RESUMO
Congenital hypothyroidism (CH) due to thyroglobulin (TG) variants causes very low serum TG levels with normal or enlarged thyroid glands, depending on the severity of the defect, and with autosomal recessive inheritance. The purpose of this study was to functionally characterize p.Cys1281Tyr variant in the TG gene in order to increase our knowledge of the molecular mechanisms associated with CH. In order to find evidence that support the hypothesis that the p.Cys1281Tyr variant would affect the TG folding were performed amino acid prediction, 3D modeling and transient expression analysis in HEK293T cells. 18 of the 21â³in silico" algorithms predict a deleterious effect of the p.Cys1281Tyr variant. The full-length 3D model p.Cys1281Tyr TG showed disulfide bond cleavage between the cysteines at positions 1249 and 1281 and rearrangement of the TG structure, while transient expression analysis indicated that p.Cys1281Tyr causes retention of the protein inside the cell. Consequently, these results show that this pathogenic variant makes it impossible for TG to fulfill its function in the biosynthesis process of thyroid hormones, causing CH. In conclusion, our results confirm the pathophysiological importance of misfolding of TG as a consequence of p.Cys1281Tyr variant located in the hinge module/flap region of TG.
Assuntos
Hipotireoidismo Congênito , Bócio , Humanos , Hipotireoidismo Congênito/genética , Tireoglobulina/genética , Tireoglobulina/metabolismo , Células HEK293 , Bócio/genética , Hormônios TireóideosRESUMO
Thyroglobulin (TG), the predominant glycoprotein of the thyroid gland, functions as matrix protein in thyroid hormonegenesis. TG deficiency results in thyroid dyshormonogenesis. These variants produce a heterogeneous spectrum of congenital goitre, with an autosomal recessive mode of inheritance. The purpose of this study was to identify and functionally characterize new variants in the TG gene in order to increase the understanding of the molecular mechanisms responsible for thyroid dyshormonogenesis. A total of four patients from two non-consanguineous families with marked alteration of TG synthesis were studied. The two families were previously analysed in our laboratory, only one deleterious allele, in each one, was detected after sequencing the TG gene (c.2359 C > T [p.Arg787*], c.5560 G > T [p.Glu1854*]). These findings were confirmed in the present studies by Next-Generation Sequencing. The single nucleotide coding variants of the TG gene were then analyzed to predict the possible variant causing the disease. The p.Pro2232Leu (c.6695 C > T), identified in both families, showing a low frequency population in gnomAD v2.1.1 database and protein homology, amino acid prediction, and 3D modeling analysis predict a potential pathogenic effect of this variant. We also transiently express p.Pro2232Leu in a full-length rat TG cDNA clone and confirmed that this point variant was sufficient to cause intracellular retention of mutant TG in HEK293T cells. Consequently, each family carried a compound heterozygous for p.Arg787*/p.Pro2232Leu or p.Glu1854*/p.Pro2232Leu variants. In conclusion, our results confirm the pathophysiological importance of altered TG folding as a consequence of missense variants located in the ChEL domain of TG.
Assuntos
Hipotireoidismo Congênito , Bócio , Animais , Humanos , Ratos , Hipotireoidismo Congênito/genética , Células HEK293 , Tireoglobulina/genética , Tireoglobulina/metabolismo , Transporte Proteico/genéticaRESUMO
Thyroglobulin (TG) plays a main role in the biosynthesis of thyroid hormones (TH), and, thus, it is involved in a wide range of vital functions throughout the life cycle of all vertebrates. Deficiency of TH production due to TG genetic variants causes congenital hypothyroidism (CH), with devastating consequences such as intellectual disability and impaired growth if untreated. To this day, 229 variations in the human TG gene have been identified while the 3D structure of TG has recently appeared. Although TG deficiency is thought to be of autosomal recessive inheritance, the introduction of massive sequencing platforms led to the identification of a variety of monoallelic TG variants (combined with mutations in other thyroid gene products) opening new questions regarding the possibility of oligogenic inheritance of the disease. In this review we discuss remarkable advances in the understanding of the TG architecture and the pathophysiology of CH associated with TG defects, providing new insights for the management of congenital disorders as well as counseling benefits for families with a history of TG abnormalities. Moreover, we summarize relevant aspects of TH synthesis within TG and offer an updated analysis of animal and cellular models of TG deficiency for pathophysiological studies of thyroid dyshormonogenesis while highlighting perspectives for new investigations. All in all, even though there has been sustained progress in understanding the role of TG in thyroid pathophysiology during the past 50 years, functional characterization of TG variants remains an important area of study for future advancement in the field.
