A case of thyroid hormone resistance: a rare mutation / Caso de resistência aos hormônios tireóideos: mutação rara

Reduced sensitivity to thyroid hormones (RSTH) is a rare disease that affects about 3,000 individuals, belonging to about 1,000 families. It results from reduced intracellular action of thyroid hormones (TH) genetically determined and manifests as persistent hyperthyroxinemia with non-suppressed thyroid-stimulating hormone (TSH). We describe a 67-years old, Caucasian woman, with past history of subtotal thyroidectomy due to diffuse goiter, who presents with a recurrence of goiter. Although she is clinically euthyroid, laboratory evaluation shows persistent hyperthyroxinemia with non-suppressed TSH. Response to thyrotropin releasing hormone (TRH) test was normal and TSH concentrations were not suppressed during oral administration of suprafisiologic doses of levothyroxine (L-T4). Peripheral blood DNA was extracted from the patient and a mutation was found localized in cluster one, at codon 346 of the ligand binding domain of the THRB gene. The patient’s son underwent thyroid function testing (TFT) and genetic study, both negative, suggesting a sporadic mutation. RSTH should be considered in all hyperthyroxinemic patients who are clinically euthyroid. Mutations interfering with three major steps required for TH action on target tissues have been, so far, identified (TR-β, TR-α, MCT8, SPB2). Each mutation is associated with a distinctive syndrome. Goal of management is to maintain a normal serum TSH level and a eumetabolic state and offer appropriate genetic counselling and prenatal diagnosis. Inappropriate treatment of eumetabolic patients results in hypothyroidism and need for TH replacement.

A sensibilidade reduzida aos hormônios tiroidianos (RSTH) é uma doença rara que afeta cerca de 3.000 indivíduos em 1.000 famílias. Ela resulta de uma ação intracelular reduzida de hormônios tiroidianos (TH), é geneticamente determinada e se manifesta como hipertiroxinemia persistente com hormônio tireoestimulante (TSH) não suprimido. Descrevemos o caso de uma mulher caucasiana de 67 anos de idade com histórico de tiroidectomia subtotal por bócio difuso e que apresentou recorrência do bócio. Embora ela fosse clinicamente eutiroide, a avaliação laboratorial mostrou hipertiroxinemia persistente com TSH não suprimido. A resposta ao hormônio liberador da tireotrofina (TRH) foi normal e as concentrações de TSH não foram suprimidas durante a administração oral de doses suprafisiológicas de levotiroxina (L-T4). Foi extraído DNA de sangue periférico da paciente e encontrada uma mutação no cluster um do códon 346 do domínio de ligação do ligante do gene THRB. O filho da paciente foi submetido a um teste de função da tiroide e a um estudo genético, ambos negativos, o que sugeriu uma mutação esporádica. O RSTH deve ser considerado em todos os pacientes hipertiroxinêmicos que sejam clinicamente eutiroides. Foram identificadas, até hoje, mutações que interferem com os três passos principais necessários para a ação do TH sobre os tecidos-alvo (TR-b, TR-α, MCT8, SPB2). Cada mutação está associada com uma síndrome distinta. O objetivo do manejo é manter o nível sérico normal de TSH e um estado eumetabólico, além de se oferecer aconselhamento genético adequado e diagnóstico pré-natal. O tratamento inadequado de pacientes eumetabólicos leva ao hipotireoidismo e requer reposição de TH.

