. Thyroid uptake of 131 I-iodide at 24 h: 48% (normal range: 30-60%); T3 resin uptake: 115% (normal range: 90-120%); T4 iodine: 4.5 fig% (normal range: 3.5-7.0%); free T4 index: 3.9 (normal range: 3.0-7.5). Our attention was attracted by the difference between the scintigrams: the nodule was hot one hour after pertechnetate Tc 99 m and cold 24 hours after 131I-iodide administration. Histologic examination of the nodule removed at surgery showed an homogenous micro vesicular ade-
Received April 11, 1975. Work carried out partially under contract with the Ministere de la Politique Scientifique within the framework of the Association Euratom—University of Brussels—University of Pisa. * Publication number Bio 1258. Reprints: N. Demeester-Mirkine, Departement des Radioisotopes, Service de Medecine, Hopital Brugmann, 4, Place Van Gehuchten, 1020 Bruxelles, Belgium.
Perchlorate test. After intravenous injection of 150 /AC 131 I-iodide, thyroid uptake was measured for 4 min at 60, 90 and 120 min; scintigrams were performed at 45, 95 and 125 min. At the 63rd min after the injection, 400 mg of potassium perchlorate was administered orally (3). The distribution of activity between the normal lobe and the nodule was estimated by dot counting on the scans. Knowing the uptake in the whole gland, we could calculate the uptake in each of the two zones in percentage of the dose of 131I. The percentage fall in 131I uptake in the two zones after KC1O4 administration was calculated as follows: (or 120)
U60 Ufi
- (Fig. 2)
where U60 is the uptake at 60 min. A positive perchlorate discharge value indicates a fall in thyroid radioactivity and a negative one an increase. In vitro studies. The tissue removed at surgery was dissected, sliced and incubated in Krebs Ringer bicarbonate buffer supplemented with glucose 8 mM, albumin 0.5 g/1, iodide 0.04 mM and 131I-iodide 0.5 /ic/ml in an atomosphere of 95% O2, 5% CO2 (4). Some flasks were supplemented with d alanine 50 mM and d aminoacid oxidase (Sigma) 70 mU/ml, or with glucose oxidase 25 mg/1 as H2O2 providing systems. After one h of incubation the slices were removed, blotted on filter paper and homogenized in 2 mM methimazole. The 131I content of the slices and the activity of the trichloracetic insoluble fraction were counted in a Philips well type scintillation counter (4). Cyclic 3'5' AMP was measured in the aqueous extract of boiled slices after Gilman (5). Bovine TSH (Thytropar) was purchased from Armour (Kankakee, U.S.A.).
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JCE & M • 1975 Vol 41 • No 6
COMMENTS
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Results The scintigram taken one h after 1 me of Tc 99 m pertechnetate showed selective uptake by the nodule whereas the image obtained 24 h after 131 I-iodide showed a cold nodule (Fig. 1). The scintigram taken 45 min after the injection of 131 I-iodide also showed selective uptake in the nodule. The administration of KC1O4 63 min after the 131I-iodide injection discharged the activity from the nodule which appeared cold on the images obtained at 95 and 125 min. The evolution of uptake in the nodule (Fig. 2) is comparable to that described in glands affected by impaired organification (3) while the nonnodular tissue responds as a normal gland. Uptake in the whole gland in percentage of the dose was 11.1% at 60 min, 8.4% at 90 min, 8.1% at 120 min; in the normal lobe 2.7%, 4.1% and 4.2%; in the nodule 8.4%, 4.3% and 3.9%. In agreement with the in vivo data, slices from nodular tissue took up much more iodide than slices from normal tissue (393,250 ± 29,476 cpm/ 100 mg wet weight™. 141,000 ± 17,434 cpm/100
'•IV. 1
N0RMAL LOBE
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•50-
60
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90 120 Time after 1131 injection (minutes)
FIG. 2. Per cent fall in thyroid 131I content after KCIO4 administration. There is a positive discharge of activity from the nodule whereas activity remains in the normal lobe. mg wet weight, mean ± SEM). Moreover, in the absence of an H2O2 generating system, slices of the nodular tissue did not bind this iodide to proteins (0.22% ± 0.02% of total iodide taken up; background of the method 0.20 to 0.30%) in contrast to normal tissue (0.85% ± 0.05%). On the other hand, in the presence of H2O2 generating systems, iodination was equal in both types of slices, normal tissue (3.7 ± 1.5% with d amino acid oxidase, 3.7 ± 0.9% with glucose oxidase) and nodular tissue (2.4% ± 0.2% with d amino acid oxidase, 4.1% ± 1.1% with glucose oxidase). TSH (1 mU/ml) increased cyclic 3'5' AMP accumulation in normal (from 59 ± 1 pM/100 mg wet weight to 157 ± 15) and in nodular tissue slices (from 43 ± 3 pW100 mg wet weight to 79 ± 1).
