Cases reported "Goiter"

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1/7. A premature stopcodon in thyroglobulin messenger rna results in familial goiter and moderate hypothyroidism.

    Impaired thyroglobulin (Tg) synthesis is one of the putative causes for dyshormonogenesis of the thyroid gland. This type of hypothyroidism is characterized by intact iodide trapping, normal organification of iodide, and usually low serum Tg levels in relation to high TSH, and when untreated the patients develop goiter. In thyroid tissue from a 13-yr-old patient suspected of a thyroglobulin synthesis defect, the Tg mRNA was studied. The complete coding region of 8307 bp was directly sequenced and revealed a homozygous point mutation: a C886T transition in exon 7. Upon translation this mutation would result in a stopcodon at amino acid position 277, replacing the arginine residue. A Tg cDNA construct containing the mutation was expressed in rabbit reticulocyte lysate resulting in a truncated protein of 30 kDa. Expression in the presence of microsomal membranes resulted in a gel shift of this Tg molecule, indicating glycosylation ability. Two other siblings had a clinical presentation like the index patient, while their parents were unaffected. Additional restriction fragment length polymorphism analysis of the pedigree verified that the homozygous nonsense mutation cosegregated with the clinical phenotype. Clinically, hypothyroidism was not severe in the affected siblings because the truncated Tg glycoprotein was still capable of thyroid hormonogenesis.
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2/7. Differential levels of thyroid peroxidase and thyroglobulin messenger ribonucleic acids in congenital goiter with defective thyroglobulin synthesis.

    The biosynthesis of thyroid hormones requires iodide, thyroid peroxidase (TPO), thyroglobulin (Tg) and H2O2. We have studied two sisters with congenital large goiters and hypothyroidism. Perchlorate tests were negative. serum T3 and T4 were decreased, TSH was increased and Tg was within the lower limit of normal. Biochemical and molecular studies were performed on goiter samples obtained after surgery. Tg content in both tissues was negligible. paper chromatography of labeled iodocompounds showed a decrease in T4, and the presence of a pronase/pancreatin-resistant iodoprotein. TPO activity was normal in the tissues. Sephacryl S-300 gel filtration demonstrated labeled iodoalbumin-like protein and the absence of a Tg peak. Salting out studies of soluble protein fraction gave an abnormal pattern. Agarose gel electrophoresis showed the presence of an iodoalbumin-like protein and the absence of Tg in the tissues. This last finding was confirmed by immunoelectrophoresis. The Tg and TPO mRNAs levels were also analyzed. Dot-blot hybridization studies with pM5 (TPO cDNA) and phTgM2 (Tg cDNA) probes showed increased and decreased signals, respectively. The increase in TPO mRNA can be explained as a compensatory mechanism vis a vis an increase in serum TSH caused by decreased serum T3 and T4 due to the impairment in Tg mRNA. The Tg mRNA of both patients was further studied with four different probes covering 5' and 3' regions (phTgM1, phTgB1, phTgB2 and phTgB3). Hybridization was observed with all four probes, thus excluding a dramatic deletion defect. Northern transfer showed a clear signal of hybridization with the phTgB1 probe in the 8-9 Kb range. We may conclude that the biochemical and molecular abnormality of these patients is characterized by a decrease of Tg mRNA and of Tg translation.
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3/7. Low levels of thyroglobulin messenger ribonucleic acid in congenital goitrous hypothyroidism with defective thyroglobulin synthesis.

    We characterized the virtual absence of immunoassayable thyroglobulin (Tg) in the serum and thyroid gland of two siblings (MA, JNA) and one nephew (RSS) from a family without inbreeding or familial goiter. diagnosis of defective Tg gene expression was based on findings of normal PBI and low serum T4, low or normal serum T3, negative perchlorate discharge test, and virtual absence of the serum Tg response to challenge by bovine TSH. This conclusion was confirmed by analysis of proteins in the goiter extracts. Only minute amounts of immunoassayable Tg were detected by RIA (MA, 0.11; JNA, 0.19 mg/g tissue; compared to 70-90 mg/g in normal thyroid tissue). Gel filtration in Sephacryl S300 showed the absence of a normal Tg peak at 280 nm and concentration of label mostly on albumin. A minor intermediate peak of radioactivity was also detected, with the size of, approximately, normal Tg. sodium dodecyl sulfate-agarose gel electrophoresis indicated the absence of Tg dimer and monomer, and Western blotting and immunoelectrophoresis confirmed this finding. Dot blot quantification of Tg and thyroid peroxidase mRNA indicated decreased hybridization of the patients' mRNA (MA, 44%; JNA, 63%) with phTgM2 (Tg probe) and increased hybridization (MA, 191%; JNA, 182%) with the pM5 (thyroid peroxidase probe) compared with control thyroid tissue. Dot blot analysis of Tg mRNA from the two siblings weakly hybridized with 3' and 5' Tg probes. rna analysis by means of Northern transfer showed a clear signal of hybridization with Tg probe (phTgM1) in the 8- to 9-kilobase range, corresponding to the normal size Tg mRNA. No major polymorphisms were noted in Southern blotting, using seven restriction endonucleases. We conclude that no gross alteration of the 5' region of Tg gene was present in these patients. Ultrastructural examination of the thyroid tissue indicated that the rough endoplasmic reticulum was not augmented, nor were the cisternae of rough endoplasmic reticulum dilated. The defect observed in these goiters is diminished tissue concentration of Tg mRNA with defective translation. However, small amounts of functionally active Tg could be synthesized, iodinated, and immediately hydrolized, yielding mostly T3, owing to the intense tissue stimulation by TSH.
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4/7. Normal level of thyroglobulin messenger ribonucleic acid in a human congenital goiter with thyroglobulin deficiency.