Assuntos
Hipotireoidismo Congênito/genética , Variação Genética , Tireoglobulina/química , Tireoglobulina/genética , Animais , Humanos , Modelos Moleculares , Conformação Proteica , Tireoglobulina/metabolismo , Hormônios Tireóideos/metabolismoRESUMO
Thyroid carcinomas are a common form of endocrine neoplasia in dogs. In the present study, we combined histopathology with immunohistochemistry (IHC) to search for the presence of oestrogen receptor alpha (ORα), Cox-2 and Ki67 in canine thyroid carcinomas. Forty-eight thyroid carcinomas were diagnosed throughout the study period. Thyroglobulin and calcitonin IHC distinguished between thyroid tumours with a follicular and medullary (C-cell) origin, respectively. IHC-based diagnosis showed that 42 (87.50%) of the cases were follicular cell carcinoma. In these cases, the follicular-compact pattern was the most frequent (n = 20/42; 47.62%) and six cases (12.5%) were medullary cell (C-cell) carcinomas. Both medullary (C-cell) and follicular carcinomas expressed Ki67 and Cox-2. No differences were observed between medullary and follicular carcinomas with respect to expression of Ki67 (P = 0.34) and Cox-2 (P = 0.9523) markers. A total of 4.17% (n = 2/48) of thyroid carcinomas showed positive nuclear labelling for ORα, suggesting that oestrogen does not directly participate in the pathogenesis of canine thyroid neoplasia.
Assuntos
Doenças do Cão , Neoplasias da Glândula Tireoide/veterinária , Adenocarcinoma Folicular/patologia , Adenocarcinoma Folicular/veterinária , Animais , Biomarcadores Tumorais/metabolismo , Calcitonina/metabolismo , Carcinoma Neuroendócrino/patologia , Carcinoma Neuroendócrino/veterinária , Diagnóstico Diferencial , Cães , Neoplasias das Glândulas Endócrinas/veterinária , Imuno-Histoquímica/veterinária , Tireoglobulina/metabolismo , Neoplasias da Glândula Tireoide/patologiaRESUMO
Thyroid hormones play an important role in glucose metabolism and there is evidence of increased prevalence of thyroid dysfunction in obese and diabetic patients. This study aimed at evaluating the thyroid function and the effects of the triiodothyronine (T3) treatment on glycemia control, insulin sensitivity and subclinical inflammation in cafeteria-diet-induced obesity in rats. Obesity was induced in male Wistar rats by offering a cafeteria diet and a subset of the obese rats was treated with T3 (1.5 µg per 100 g of body weight) for a 28-day period. The pituitary-thyroid axis was evaluated by molecular and biochemical parameters. Cytokine content was measured in the serum as well as in the mesenteric and epididymal white adipose tissue. Obese rats exhibited impairment of glycemia control, increased content of inflammatory cytokines in mesenteric white adipose tissue, decreased serum thyrotropin (TSH) concentration and increased sodium/iodide symporter (NIS) and TSH receptor (TSHR) protein content in thyroid gland. T3 treatment improved insulin sensitivity, glucose tolerance, and reduced inflammatory cytokine content in mesenteric white adipose tissue. In the thyroid gland NIS, TSHR, and thyroperoxidase (TPO) content were reduced while thyroglobulin (TG) content was increased by T3. The thyrotrophic response to negative feedback exerted by T3 was preserved in obese rats. The present data reinforce the beneficial effects of T3 treatment of obese rats on the improvement of insulin sensitivity and on the negative modulation of inflammatory cytokine expression in adipose tissue. Moreover, we have evidenced that the pituitary-thyroid axis is affected in obese rats, as illustrated by the impaired TSH secretion.