• '
Discussion D FIG. 1. Scintigrams with Tc 99 m and 131I. The scintigrams taken 1 h after Tc 99 m pertechnetate (A) shows selective trapping in the right nodule whereas 24 h after 131I-iodide the nodule is cold (B). An early 131 I-iodide scan, performed 45 min after iv injection shows a hot nodule (C) which becomes cold 62 min after KC1O4 discharge (D).
These data show a cold nodule due to organification impairment rather than to defective trapping. The defect was demonstrated in vivo in the nodule while the rest of the gland reacted normally. The sequence of thyroid scans at 1 h and 24 h showed that 131I-iodide was trapped at an early stage but was subsequently released since the nodule was cold at 24 h. The fact that the
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1171
COMMENTS nodules activity was selectively dischargeable by perchlorate in vivo shows that iodide was retained as such, and thus that organification was impaired. Since Tc 99 m pertechnetate behaves as a tracer of the trap, this nodule appeared hot on the pertechnetate scan. In clinical practice, similar disparities between Tc 99 m and I31I-iodide scintigrams have been reported (6-10). The phenomenon is rare and does not correspond to any particular pathologic lesion (11). Even some cases of thyroid cancer have presented the anomaly (6). Consequently, the use of a Tc 99 m scan may be less valid than l3l I-iodide scan to preclude cold nodules, i.e. nodules suspected of malignancy. The cause of the biochemical disturbance is still a matter of speculation. Anatomic investigations of tissues presenting the anomaly have shown no particular structure suggesting a subcellular defect (11). In this case, the fact that no iodination was obtained in nodular tissue in the absence of exogenous H2O2 and that with H2O2 this tissue binds iodide as effectively as normal tissue suggests that the defect resides not in the use of H2O2 by thyroid peroxidase but in the H2O2 generating system (12,13). Most organification defects which have been studied have been congenital and have affected the whole gland; such defects have also been described in a few cases of thyroid cancer (6,14,15). In the present case the defect was acquired and localized. The homogeneity of the function of the nodule suggests a single mutation and argues in favor of the nodule's probable unicellular origin. The reason for more intensive early trapping in the nodular tissue compared to the normal lobe
also remains to be elucidated. However this finding is in keeping with the concept that iodide trapping is regulated by iodide supply by way of an intrathyroidal feedback loop (16).
Acknowledgments We thank R. Heimann, M.D. for reviewing the pathology and Mrs. N. Dubois for skillful technical help.
