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Medullary thyroid carcinoma (MTC) occurs in a sporadic or as an autosomal dominant hereditary form. Inherited forms of MTC are related to mutations in the RET proto-oncogene. We screened genomic DNA from 11 patients with MTC for mutations in exons 10, 11, 13, 14, 15, and 16 of the RET proto-oncogene. Subsequently, we also evaluated a family of 1 patient with presumed diagnosis of sporadic MTC. Three patients with MEN2A from two unrelated families presented mutations in exon 11 (C634Y and C634R). A heterozygous mutation in exon 14 (V804M) was identified in the patient with the presumed sporadic MTC. We also observed two different polymorphisms: S904S in exon 15 (2 patients) and L769L in exon 13 (4 patients). The L769L polymorphism has been associated with earlier onset of sporadic MTC. On the other hand, mutations in exon 14 are associated with MTC of later onset and lower aggressiveness. Indeed, the carrier of the V804M mutation associated with L769L polymorphism presented MTC at 32 years of age, in contrast to her asymptomatic mother, who had only the V804M mutation and had MTC diagnosed by fine-needle aspiration biopsy at 60 years of age. In conclusion, the present study confirms the need for genetic screening to differentiate sporadic and hereditary forms of MTC. In addition, the genetic study allows the identification of asymptomatic carriers of hereditary forms of MTC. Finally, we speculated that the L769L polymorphism of the RET proto-oncogene may be related to earlier age of onset in the patient with the V804M mutation.

BackgroundStructural myocardial abnormalities have been extensively documented in hypothyroidism. Experimental studies in animal models have also shown involvement of thyroid hormones in gene expression of myocardial collagen. This study was planned to investigate the ability of ultrasonic tissue characterization, as evaluated by integrated backscatter (IBS), to early identify myocardial involvement in thyroid dysfunction.Patients and MethodsWe studied 15 patients with hyperthyroidism (HYPER), 8 patients with hypothyroidism (HYPO), 14 patients with subclinical hypothyroidism (SCH) and 19 normal (N) subjects, who had normal LV systolic function. After treatment, 10 HYPER, 6 HYPO, and 8 SCH patients were reevaluated. IBS images were obtained and analyzed in parasternal short axis (papillary muscle level) view, at left ventricular (LV) posterior wall. The following IBS variables were analyzed: 1) the corrected coefficient (CC) of IBS, obtained by dividing IBS intensity by IBS intensity measured in a rubber phantom, using the same equipment adjustments, at the same depth; 2) cardiac cyclic variation (CV) of IBS - peak-to-peak difference between maximal and minimal values of IBS during cardiac cycle; 3) cardiac cyclic variation index (CVI) of IBS - percentual relationship between the cyclic variation (CV) and the mean value of IBS intensity.ResultsCC of IBS was significantly larger (p < 0.05) in HYPER (1.57 ± 0.6) and HYPO (1.53 ± 0.3) as compared to SCH (1.32 ± 0.3) or N (1.15 ± 0.27). The CV (dB) (HYPO: 7.5 ± 2.4; SCH: 8.2 ± 3.1; HYPER: 8.2 ± 2.0) and the CVI (HYPO: 35.6 ± 19.7%; SCH: 34.7 ± 17.5%; HYPER: 37.8 ± 11.6%) were not significantly different in patients with thyroid dysfunction as compared to N (7.0 ± 2.0 and 44.5 ± 15.1%).ConclusionsCC of IBS was able to differentiate cardiac involvement in patients with overt HYPO and HYPER who had normal LV systolic function. These early myocardial structural abnormalities were partially reversed by drug therapy in HYPER group. On the other hand, although mean IBS intensity tended to be slightly larger in patients with SCH as compared to N, this difference was not statistical significant.

RESUMO: A Doença de Graves (DG) é a causa mais freqüente de hipertireoidismo. Sua origem é multifatorial, complexa, na qual a susceptibilidade genética interage com o meio ambiente e fatores endógenos para causar a doença. Os alelos do Complexo Principal de Histocompatibilidade (CPH) de classe II têm sido associados com a DG, em populações de diferentes etnias e muitas evidências apontam para a associação do antígeno HLA-DR3 em caucasianos. O envolvimento dos alelos do CPH na nossa população, altamente miscigenada, foi estudado em pacientes com a DG e em indivíduos-controle da mesma área geográfica, utilizando-se DNA genômico amplificado e hibridado com iniciadores de seqüência específica (SSP). O alelo HLA-DRB1*0301 esteve presente com maior freqüência (44,7%) em pacientes com DG, relativamente à população-controle (22,3%, pc=0,0068), conferindo Risco Relativo (RR) de 2,8 e uma Fração Etiológica de 28,7, enquanto o alelo HLA-DQB1*0602 esteve, significantemente, diminuído nesses pacientes (8%) em relação aos pacientes-controle (31,9%, pc=0,00062), conferindo RR de 1,8 e uma Fração Preventiva de 26,7. Apesar de a população brasileira ser altamente miscigenada, a confirmação do alelo HLA-DRB1*0301, conferindo susceptibilidade à doença, aponta esse alelo com um marcador importante na predisposição à doença. Em contraste, a proteção conferida pelo alelo HLA-DQB1*0602 parece ser peculiar aos pacientes brasileiros.