RESUMEN
OBJECTIVE: Ultrasonography (US) is the best diagnostic tool for initial assessment of thyroid nodule. Recently, data reporting systems for thyroid lesions, such as the Thyroid Imaging Reporting and Data System (TI-RADS) and American Thyroid Association (ATA), which stratifies the risk for malignancy, have demonstrated good performance in differentiating malignant thyroid nodules. The purpose of this study is to determine the reliability of both data reporting systems in predicting thyroid malignancy in a tertiary care hospital. MATERIALS AND METHODS: We evaluated 195 thyroid nodules using modified TI-RADS and ATA risk stratification. The results were compared to the cyto-pathology analysis. Histopathological results were available for 45 cases after surgery, which is considered the golden standard for diagnosis of thyroid cancer. RESULTS: When compared with cytological results, sensitivity, specificity, negative predictive value (NPV), and accuracy were 100, 61.1, 100, and 63%, respectively, for TI-RADS; and 100, 75, 100, and 76%, respectively, for ATA. When compared with histopathological results, sensitivity, specificity, NPV, and accuracy were 90, 51.4, 94.7, and 60% respectively, for TI-RADS; and 100, 60, 100, and 68%, respectively, for ATA. All patients with malignant nodules were classified in the categories 4 or 5 of TI-RADS and in the intermediate or high suspicion risk according to the ATA system. CONCLUSION: Both TI-RADS and the ATA guidelines have high sensitivity and NPV for the diagnosis of thyroid carcinoma. These systems are feasible for clinical application, allowing to better select patients to undergo fine-needle aspiration biopsies.
Asunto(s)
Medición de Riesgo/métodos , Nódulo Tiroideo/líquido cefalorraquídeo , Nódulo Tiroideo/diagnóstico por imagen , Ultrasonografía/métodos , Anciano , Biopsia con Aguja Fina , Femenino , Humanos , Masculino , Persona de Mediana Edad , Guías de Práctica Clínica como Asunto , Estándares de Referencia , Valores de Referencia , Reproducibilidad de los Resultados , Estudios Retrospectivos , Factores de Riesgo , Sensibilidad y Especificidad , Estadísticas no Paramétricas , Nódulo Tiroideo/patologíaRESUMEN
ABSTRACT Objective Ultrasonography (US) is the best diagnostic tool for initial assessment of thyroid nodule. Recently, data reporting systems for thyroid lesions, such as the Thyroid Imaging Reporting and Data System (TI-RADS) and American Thyroid Association (ATA), which stratifies the risk for malignancy, have demonstrated good performance in differentiating malignant thyroid nodules. The purpose of this study is to determine the reliability of both data reporting systems in predicting thyroid malignancy in a tertiary care hospital. Materials and methods We evaluated 195 thyroid nodules using modified TI-RADS and ATA risk stratification. The results were compared to the cyto-pathology analysis. Histopathological results were available for 45 cases after surgery, which is considered the golden standard for diagnosis of thyroid cancer. Results When compared with cytological results, sensitivity, specificity, negative predictive value (NPV), and accuracy were 100, 61.1, 100, and 63%, respectively, for TI-RADS; and 100, 75, 100, and 76%, respectively, for ATA. When compared with histopathological results, sensitivity, specificity, NPV, and accuracy were 90, 51.4, 94.7, and 60% respectively, for TI-RADS; and 100, 60, 100, and 68%, respectively, for ATA. All patients with malignant nodules were classified in the categories 4 or 5 of TI-RADS and in the intermediate or high suspicion risk according to the ATA system. Conclusion Both TI-RADS and the ATA guidelines have high sensitivity and NPV for the diagnosis of thyroid carcinoma. These systems are feasible for clinical application, allowing to better select patients to undergo fine-needle aspiration biopsies.