References 1. Field, J. B., P. R. Larsen, K. Yamashita, K. Mashiter, and A. DekkerJ Clin Invest 52: 2404, 1973. 2. De Groot, L. J., Ada Endocrinol Panam 1: 27, 1970. 3. Stewart, R. D. H., and I. P. C. Murray, J Clin Endocrinol Metab 26: 1050, 1966. 4. Rodesch, F., P. Neve, C. Willems, and J. E. Dumont, EurJ Biochem 8: 26, 1969. 5. Gilman, A. G., Proc Nat Acad Sci (US) 67: 305, 1970. 6. Steinberg, M., R. R. Cavalieri, and S. H. Choy J Clin Endocrinol Metab 31: 81, 1970. 7. Atkins, H. L., J. F. Klopper, R. M. Lambrecht, and A. P. Wolf, Am] Roentgenol Radium Ther Nucl Med 117: 195, 1973. 8. Massin, J. P., J. Karam, and J. C. Savoie, Ann Endocrinol (Paris) 31: 962, 1970. 9. Strauss, H. W., P. J. Hurley, and H. N. Wagner, Radiology 97: 307, 1970. 10. Usher, M. S., and A. Y. Arzoumanian J Nucl Med 12: 136, 1971. 11. Shambaugh, G. E. Ill, J. L. Quinn, R. Oyasu, and N. Freinkel, JAMA 228: 866, 1974. 12. Dumont, J. E., Vitam Horrn 29: 287, 1971. 13. De Groot, L. J., N Engl J Med 272: 243, 1965. 14. Wolff, J., J. Robbins, and J. E. Rail, Endocrinology 64: 1, 1959. 15. Valenta.L.J Clin Endocrinol Metab 26: 1317,1966. 16. Ingbar, S. H., Mayo Clin Proc 47: 814, 1972.
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131 I-iodide showed definite radioactivity in the nodule which was dischargeable by K perchlorate. This finding was confirmed by in vitro study of the tissue. Indirect evidence suggests that a defect was present in the H2O2 generating system rather than in peroxidase. (/ Clin Endocrinol Metab 41: 1169,1975)
OLD thyroid nodules are, by definition, nodules which, when compared to normal thyroid regions of the same subject, contain little or no radionuclide (usually radioiodine) at the time of thyroid scintigraphy. Failure to accumulate iodide might conceivably be due to impaired iodide trapping or binding to proteins. Until now, only the first mechanism has been demonstrated (1,2). We present a case in which only iodide organification in the nodule was defective. Iodide trapping was intact but the iodide was subsequently released so that the scintigram at 24 hours showed a cold nodule.
Thyroid uptake was measured with a Philips flat-field collimator built according to International Atomic Energy Agency standards; scintigrams were made with a Picker Magnascanner.
C
Materials and Methods The patient was a 30-year-old woman with a single nodule 3 cm in diameter in the right lobe of an otherwise apparently normal thyroid gland. Euthyroidism was established by the classic parameters. Thyroid uptake of 131 I-iodide at 24 h: 48% (normal range: 30-60%); T3 resin uptake: 115% (normal range: 90-120%); T4 iodine: 4.5 fig% (normal range: 3.5-7.0%); free T4 index: 3.9 (normal range: 3.0-7.5). Our attention was attracted by the difference between the scintigrams: the nodule was hot one hour after pertechnetate Tc 99 m and cold 24 hours after 131I-iodide administration. Histologic examination of the nodule removed at surgery showed an homogenous micro vesicular ade-
Received April 11, 1975. Work carried out partially under contract with the Ministere de la Politique Scientifique within the framework of the Association Euratom—University of Brussels—University of Pisa. * Publication number Bio 1258. Reprints: N. Demeester-Mirkine, Departement des Radioisotopes, Service de Medecine, Hopital Brugmann, 4, Place Van Gehuchten, 1020 Bruxelles, Belgium.
