Georgios K Markantes1, Marina A Michalaki1, George A Vagenakis2, Fotini N Lamari3, Efthymia Pitsi3, Maria Eliopoulou4, Nicholas G Beratis5, Kostas B Markou1. 1. Division of Endocrinology - Department of Internal Medicine, University of Patras Medical School, Patras, Greece. 2. Department of Pediatric Cardiology and Adult Congenital Heart Disease, Onassis Cardiac Surgery Center, Athens, Greece. 3. Laboratory of Pharmacognosy and Chemistry of Natural Products, Department of Pharmacy, University of Patras, Patras, Greece. 4. Endocrinology Unit, Karamandanio Hospital, Patras, Greece. 5. Department of Pediatrics, University of Patras Medical School, Patras, Greece.
Abstract
BACKGROUND: Amiodarone-induced thyrotoxicosis (AIT) is a common and deleterious side effect of amiodarone use. There are two types of AIT, characterized by distinct pathogenic mechanisms and, hence, different treatments. Discriminating between type 1 (AIT1) and type 2 (AIT2) AIT is often very challenging. Beta-glucuronidase (β-G) is a lysosomal enzyme released into the extracellular fluid during inflammation. OBJECTIVES: To examine whether the determination of the plasma activity of β-G is useful in distinguishing AIT1 from AIT2. METHODS: The study included 67 subjects: 9 with AIT1, 9 with AIT2, 14 with hyperthyroidism due to Grave's disease or toxic multinodular goiter, 14 with subacute thyroiditis, and 21 euthyroid controls. Thyroid function tests and plasma β-G activity were determined in all participants, while thyrotoxic patients also underwent thyroid ultrasound/scintigraphy and urine iodine excretion assessment. RESULTS: Plasma β-G activity (expressed as mean ± SD in nmol 4-methylumbelliferone [4-MU]/mL plasma/h) in AIT2 was higher compared to AIT1 (2,263.6 ± 771 vs. 1,101.8 ± 201.9, p < 0.05) and similar to subacute thyroiditis (2,263.6 ± 771 vs. 2,083.2 ± 987.5, p = ns). β-G activity did not differ significantly between AIT1 and controls (1,101.8 ± 201.9 vs. 954.6 ± 248.6, p = ns). ROC curve analysis revealed that β-G activity had a high predictive value for destructive processes, namely AIT2 and subacute thyroiditis (AUC 0.846, 95% CI 0.748-0.943) and a cut-off value of 1,480.5 nmol 4-MU/mL plasma/h was able to discriminate between destructive and non-destructive thyroid conditions with 74% sensitivity and 82% specificity. CONCLUSION: In our study, plasma β-G activity performed well in distinguishing AIT1 from AIT2. Further studies are warranted to establish its usefulness as a discriminator between the two AIT types.
BACKGROUND: Amiodarone-induced thyrotoxicosis (AIT) is a common and deleterious side effect of amiodarone use. There are two types of AIT, characterized by distinct pathogenic mechanisms and, hence, different treatments. Discriminating between type 1 (AIT1) and type 2 (AIT2) AIT is often very challenging. Beta-glucuronidase (β-G) is a lysosomal enzyme released into the extracellular fluid during inflammation. OBJECTIVES: To examine whether the determination of the plasma activity of β-G is useful in distinguishing AIT1 from AIT2. METHODS: The study included 67 subjects: 9 with AIT1, 9 with AIT2, 14 with hyperthyroidism due to Grave's disease or toxic multinodular goiter, 14 with subacute thyroiditis, and 21 euthyroid controls. Thyroid function tests and plasma β-G activity were determined in all participants, while thyrotoxic patients also underwent thyroid ultrasound/scintigraphy and urine iodine excretion assessment. RESULTS: Plasma β-G activity (expressed as mean ± SD in nmol 4-methylumbelliferone [4-MU]/mL plasma/h) in AIT2 was higher compared to AIT1 (2,263.6 ± 771 vs. 1,101.8 ± 201.9, p < 0.05) and similar to subacute thyroiditis (2,263.6 ± 771 vs. 2,083.2 ± 987.5, p = ns). β-G activity did not differ significantly between AIT1 and controls (1,101.8 ± 201.9 vs. 954.6 ± 248.6, p = ns). ROC curve analysis revealed that β-G activity had a high predictive value for destructive processes, namely AIT2 and subacute thyroiditis (AUC 0.846, 95% CI 0.748-0.943) and a cut-off value of 1,480.5 nmol 4-MU/mL plasma/h was able to discriminate between destructive and non-destructive thyroid conditions with 74% sensitivity and 82% specificity. CONCLUSION: In our study, plasma β-G activity performed well in distinguishing AIT1 from AIT2. Further studies are warranted to establish its usefulness as a discriminator between the two AIT types.
Authors: L Tomisti; C Urbani; G Rossi; F Latrofa; C Sardella; L Manetti; I Lupi; C Marcocci; L Bartalena; O Curzio; E Martino; F Bogazzi Journal: J Endocrinol Invest Date: 2016-01-13 Impact factor: 4.256
Authors: R Vervoort; M R Islam; W Sly; A Chabas; R Wevers; J de Jong; I Liebaers; W Lissens Journal: Am J Hum Genet Date: 1995-10 Impact factor: 11.025