A relação entre a função tireoidiana e a depressão: uma revisão / The relation between thyroid function and depression: a review

OBJETIVO: O papel da função tireoidiana nas doenças depressivas é pouco claro. Embora existam algumas evidências de que discretas alterações tireoidianas predisponham a casos de depressão, as anormalidades específicas envolvendo a tireóide e os quadros depressivos permanecem pouco conhecidas. Serão destacados nesta revisão os principais achados envolvendo os quadros depressivos e a função tireoidiana, com especial atenção na participação das monoaminas cerebrais nesta relação. MÉTODO: Foram realizados levantamento no sistema Medline e na literatura. RESULTADOS: Existem evidências de atividade alterada do eixo hipotálamo-hipófise-tireóide (HHT) em alguns casos de depressão, que incluem: aumento dos níveis de T4, resposta alterada do TSH pós-estímulo com TRH, presença de anticorpos antitireoidianos e concentração elevada de TRH no LCR. A relação entre estas anormalidades, as principais monoaminas cerebrais e os subtipos de quadros depressivos é complexa e ainda não permite o estabelecimento de hipóteses diretas de compreensão. CONCLUSÕES: Após anos de pesquisas, permanece pouco esclarecida a importância da relação entre o eixo HHT e as depressões, assim como os mecanismos subjacentes às alterações tireoidianas encontradas nos pacientes deprimidos. Portanto, mais pesquisas serão necessárias para uma melhor compreensão do papel do eixo HHT na patogênese e no tratamento dos quadros depressivos.

Correlation of expression of preprothyrotropin-releasing hormone and receptor with rat testis development / 中华医学杂志(英文版)

<p><b>OBJECTIVE</b>To investigate the expression regulation of thyrotrophin-releasing hormone (TRH) and TRH receptor (TRH-R), and their role in the development of rat testis.</p><p><b>METHODS</b>Oligonucleotide primers were designed from the sequences of rat hypothalamus prepro TRH (ppTRH) and pituitary TRH-R cDNA for reverse transcription polymerase chain reaction (RT-PCR). Specific fragments of ppTRH and TRH-R cDNA were cloned and sequenced. Expression plasmids containing ppTRH and TRH-R genes were then constructed, and expression was found in E. coli DH5-alpha. ppTRH and TRH-R mRNA in the testis was quantitated in RNA samples prepared from rats at different developmental stages by real time quantitative RT-PCR.</p><p><b>RESULTS</b>The quantitative analyses demonstrated that no ppTRH and TRH mRNA could be detected at the earliest stage (day 8). ppTRH and TRH mRNA signals were detected on day 15 and increased progressively on days 20, 35, 60 and 90.</p><p><b>CONCLUSION</b>Our results suggest that rat testis could specifically express TRH and TRH-R, and the transcriptions of ppTRH and TRH-R genes in the rat testis were development-dependent. The acquirement of expressed products for ppTRH and TRH-R can be used for further research on the physiological significance of TRH and TRH-R expression in rat testis.</p>

Thyrotropin-releasing Hormone(TRH) Receptor Gene Expression in GH3 Cells Permanently Transfected with a Mutant Gs alpha Gene / 대한내분비학회지

BACKGROUND: Gs alpha gene mutation, that constitutively increases intracellular cAMP, is found in some acromegalic patients. It was demonstrated that increased intracellular cAMP levels suppress the expression of rat TRH receptor (TRH-R) mRNA. We previously demonstrated that transient expression of a mutant Gs alpha gene suppress the rat TRH-R gene expression in the cultured rat growth hormone-secreting tumor cell line (GH3), whereas TRH-R gene expression in adenomas with Gs alpha gene mutation (gsp oncogene) did not differ from that in tumors without the mutation. The discrepancy suggests the possibilities that the effect of permanent expression of mutant Gs alpha gene on TRH-R gene expression is different from that of transient expression of the mutant gene and hypothalamic hormones including TRH regulate the gene expression. METHODS: We investigated whether permanent expression of the mutant-type Gs alpha does not suppress the TRH receptor gene expression in GH3 cells, and whether TRH suppresses the gene expression by using reverse transcription-polymerase chain reaction (RT-PCR) and in vitro transcription. RESULTS: Permanent expression of a mutant-type Gs alpha increased basal cAMP levels up to 1.7-fold relative to the controls, whereas the wild-type cell line did not show increased cAMP levels. Permanent expression of a mutant-type Gs alpha increased TRH receptor mRNA level up to 2.8 fold compared with the controls. Treatment of the permanently transfected GH3 cells with TRH suppressed TRH-R gene expression more prominently compared to the wild type GH3 cells. CONCLUSION: These results suggest that permanent expression of mutant Gs alpha enhances the expression of TRH-R in GH-secreting pituitary tumors with gsp oncogene, but the gene expression may also be regulated by other factors including TRH.