Perchlorate test. After intravenous injection of 150 /AC 131 I-iodide, thyroid uptake was measured for 4 min at 60, 90 and 120 min; scintigrams were performed at 45, 95 and 125 min. At the 63rd min after the injection, 400 mg of potassium perchlorate was administered orally (3). The distribution of activity between the normal lobe and the nodule was estimated by dot counting on the scans. Knowing the uptake in the whole gland, we could calculate the uptake in each of the two zones in percentage of the dose of 131I. The percentage fall in 131I uptake in the two zones after KC1O4 administration was calculated as follows: (or 120)
U60 Ufi
- (Fig. 2)
where U60 is the uptake at 60 min. A positive perchlorate discharge value indicates a fall in thyroid radioactivity and a negative one an increase. In vitro studies. The tissue removed at surgery was dissected, sliced and incubated in Krebs Ringer bicarbonate buffer supplemented with glucose 8 mM, albumin 0.5 g/1, iodide 0.04 mM and 131I-iodide 0.5 /ic/ml in an atomosphere of 95% O2, 5% CO2 (4). Some flasks were supplemented with d alanine 50 mM and d aminoacid oxidase (Sigma) 70 mU/ml, or with glucose oxidase 25 mg/1 as H2O2 providing systems. After one h of incubation the slices were removed, blotted on filter paper and homogenized in 2 mM methimazole. The 131I content of the slices and the activity of the trichloracetic insoluble fraction were counted in a Philips well type scintillation counter (4). Cyclic 3'5' AMP was measured in the aqueous extract of boiled slices after Gilman (5). Bovine TSH (Thytropar) was purchased from Armour (Kankakee, U.S.A.).
1169
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JCE & M • 1975 Vol 41 • No 6
COMMENTS
1170
Results The scintigram taken one h after 1 me of Tc 99 m pertechnetate showed selective uptake by the nodule whereas the image obtained 24 h after 131 I-iodide showed a cold nodule (Fig. 1). The scintigram taken 45 min after the injection of 131 I-iodide also showed selective uptake in the nodule. The administration of KC1O4 63 min after the 131I-iodide injection discharged the activity from the nodule which appeared cold on the images obtained at 95 and 125 min. The evolution of uptake in the nodule (Fig. 2) is comparable to that described in glands affected by impaired organification (3) while the nonnodular tissue responds as a normal gland. Uptake in the whole gland in percentage of the dose was 11.1% at 60 min, 8.4% at 90 min, 8.1% at 120 min; in the normal lobe 2.7%, 4.1% and 4.2%; in the nodule 8.4%, 4.3% and 3.9%. In agreement with the in vivo data, slices from nodular tissue took up much more iodide than slices from normal tissue (393,250 ± 29,476 cpm/ 100 mg wet weight™. 141,000 ± 17,434 cpm/100
'•IV. 1
N0RMAL LOBE
-50-
.£
•50-
60
NODULE
90 120 Time after 1131 injection (minutes)
FIG. 2. Per cent fall in thyroid 131I content after KCIO4 administration. There is a positive discharge of activity from the nodule whereas activity remains in the normal lobe. mg wet weight, mean ± SEM). Moreover, in the absence of an H2O2 generating system, slices of the nodular tissue did not bind this iodide to proteins (0.22% ± 0.02% of total iodide taken up; background of the method 0.20 to 0.30%) in contrast to normal tissue (0.85% ± 0.05%). On the other hand, in the presence of H2O2 generating systems, iodination was equal in both types of slices, normal tissue (3.7 ± 1.5% with d amino acid oxidase, 3.7 ± 0.9% with glucose oxidase) and nodular tissue (2.4% ± 0.2% with d amino acid oxidase, 4.1% ± 1.1% with glucose oxidase). TSH (1 mU/ml) increased cyclic 3'5' AMP accumulation in normal (from 59 ± 1 pM/100 mg wet weight to 157 ± 15) and in nodular tissue slices (from 43 ± 3 pW100 mg wet weight to 79 ± 1).
• '
Discussion D FIG. 1. Scintigrams with Tc 99 m and 131I. The scintigrams taken 1 h after Tc 99 m pertechnetate (A) shows selective trapping in the right nodule whereas 24 h after 131I-iodide the nodule is cold (B). An early 131 I-iodide scan, performed 45 min after iv injection shows a hot nodule (C) which becomes cold 62 min after KC1O4 discharge (D).