Asunto(s)
Humanos , Masculino , Femenino , Persona de Mediana Edad , Anciano , Ultrasonografía/métodos , Nódulo Tiroideo/líquido cefalorraquídeo , Nódulo Tiroideo/diagnóstico por imagen , Medición de Riesgo/métodos , Estándares de Referencia , Valores de Referencia , Reproducibilidad de los Resultados , Estudios Retrospectivos , Factores de Riesgo , Sensibilidad y Especificidad , Nódulo Tiroideo/patología , Guías de Práctica Clínica como Asunto , Estadísticas no Paramétricas , Biopsia con Aguja FinaRESUMEN
Thyroid hormones (TH) are critical regulators of several physiological processes, which include development, differentiation and growth in virtually all tissues. In past decades, several studies have shown that changes in TH levels caused by thyroid dysfunction, disruption of deiodinases and/or thyroid hormone receptor (TR) expression in tumor cells, influence cell proliferation, differentiation, survival and invasion in a variety of neoplasms in a cell type-specific manner. The function of THs and TRs in neoplastic cell proliferation involves complex mechanisms that seem to be cell specific, exerting effects via genomic and nongenomic pathways, repressing or stimulating transcription factors, influencing angiogenesis and promoting invasiveness. Taken together, these observations indicate an important role of TH status in the pathogenesis and/or development of human neoplasia. Here, we aim to present an updated and comprehensive picture of the accumulated knowledge and the current understanding of the potential role of TH status on the different hallmarks of the neoplastic process.
Asunto(s)
Neoplasias/metabolismo , Hormonas Tiroideas/metabolismo , Animales , Humanos , Yoduro Peroxidasa/metabolismo , Microambiente TumoralRESUMEN
BACKGROUND: Thyroid hormone regulates a wide range of cellular activities, including the balance between cell proliferation and differentiation. The thyroid-hormone-inactivating type 3 deiodinase (DIO3, D3) has been shown to be reactivated in human neoplasias. Here, we evaluated DIO3 expression in human papillary thyroid carcinoma (PTC). METHODS: Tumor and surrounding normal thyroid tissue were collected from 26 unselected patients with PTC. Clinical data were retrospectively reviewed in medical records. DIO3 mRNA levels were measured by real-time polymerase chain reaction and D3 activity by paper-descendent chromatography. Studies of DIO3 gene regulation were performed in a human PTC-derived cell line (K1 cells). BRAF(V600E) mutation was identified in DNA from paraffin-embedded tissues by direct sequencing. Immunohistochemistry analyses were performed using a specific human D3 antibody. RESULTS: Increased D3 activity was detected in all 26 PTC samples analyzed as compared with adjacent thyroid tissue. The augmentations in D3 activity were paralleled by increased DIO3 mRNA levels (approximately fivefold). In PTC-derived cells, DIO3 transcripts were further upregulated by the transforming growth factor ß1 (TGFß1). Interestingly, preincubation with mitogen-activated protein kinase (MAPK) cascade inhibitors U0126 (ERK pathway) and SB203580 (p38 pathway) decreased DIO3 mRNA levels and blocked the TGFß1-induced increase in DIO3 transcripts, suggesting that D3 induction might be mediated through the MAPK signaling pathway. Accordingly, DIO3 mRNA and activity levels were significantly higher in BRAF(V600E)-mutated samples (p=0.001). Increased D3 activity was correlated with tumor size (r=0.68, p=0.003), and associated with lymph node (p=0.03) or distant metastasis (p=0.006) at diagnosis. Conversely, decreased levels of the thyroid-hormone-activating type 2 deiodinase (DIO2) gene were observed in PTC, which might contribute to further decreases in intracellular thyroid hormone levels. Increased D3 expression was also observed in follicular thyroid carcinoma but not in medullary or anaplastic thyroid carcinoma samples. CONCLUSIONS: These results indicate that the malignant transformation of thyroid follicular cell toward PTC promotes opposite changes in DIO3 and DIO2 expression by pretranscriptional mechanisms. The association between increased levels of D3 activity and advanced disease further supports a role for intracellular triiodothyronine concentration on the thyroid tumor cell proliferation or/and dedifferentiation.