Discrepancy between in vitro and in vivo effect of Galphas gene mutation on the mRNA expression of TRH receptor

We investigated the effect of alpha-subunit of the stimulatory GTP-binding protein (Galphas) gene mutation on the expression of the thyrotropin-releasing hormone (TRH) receptor (TRH-R) gene in GH3 cells and in growth hormone (GH)-secreting adenomas of acromegalic patients. In the presence of cycloheximide, forskolin and isobutylmethylxanthine, cholera toxin, and GH-releasing hormone (GBRH) decreased rat TRH-R (rTRH-R) gene expression by about 39%, 43.7%, and 46.7%, respectively. Transient expression of a vector expressing mutant-type Galphas decreased the rTRH-R gene expression by about 50% at 24 h of transfection, whereas a wild-type Galphas expression vector did not. The transcript of human TRH-R (hTRH-R) gene was detected in 6 of 8 (75%) tumors. Three of them (50%) showed the paradoxical GH response to TRH and the other three patients did not show the response. The relative expression of hTRH-R mRNA in the tumors from patients with the paradoxical response of GH to TRH did not differ from that in the tumors from patients without the paradoxical response. Direct PCR sequencing of GALPHAs gene disclosed a mutant allele and a normal allele only at codon 201 in 4 of 8 tumors. The paradoxical response to TRH was observed in 2 of 4 patients without the mutation, and 2 of 4 patients with the mutation. The hTRH-R gene expression of pituitary adenomas did not differ between the tumors without the mutation and those with mutation. The present study suggests that the expression of TRH-R gene is not likely to be a main determinant for the paradoxical response of GH to TRH, and that Galphas mutation may suppress the gene expression of TRH-R in GH-secreting adenoma. However, a certain predisposing factor(s) may play an important role in determining the expression of TRH-R.

Avaliaçäo das funçöes tireóideas em idosos / Evaluation of the thyroid dysfunction in aged

INTRODUÇÄO: Diversos autores têm chamado a atençäo para as dificuldades no diagnóstico de disfunçäo tireóidea no idoso. Manifestaçöes características dessas afecçöes, como fadiga, pele seca, obstipaçäo, diminuiçäo da memória, humor depressivo, podem ser interpretadas como próprias do envelhecimento. OBJETIVOS: determinar a prevalência das disfunçöes tireóideas em idosos residentes em três abrigos da cidade do Salvador, avaliando as manifestaçöes clínicas no diagnóstico de disfunçöes tireóideas, a necessidade do teste de estímulo do TSH com TRH na avaliaçäo das disfunçöes tireóideas, a prevalência de anti-TPO e a associaçäo entre disfunçäo tireóidea e perfil lipídico. DESENHO DE ESTUDO: seccional. MATERIAL E MÉTODOS: foram estudados 170 idosos, voluntários, residentes em três abrigos da cidade do Salvador, com idade média de 78,4 ñ 6,8 anos, mediana de 78 anos, variando de 65 a 96 anos, sendo 27 idosos (15, 9 porcento) do sexo masculino e 143 (84,1 porcento) do sexo feminino. Nenhum deles apresentava antecedentes de doença tireoideana. Todos os idosos foram submetidos a exame clínico, as determinaçöes de T3, T4 total, T4 livre e TSH, por imunoensaios, pesquisa de anticorpos séricos anti-TPO e determinação do perfil lipídico (colesterol total e fraçöes HDL e LDL, triglicérides). Cento e vinte e dois idosos (71,8) que apresentaram TSH basal <5µUI/ml foram submetidos ao teste de estímulo com TRH (200µg), venoso, avaliado através de determinaçöes séricas de TSH nos tempos 0, 30, 60 e 90 minutos. Considerou-se hipotireoidismo franco quando o TSH (maior igual que) 5µUI/ml, com T3, T4 total e T4 livre baixos; hipotireoidismo subclínico quando o TSH (maior igual que) 5µUI/ml, com T3, T4 total e T4 livre normais ou quando o TSH após estímulo com TRH foi (maior igual que) 20µUI/ml em um dos tempos. RESULTADOS: disfunçäo tireóidea foi encontrada em 41 idosos (24, 1 porcento), sendo todos os casos representados por hipotireoidismo. Trinta idosos (17,6 porcento) apresentaram títulos significativos de anticorpos séricos anti-TPO. As manifestaçöes clínicas, nos idosos, foram atípicas, e a presença seis ou mais manifestaçöes indicou disfunçäo tireóidea. Quando se analisou as médias de CT, TG, HDL-c e LDL-c entre os idosos com e sem disfunçäo tireóidea näo houve diferença estatisticamente significante (p=0,06). Observou-se correlaçäo negativa entre níveis séricos de TSH e T3 (r = - 0,57 e p < 0,0001), T4 total (r = - 0,53 e p < 0,0001), T4 livre ...