Assuntos
Tecido Adiposo/efeitos dos fármacos , Citocinas/sangue , Resistência à Insulina , Obesidade/metabolismo , Tri-Iodotironina/farmacologia , Tecido Adiposo/metabolismo , Animais , Glicemia/metabolismo , Citocinas/metabolismo , Retroalimentação Fisiológica , Masculino , Ratos , Ratos Wistar , Receptores da Tireotropina/metabolismo , Simportadores/metabolismo , Tireoglobulina/metabolismo , Glândula Tireoide/efeitos dos fármacos , Glândula Tireoide/metabolismo , Tireotropina/sangueRESUMO
BACKGROUND: Serum thyroglobulin (Tg) is the key parameter used in the follow-up of subjects with differentiated thyroid cancer (DTC). Current guidelines advise its measurement to take place when Thyrotropin (TSH) levels are >30 µU/ml (stimulated Tg) and when TSH < 0.1 µU/ml (suppressed Tg). Although stimulated Tg levels <1 ng/ml have been shown to display excellent prognosis, relapses may occur despite low Tg levels. Recently, very low cut-off levels of stimulated Tg have been proposed for determining the recurrence risk in these subjects. In this study, we aimed to assess the association between ablative stimulated Tg obtained before radioactive iodine ablation therapy (RAI) (ASTg) and late stimulated Tg obtained 6-12 months after primary therapy (LSTg) in a group of subjects with DTC. We also aimed to establish a cut-off level of Tg for recurrence. METHODS: We retrospectively analyzed 393 subjects with low or intermediate risk DTC diagnosed at our institution between January 2000 and December 2010 with a mean follow-up period of 64.4 months (range 14-192 months). All stimulated Tg levels were performed following levothyroxine withdrawal in this study. RESULTS: Histopathological analysis indicated papillary carcinoma in 362 (92.1%) subjects and follicular carcinoma in 31 (7.9%) subjects. Three hundred and twenty-four (82.4%) of our cases were females, and 69 (17.6%) were males. Recurrence occurred in 82 (20.9%) of the subjects. Relapse was significantly more frequently observed in subjects with ASTg ≥ 2 ng/ml; and LSTg ≥ 2 ng/ml. (p = 0.004 and p < 0.001, respectively). In subjects negative for thyroglobulin antibodies (Tg-ab), an ASTg value ≥5.6 ng/ml was established to increase the risk of recurrence by 2.38-fold (p = 0.002), whereas an LSTg ≥ 0.285 ng/ml increased the risk of relapse by 3.087-fold (p < 0.001). CONCLUSION: As a result of this study, we determined that the optimum cut-off level for both ASTg and LSTg may be lower than those previously reported. Using such a lower cut-off may improve sensitivity for detecting relapse.
Assuntos
Adenocarcinoma Folicular/tratamento farmacológico , Autoanticorpos/sangue , Carcinoma Papilar/tratamento farmacológico , Recidiva Local de Neoplasia/induzido quimicamente , Tireoglobulina/metabolismo , Neoplasias da Glândula Tireoide/tratamento farmacológico , Tiroxina/efeitos adversos , Adenocarcinoma Folicular/patologia , Carcinoma Papilar/patologia , Ablação por Cateter , Feminino , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Recidiva Local de Neoplasia/diagnóstico , Recidiva Local de Neoplasia/metabolismo , Prognóstico , Estudos Retrospectivos , Taxa de Sobrevida , Neoplasias da Glândula Tireoide/patologia , Suspensão de TratamentoRESUMO
AIM: This study evaluated the long-term results of ablation with low iodine-131 (131I) activity in patients with papillary thyroid carcinoma (PTC) with a lower risk of recurrence and who remained with nonstimulated thyroglobulin (Tg) of at least 0.3 ng/ml after total thyroidectomy. METHODS: This was a prospective study including 119 patients with PTC (except for microcarcinoma restricted to the thyroid and tumor with extensive extrathyroidal extension, aggressive histology, extensive lymph node involvement, or known residual disease). After thyroidectomy, all patients had nonstimulated Tg of at least 0.3 ng/ml (range: 0.3-8.5 ng/ml). The patients were treated with low 131I activity (30 or 50 mCi). RESULTS: Post-therapy whole-body scanning showed ectopic uptake in two patients. When evaluated 12 months after ablation, nonstimulated Tg up to 0.2 ng/ml with negative antithyroglobulin antibodies and neck ultrasonography, defined as excellent response to initial therapy, was achieved in 92 patients (77.3%). Only one patient had persistent structural disease. During follow-up, 3/118 patients (2.5%) developed structural recurrence. In the last assessment, 102/115 patients who were not subjected to any additional therapy had nonstimulated Tg up to 0.2 ng/ml, negative antithyroglobulin antibodies, and ultrasonography with no anomalies. No death occurred because of the tumor. CONCLUSIONS: Postoperative nonstimulated Tg up to 2 ng/ml had a negative predictive value of 98% for recurrent or persistent structural disease. In patients with PTC who have a lower risk of recurrence and who remain with nonstimulated Tg of at least 0.3 ng/ml after total thyroidectomy, Tg up to 2 ng/ml can be used as a criterion for ablation with low 131I activity.