Asunto(s)
Carcinoma/enzimología , Yoduro Peroxidasa/biosíntesis , Neoplasias de la Tiroides/enzimología , Adulto , Butadienos/farmacología , Carcinoma Papilar , Línea Celular Tumoral , Niño , Inhibidores Enzimáticos/farmacología , Femenino , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Humanos , Imidazoles/farmacología , Inmunohistoquímica , Yoduro Peroxidasa/análisis , Sistema de Señalización de MAP Quinasas/efectos de los fármacos , Sistema de Señalización de MAP Quinasas/fisiología , Masculino , Persona de Mediana Edad , Mutación , Nitrilos/farmacología , Proteínas Proto-Oncogénicas B-raf/genética , Piridinas/farmacología , Estudios Retrospectivos , Cáncer Papilar Tiroideo , Factor de Crecimiento Transformador beta1/metabolismo , Adulto JovenRESUMEN
Thyroid hormone is essential for the normal function of virtually all tissues. The iodothyronine deiodinases catalyze the removal of an iodine residue from the pro-hormone thyroxine (T(4)) molecule, thus producing either the active form triiodothyronine (T(3); activation) or inactive metabolites (reverse T(3); inactivation). Type I deiodinase (D1) catalyzes both reactions. Over the last years, several studies have attempted to understand the mechanisms of D1 function, underlying its effects on normal thyroid hormone metabolism and pathological processes. Although peripheral D1-generated T(3) production contributes to a portion of plasma T(3) in euthyroid state, pathologically increased thyroidal D1 activity seems to be the main cause of the elevated T(3) concentrations observed in hyperthyroid patients. On the other hand, D1-deficient mouse models show that, in the absence of D1, inactive and lesser iodothyronines are excreted in feces with the loss of associated iodine, demonstrating the scavenging function for D1 that might be particularly important in an iodine deficiency setting. Polymorphisms in the DIO1 gene have been associated with changes in serum thyroid hormone levels, whereas decreased D1 activity has been reported in the nonthyroid illness syndrome and in several human neoplasias. The current review aims at presenting an updated picture of the recent advances made in the biochemical and molecular properties of D1 as well as its role in human physiology.
Asunto(s)
Yoduro Peroxidasa/metabolismo , Enfermedad/etiología , Humanos , Yoduro Peroxidasa/genética , Hormonas Tiroideas/sangre , Hormonas Tiroideas/metabolismoRESUMEN
OBJECTIVE: The aim of this study was to evaluate the accuracy of the measurement of thyroglobulin in washout needle aspiration biopsy (FNAB-Tg) to detect papillary thyroid cancer (PTC) metastases. SUBJECTS AND METHODS: Forty-three patients (51.4 ± 14.6 years) with PTC diagnosis and evidence of enlarged cervical lymph nodes (LN) were included. An ultrasound-guided fine-needle aspiration of suspicious LN was performed, for both cytological examination and measurement of FNAB-Tg. RESULTS: The median values of FNAB-Tg in patients with metastatic LN (n = 5) was 3,419 ng/mL (11.1-25,538), while patients without LN metastasis (n = 38) showed levels of 3.7 ng/mL (0.8-7.4). Considering a 10 ng/mL cutoff value for FNAB-Tg, the sensitivity and specificity was 100%. There were no differences on the median of FNAB-Tg measurements between those on (TSH 0.07 mUI/mL) or off levothyroxine (TSH 97.4 mUI/mL) therapy (3.3 vs. 3.8 ng/mL, respectively; P = 0.2). CONCLUSION: The results show that evaluation of FNAB-Tg in cervical LN is a valuable diagnostic tool for PTC metastases that can be used independent of the thyroid status.
Asunto(s)
Biomarcadores de Tumor/análisis , Biopsia con Aguja Fina/métodos , Carcinoma Papilar/diagnóstico , Ganglios Linfáticos/química , Tiroglobulina/análisis , Neoplasias de la Tiroides/diagnóstico , Adulto , Anciano , Carcinoma , Carcinoma Papilar/secundario , Femenino , Humanos , Ganglios Linfáticos/patología , Metástasis Linfática/diagnóstico , Masculino , Persona de Mediana Edad , Cuello , Sensibilidad y Especificidad , Cáncer Papilar Tiroideo , Neoplasias de la Tiroides/secundario , Tirotropina/fisiologíaRESUMEN
OBJECTIVE: The aim of this study was to evaluate the accuracy of the measurement of thyroglobulin in washout needle aspiration biopsy (FNAB-Tg) to detect papillary thyroid cancer (PTC) metastases. SUBJECTS AND METHODS: Forty-three patients (51.4 ± 14.6 years) with PTC diagnosis and evidence of enlarged cervical lymph nodes (LN) were included. An ultrasound-guided fine-needle aspiration of suspicious LN was performed, for both cytological examination and measurement of FNAB-Tg. RESULTS: The median values of FNAB-Tg in patients with metastatic LN (n = 5) was 3,419 ng/mL (11.1-25,538), while patients without LN metastasis (n = 38) showed levels of 3.7 ng/mL (0.8-7.4). Considering a 10 ng/mL cutoff value for FNAB-Tg, the sensitivity and specificity was 100 percent. There were no differences on the median of FNAB-Tg measurements between those on (TSH 0.07 mUI/mL) or off levothyroxine (TSH 97.4 mUI/mL) therapy (3.3 vs. 3.8 ng/mL, respectively; P = 0.2). CONCLUSION: The results show that evaluation of FNAB-Tg in cervical LN is a valuable diagnostic tool for PTC metastases that can be used independent of the thyroid status.