Expression of TRH Receptor Gene in GH-Secreting Piruitary Adenomas / 대한내분비학회지

Background: To test the hypothesis that Galphas gene mutation may suppress the expression of TRH-R gene, we investigated whether hTRH-R gene expression is lower in human GH-secreting pituitary adenomas with Galphas mutation than in tumors without the mutation. Method: TRH-induced paradoxical response of GH was observed in 8 acromegalic patients. The mutation of gene was identified by direct sequencing of the genomic DNA prepared from GH-secreting pituitary adenomas. The expression of hTRHT mRNA was quantitated by RT-PCR. Results: The transcript of hTRH-R gene was detected in 6 of 8(75%) tumors. Three of these(50%) showed the paradoxical GH response to TRH and the other three patients did not show the response. The relative expression of hTRH-R mRNA in the tumors from patients with the paradoxical response of GH to TRH did not differ from that in the tumors from patients without the paradoxical response. Direct PCR sequencing of Galphas disclosed a mutant allele and a normal allele only at codon 201 in 4 of 8 tumors. The paradoxical response to TRH was observed in 2 of 4 patients without the mutation, and 2 of 4 patients with the mutation. The hTRH-R gene expression of pituitary adenomas did not differ between the tumors without the mutation and those with mutation. Conclusion: This study suggests that the expression of TRH-R gene is not likely to be a main determinant for the paradoxical response of GH to TRH, and that Galphas mutation does not seem to suppress the gene expression of TRH-R in GH secreting adenoma.

Respuestas multihormonales a una serie de pruebas neuroendocrinas en psiquiatría: una aproximación multivariada / Multihormonal responses to a series of neuroendocrine challenges in psychiatry: a multivariate approach

Mediante una batería neuroendocrina que incluye la prueba de supresión por dexamotasona, la prueba de estimulación con TRH y respuestas hormonales a apomorfina (PRL, GU, ACTH y cortisol) se estudian 86 pacientes hospitalizados, sin medicación, con los diagnósticos según DSM-IV con Depresión Mayor, esquizofrenia y trastorno esquizoafectivo y 18 controles. Se establecen las diferencias hormonales de los diversos grupos clínicos mediante el análisis factorial de correspondencia, lo que permite formular las posibles procesos fisiopatológicos subyacentes y la identificación de terapias farmacológicas apropiadas. Los resultados sugieren una disregulación cronobiológica del eje hipotálamo-hipófisis-tiroides en la depresión y una disregulación dopaminérgica en presencia de síntomas psicóticos productivos