Assuntos
Técnicas de Ablação , Carcinoma/metabolismo , Carcinoma/terapia , Radioisótopos do Iodo/uso terapêutico , Tireoglobulina/metabolismo , Neoplasias da Glândula Tireoide/metabolismo , Neoplasias da Glândula Tireoide/terapia , Adolescente , Adulto , Idoso , Carcinoma/cirurgia , Carcinoma Papilar , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Período Pós-Operatório , Valor Preditivo dos Testes , Recidiva , Câncer Papilífero da Tireoide , Neoplasias da Glândula Tireoide/cirurgia , Fatores de Tempo , Adulto JovemRESUMO
Thyroglobulin (Tg) is the major glycoprotein produced by the thyroid gland, where it serves as a template for thyroid hormone synthesis and as an intraglandular store of iodine. Measurement of Tg levels in serum is of great practical importance in the follow-up of differentiated thyroid carcinoma (DTC), a setting in which elevated levels after total thyroidectomy are indicative of residual or recurrent disease. The most recent methods for serum Tg measurement are monoclonal antibody-based and are highly sensitive. However, major challenges remain regarding the interpretation of the results obtained with these immunometric methods, particularly in patients with endogenous antithyroglobulin antibodies or in the presence of heterophile antibodies, which may produce falsely low or high Tg values, respectively. The increased prevalence of antithyroglobulin antibodies in patients with DTC, as compared with the general population, raises the very pertinent possibility that tumor Tg may be more immunogenic. This inference makes sense, as the tumor microenvironment (tumor cells plus normal host cells) is characterized by several changes that could induce posttranslational modification of many proteins, including Tg. Attempts to understand the structure of Tg have been made for several decades, but findings have generally been incomplete due to technical hindrances to analysis of such a large protein (660 kDa). This review article will explore the complex structure of Tg and the potential role of its marked heterogeneity in our understanding of normal thyroid biology and neoplastic processes.
Assuntos
Processamento de Proteína Pós-Traducional , Tireoglobulina/metabolismo , Doenças da Glândula Tireoide , Biomarcadores Tumorais/sangue , Glicosilação , Halogenação , Humanos , Fosforilação , Tireoglobulina/química , Doenças da Glândula Tireoide/sangue , Doenças da Glândula Tireoide/diagnóstico , Doenças da Glândula Tireoide/etiologia , Doenças da Glândula Tireoide/prevenção & controle , Hormônios Tireóideos/biossínteseRESUMO
ABSTRACT Thyroglobulin (Tg) is the major glycoprotein produced by the thyroid gland, where it serves as a template for thyroid hormone synthesis and as an intraglandular store of iodine. Measurement of Tg levels in serum is of great practical importance in the follow-up of differentiated thyroid carcinoma (DTC), a setting in which elevated levels after total thyroidectomy are indicative of residual or recurrent disease. The most recent methods for serum Tg measurement are monoclonal antibody-based and are highly sensitive. However, major challenges remain regarding the interpretation of the results obtained with these immunometric methods, particularly in patients with endogenous antithyroglobulin antibodies or in the presence of heterophile antibodies, which may produce falsely low or high Tg values, respectively. The increased prevalence of antithyroglobulin antibodies in patients with DTC, as compared with the general population, raises the very pertinent possibility that tumor Tg may be more immunogenic. This inference makes sense, as the tumor microenvironment (tumor cells plus normal host cells) is characterized by several changes that could induce posttranslational modification of many proteins, including Tg. Attempts to understand the structure of Tg have been made for several decades, but findings have generally been incomplete due to technical hindrances to analysis of such a large protein (660 kDa). This review article will explore the complex structure of Tg and the potential role of its marked heterogeneity in our understanding of normal thyroid biology and neoplastic processes.
Assuntos
Humanos , Processamento de Proteína Pós-Traducional , Doenças da Glândula Tireoide , Tireoglobulina/metabolismo , Biomarcadores Tumorais/sangue , Glicosilação , Halogenação , Fosforilação , Tireoglobulina/química , Doenças da Glândula Tireoide/sangue , Doenças da Glândula Tireoide/diagnóstico , Doenças da Glândula Tireoide/etiologia , Doenças da Glândula Tireoide/prevenção & controle , Hormônios Tireóideos/biossínteseRESUMO
Immunoreactive proteins in follicular cells, fibroblasts and endothelial cells were assessed in canine thyroid carcinomas and healthy thyroid glands. No differences were detected in thyrotropin receptor and thyroglobulin staining between cancer and normal tissues, but expression was higher in follicular cells than in fibroblasts. Fibroblast growth factor-2 staining was more intense in healthy follicular cells than in those of carcinomas. Follicular cells in carcinomas presented two- to three-fold greater staining intensity of thyroid transcription factor-1 and proliferating cell nuclear antigen, respectively, than healthy cells, and a similar trend was found for the latter antigen in fibroblasts. Vascular endothelial growth factor staining was more intense in the endothelial cells of tumours than in those of normal tissues. In conclusion, greater expression of factors related to proliferation and angiogenesis was demonstrated in several cell types within thyroid carcinomas compared to healthy tissues, which may represent mechanisms of tumour progression in this disease.