OBJETIVO: O objetivo deste estudo foi avaliar a acurácia da dosagem de tireoglobulina no lavado da agulha da punção aspirativa (PAAF-Tg) de linfonodos (LN) cervicais para detecção de metástases do câncer papilar de tireoide (CPT). SUJEITOS E MÉTODOS: Foram incluídos 43 pacientes (51,4 ± 14,6 anos) com diagnóstico de CPT e evidência de LN cervicais aumentados. Os LN suspeitos foram submetidos à punção aspiração com agulha fina guiada por ecografia para análise citológica e dosagem de tireoglobulina (PAAF-Tg). RESULTADOS: A mediana dos valores de PAAF-Tg nos LN metastáticos (n = 5) foi 3.419,0 ng/mL (11,1-25.538), enquanto nos LN não metastáticos (n= 38) a mediana foi de 3,7 ng/mL (0,8-7,4). Utilizando-se o nível de 10 ng/mL como ponto de corte, observaram-se sensibilidade e especificidade de 100 por cento. Os níveis de TSH sérico não interferiram na dosagem de PAAF-Tg (3,3 e 3,8 ng/mL nos grupos com TSH supresso (TSH 0,07 mUI/mL) e hipotireoidismo (TSH 97,4 mUI/mL), respectivamente, P = 0,2). CONCLUSÃO: Os resultados demonstram que a dosagem de PAAF-Tg é uma ferramenta importante no diagnóstico de metástases do CPT, podendo ser utilizada independente do "status" tireoidiano.
Asunto(s)
Adulto , Anciano , Femenino , Humanos , Masculino , Persona de Mediana Edad , Biopsia con Aguja Fina/métodos , Carcinoma Papilar/diagnóstico , Ganglios Linfáticos/química , Tiroglobulina/análisis , Neoplasias de la Tiroides/diagnóstico , Biomarcadores de Tumor/análisis , Carcinoma Papilar/secundario , Ganglios Linfáticos/patología , Metástasis Linfática/diagnóstico , Cuello , Sensibilidad y Especificidad , Neoplasias de la Tiroides/secundario , Tirotropina/fisiologíaRESUMEN
Multiple endocrine neoplasia type 2A (MEN2A) is an autosomal dominant inherited condition that predisposes to the triad of medullary thyroid cancer (MTC), pheochromocytoma (Pheo), and primary hyperparathyroidism (PHT). Nearly 100 percent of MEN2A are associated with germ line mutation of the RET proto-oncogene (RET), and DNA-based RET genotype analysis is now considered essential for earlier diagnosis. The first manifestation of MEN2A is most often due to MTC, and less frequently to Pheo. Rarely, MEN2A is recognized during the search for PHT associated conditions. Most patients with primary hyperparathyroidism are asymptomatic, and the focus of the presentation may be the side effects of chronic hypercalcemia, osteoporosis, renal lithiasis, peptic ulcer disease, and hypertension. Hypercalcemic pancreatitis is rare, being an uncommon first manifestation of PHT. Here, we report on a patient who presented recurrent pancreatitis as the first manifestation of MEN2A. In the present case, prompt sequential dosage of calcium, diagnosis of PHT, and genetic analysis would have resulted in pancreatitis prevention and early MEN2A management.
Neoplasia endócrina múltipla do tipo 2 (NEM2A) é uma síndrome genética com herança autossômica dominante, que predispõe à tríade de carcinoma medular de tireóide (CMT), feocromocitoma (Feo) e hiperparatireoidismo primário (HPP). Aproximadamente 100 por cento dos casos de NEM2A estão associados a mutações germinativas do protooncogene RET (RET), e a análise molecular do RET é atualmente considerada essencial para diagnóstico precoce. A primeira manifestação da NEM2A é geralmente em decorrência de CMT, e menos freqüentemente devido ao Feo. Raramente, a NEM2A é descoberta durante investigação para condições associadas ao HPP. A maioria dos pacientes com HPP é oligossintomática e a apresentação ocorre devido a sintomas relacionados à hipercalcemia, à osteoporose, à dispepsia, à hipertensão ou à litíase renal. A pancreatite hipercalcêmica é rara, sendo uma manifestação incomum do HPP. Este artigo relata um caso de paciente que apresentou pancreatite recorrente como primeira manifestação de NEM2A. Neste caso, abordagem seqüencial com determinação do cálcio sérico, diagnóstico de HPP e análise genética poderiam ter resultado prevenção de pancreatite e manejo precoce da NEM2A.