These data show a cold nodule due to organification impairment rather than to defective trapping. The defect was demonstrated in vivo in the nodule while the rest of the gland reacted normally. The sequence of thyroid scans at 1 h and 24 h showed that 131I-iodide was trapped at an early stage but was subsequently released since the nodule was cold at 24 h. The fact that the
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1171
COMMENTS nodules activity was selectively dischargeable by perchlorate in vivo shows that iodide was retained as such, and thus that organification was impaired. Since Tc 99 m pertechnetate behaves as a tracer of the trap, this nodule appeared hot on the pertechnetate scan. In clinical practice, similar disparities between Tc 99 m and I31I-iodide scintigrams have been reported (6-10). The phenomenon is rare and does not correspond to any particular pathologic lesion (11). Even some cases of thyroid cancer have presented the anomaly (6). Consequently, the use of a Tc 99 m scan may be less valid than l3l I-iodide scan to preclude cold nodules, i.e. nodules suspected of malignancy. The cause of the biochemical disturbance is still a matter of speculation. Anatomic investigations of tissues presenting the anomaly have shown no particular structure suggesting a subcellular defect (11). In this case, the fact that no iodination was obtained in nodular tissue in the absence of exogenous H2O2 and that with H2O2 this tissue binds iodide as effectively as normal tissue suggests that the defect resides not in the use of H2O2 by thyroid peroxidase but in the H2O2 generating system (12,13). Most organification defects which have been studied have been congenital and have affected the whole gland; such defects have also been described in a few cases of thyroid cancer (6,14,15). In the present case the defect was acquired and localized. The homogeneity of the function of the nodule suggests a single mutation and argues in favor of the nodule's probable unicellular origin. The reason for more intensive early trapping in the nodular tissue compared to the normal lobe
also remains to be elucidated. However this finding is in keeping with the concept that iodide trapping is regulated by iodide supply by way of an intrathyroidal feedback loop (16).
Acknowledgments We thank R. Heimann, M.D. for reviewing the pathology and Mrs. N. Dubois for skillful technical help.
References 1. Field, J. B., P. R. Larsen, K. Yamashita, K. Mashiter, and A. DekkerJ Clin Invest 52: 2404, 1973. 2. De Groot, L. J., Ada Endocrinol Panam 1: 27, 1970. 3. Stewart, R. D. H., and I. P. C. Murray, J Clin Endocrinol Metab 26: 1050, 1966. 4. Rodesch, F., P. Neve, C. Willems, and J. E. Dumont, EurJ Biochem 8: 26, 1969. 5. Gilman, A. G., Proc Nat Acad Sci (US) 67: 305, 1970. 6. Steinberg, M., R. R. Cavalieri, and S. H. Choy J Clin Endocrinol Metab 31: 81, 1970. 7. Atkins, H. L., J. F. Klopper, R. M. Lambrecht, and A. P. Wolf, Am] Roentgenol Radium Ther Nucl Med 117: 195, 1973. 8. Massin, J. P., J. Karam, and J. C. Savoie, Ann Endocrinol (Paris) 31: 962, 1970. 9. Strauss, H. W., P. J. Hurley, and H. N. Wagner, Radiology 97: 307, 1970. 10. Usher, M. S., and A. Y. Arzoumanian J Nucl Med 12: 136, 1971. 11. Shambaugh, G. E. Ill, J. L. Quinn, R. Oyasu, and N. Freinkel, JAMA 228: 866, 1974. 12. Dumont, J. E., Vitam Horrn 29: 287, 1971. 13. De Groot, L. J., N Engl J Med 272: 243, 1965. 14. Wolff, J., J. Robbins, and J. E. Rail, Endocrinology 64: 1, 1959. 15. Valenta.L.J Clin Endocrinol Metab 26: 1317,1966. 16. Ingbar, S. H., Mayo Clin Proc 47: 814, 1972.
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