Asunto(s)
Humanos , Masculino , Persona de Mediana Edad , Hiperparatiroidismo Primario/complicaciones , /complicaciones , Pancreatitis/etiología , Proteínas Proto-Oncogénicas c-ret/genética , Enfermedad Aguda , Calcio/sangre , Mutación de Línea Germinal/genética , Pancreatitis/diagnósticoRESUMEN
Type II deiodinase (D2) plays a critical role in controlling intracellular T3 concentration and early studies indicated a follicular but not a parafollicular C-cell origin of D2 activity in the thyroid gland. Here, we show that D2 is highly expressed in human medullary thyroid carcinoma (MTC), a tumor that arises from the C-cells. D2 transcripts were detected in all MTC samples obtained from 12 unselected MTC patients and the levels of D2 activity were comparable to those found in surrounding normal follicular tissue (0.41+/-0.10 fmol min mg protein vs. 0.43+/-0.41 fmol min mg protein, P=0.91). Additional analysis in the TT cells, a human MTC cell line, demonstrated that the D2 expression is downregulated by thyroid hormones and enhanced by cAMP analogs and dexamethasone. The thyroid hormone receptor alpha1 and beta isoforms were also detected in all MTC samples and in TT cells, thus suggesting a potential role of T3 locally produced by D2 in this neoplastic tissue.
Asunto(s)
Carcinoma Medular/enzimología , Yoduro Peroxidasa/biosíntesis , Neoplasias de la Tiroides/enzimología , Adulto , Carcinoma Medular/patología , Línea Celular Tumoral , AMP Cíclico/farmacología , Femenino , Regulación Enzimológica de la Expresión Génica/efectos de los fármacos , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Humanos , Masculino , Persona de Mediana Edad , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Hormonas Tiroideas/metabolismo , Hormonas Tiroideas/farmacología , Neoplasias de la Tiroides/patología , Adulto Joven , Yodotironina Deyodinasa Tipo IIRESUMEN
Multiple endocrine neoplasia type 2A (MEN2A) is an autosomal dominant inherited condition that predisposes to the triad of medullary thyroid cancer (MTC), pheochromocytoma (Pheo), and primary hyperparathyroidism (PHT). Nearly 100% of MEN2A are associated with germ line mutation of the RET proto-oncogene (RET), and DNA-based RET genotype analysis is now considered essential for earlier diagnosis. The first manifestation of MEN2A is most often due to MTC, and less frequently to Pheo. Rarely, MEN2A is recognized during the search for PHT associated conditions. Most patients with primary hyperparathyroidism are asymptomatic, and the focus of the presentation may be the side effects of chronic hypercalcemia, osteoporosis, renal lithiasis, peptic ulcer disease, and hypertension. Hypercalcemic pancreatitis is rare, being an uncommon first manifestation of PHT. Here, we report on a patient who presented recurrent pancreatitis as the first manifestation of MEN2A. In the present case, prompt sequential dosage of calcium, diagnosis of PHT, and genetic analysis would have resulted in pancreatitis prevention and early MEN2A management.
Asunto(s)
Hiperparatiroidismo Primario/complicaciones , Neoplasia Endocrina Múltiple Tipo 2a/complicaciones , Pancreatitis/etiología , Proteínas Proto-Oncogénicas c-ret/genética , Enfermedad Aguda , Calcio/sangre , Mutación de Línea Germinal/genética , Humanos , Masculino , Persona de Mediana Edad , Pancreatitis/diagnóstico , Proto-Oncogenes MasRESUMEN
The iodothyronine deiodinases constitute a family of selenoenzymes that catalyze the removal of iodine from the outer ring or inner ring of the thyroid hormones. The activating enzymes, deiodinases type I (D1) and type II (D2), are highly expressed in normal thyroid gland. Benign or malignant neoplastic transformation of the thyroid cells is associated with changes on the expression of these enzymes, suggesting that D1 or D2 can be markers of cellular differentiation. Abnormalities on the expression of both enzymes and also of the deiodinase type III (D3), that inactivates thyroid hormones, have been found in other human neoplasias. So far, the mechanism or implications of these findings on tumor pathogenesis are not well understood. Nevertheless, its noteworthy that abnormal expression of D2 can cause thyrotoxicosis in patients with metastasis of follicular thyroid carcinoma and that increased D3 expression in large hemangiomas causes severe hypothyroidism.
Asunto(s)
Carcinoma Papilar/enzimología , Yoduro Peroxidasa/metabolismo , Neoplasias de la Tiroides/enzimología , Biomarcadores de Tumor/metabolismo , Carcinoma Papilar/genética , Regulación Enzimológica de la Expresión Génica/fisiología , Hemangioma/enzimología , Hemangioma/genética , Humanos , ARN Mensajero/genética , ARN Mensajero/metabolismo , Glándula Tiroides/enzimología , Neoplasias de la Tiroides/genética , Tiroxina/metabolismo , Triyodotironina/metabolismo , Yodotironina Deyodinasa Tipo IIRESUMEN
As iodotironinas desiodases formam uma família de selenoenzimas com propriedades catalíticas distintas que ativam ou inativam os hormônios tireoidianos via desiodação do anel fenólico ou tirosínico da molécula do T4. As desiodases tipo I e II (D1 e D2) são as enzimas responsáveis pela geração do T3 e são amplamente expressas na tireóide normal. A transformação neoplásica benigna ou maligna da glândula tireóide está associada a alterações na expressão dessas isoenzimas, sugerindo um possível papel da D1 e da D2 como marcadores de diferenciação celular. Anormalidades na expressão de ambas enzimas e da desiodase tipo III (D3), inativadora do hormônios tireoidianos, são também encontradas em outras neoplasias humanas. Os mecanismos ou implicações do aumento ou diminuição das desiodases na patogênese neoplásica são pouco compreendidas. No entanto, é importante observar que a expressão anormal da D2 pode ser responsável por um quadro de tireotoxicose em pacientes com metástases de carcinoma folicular de tireóide, enquanto que o aumento da D3 em hemangiomas pode causar hipotireoidismo de difícil tratamento.
The iodothyronine deiodinases constitute a family of selenoenzymes that catalyze the removal of iodine from the outer ring or inner ring of the thyroid hormones. The activating enzymes, deiodinases type I (D1) and type II (D2), are highly expressed in normal thyroid gland. Benign or malignant neoplastic transformation of the thyroid cells is associated with changes on the expression of these enzymes, suggesting that D1 or D2 can be markers of cellular differentiation. Abnormalities on the expression of both enzymes and also of the deiodinase type III (D3), that inactivates thyroid hormones, have been found in other human neoplasias. So far, the mechanism or implications of these findings on tumor pathogenesis are not well understood. Nevertheless, its noteworthy that abnormal expression of D2 can cause thyrotoxicosis in patients with metastasis of follicular thyroid carcinoma and that increased D3 expression in large hemangiomas causes severe hypothyroidism.
Asunto(s)
Humanos , Carcinoma Papilar/enzimología , Yoduro Peroxidasa/metabolismo , Neoplasias de la Tiroides/enzimología , Carcinoma Papilar/genética , Regulación Enzimológica de la Expresión Génica/fisiología , Hemangioma/enzimología , Hemangioma/genética , ARN Mensajero/genética , ARN Mensajero/metabolismo , Glándula Tiroides/enzimología , Neoplasias de la Tiroides/genética , Tiroxina/metabolismo , Triyodotironina/metabolismo , Biomarcadores de Tumor/metabolismoRESUMEN
The single-nucleotide polymorphism A/G in the type 2 deiodinase (D2) gene predicts a threonine (Thr) to alanine (Ala) substitution at codon 92 (D2 Thr92Ala) and is associated with insulin resistance in obese patients. Here, this association was investigated in 183 patients with type 2 diabetes mellitus, using homeostasis model assessment. The median fasting plasma insulin in Ala/Ala individuals was significantly higher than in patients with Ala/Thr or Thr/Thr genotypes (19.6 vs. 12.0 vs. 14.8 mIU/ml, respectively; P = 0.004). Assuming a recessive model, the homeostasis model assessment index was higher in the Ala/Ala group when compared with Ala/Thr-Thr/Thr group (8.50 vs. 4.85, P = 0.003). Although this polymorphism has not been associated with changes in D2 kinetics as measured in HEK-293 cells transiently expressing D2 Thr92Ala, we investigated whether such association could be detected in human tissue samples. Remarkably, in thyroid and skeletal muscle samples from subjects homozygous for the Ala allele, D2 velocity was significantly lower than in subjects with Ala/Thr-Thr/Thr genotypes (P = 0.05 and 0.04, respectively). In conclusion, the A/G polymorphism is associated with greater insulin resistance in type 2 diabetes mellitus patients and with lower D2 velocity in tissue samples. These findings suggest that the D2-generated T(3) in skeletal muscle plays a role in insulin resistance.