    Two siblings with congenital goiter were investigated from clinical, biochemical, and molecular biology standpoints. The association of clinical and biological hypothyroidism with undetectable levels of serum thyroglobulin (Tg) and the presence of iodohistidines in the urine suggested the diagnosis of defective Tg gene expression. This conclusion was confirmed by analysis of proteins present in goiter extracts. Only minute amounts of Tg-related material was detected by RIA (0.28 and 0.17 mg/g tissue compared to 80-100 mg/g in normal thyroid tissue), by sepharose 6B chromatography, and by sucrose density gradient centrifugation. Surprisingly, the goiters contained normal amounts of Tg mRNA. The size of the mRNA and the sequence organization of its first five exons also were normal. We conclude that no gross alteration of structure or transcription of the Tg gene was present in these patients. The results are compatible with a lesion affecting the mRNA sequence (point mutation, splicing error etc.), leading to defective translation or abnormal routing of the translation product through the membrane system of the cell. This latter hypothesis is supported by the extreme distension of the goiter endoplasmic reticulum found on electron microscopy.
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5/7. A 138-nucleotide deletion in the thyroglobulin ribonucleic acid messenger in a congenital goiter with defective thyroglobulin synthesis.

    Two siblings (HSN and AcSN) with congenital goitrous hypothyroidism were investigated in terms of clinical, biochemical, and molecular biology. diagnosis of defective thyroglobulin (Tg) was based on findings of low serum T4, low normal or normal serum T3, a negative percholate discharge test, and the virtual absence of the serum Tg response to challenge by bovine TSH. Only minute amounts of Tg-related antigens were detected by RIA in the goitrous tissue (HSN, 0.82 mg/g, compared to 70-90 mg/g in normal thyroid tissue), as confirmed by sodium dodecyl sulfate-agarose gel electrophoresis that indicated the virtual absence of Tg. The Tg messenger ribonucleic acids (mRNAs) from controls and HSN thyroid tissue were first reverse transcribed and then divided into several portions from positions 57-8448; the resulting complementary DNAs were, in turn, amplified by reverse polymerase chain reaction. The amplification of nucleotides 5165-6048 from control thyroid tissue Tg mRNA showed a fragment of 884 base pairs (bp). In contrast, the fragment present in the HSN was /- 750 bp and lacked the normal fragment. The sequencing of the smaller fragment revealed that 138 bp were missing between positions 5590-5727 of the HSN Tg mRNA. This deletion does not affect the reading frame of the resulting mRNA and is potentially fully translatable into a Tg polypeptide chain that is shorter by 46 residues. A cysteine residue is maintained by the junction between the proximal T from leucine 1831 and the distal GT from cysteine 1877. dna genomic polymerase chain reaction amplification excludes a deletion in the Tg gene and indicates that the deleted 138-nucleotide sequences lie in the same exon. The functional consequences of the deletion are not entirely clear, but it is conceivable that the excision of this segment of the Tg molecule could affect the protein structure, resulting in its premature degradation, very low colloid storage, and diminished thyroid hormone production rate.
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6/7. Thyroids from siblings with Pendred's syndrome contain thyroglobulin messenger ribonucleic acid variants.

    We studied thyroid tissue from two siblings with Pendred's syndrome (familial goiter and congenital deafness), both with the Mondini-type inner ear malformation, goiter, and hypothyroidism. iodine trapping and peroxidase levels were grossly normal. thyroglobulin (Tg), the only iodoprotein found, had a normal monomer size (330 kilodaltons), but low content of hormone and iodine. Tg's expected N-terminal peptides of 26 and 18 kilodaltons, usually formed in association with iodination and thyroid hormone synthesis, were absent, but appeared after iodination in vitro. reverse transcription of ribonucleic acid from Pendred thyroid tissue and amplification by polymerase chain reaction of specific regions encoding the most important hormonogenic sites of Tg revealed a normal complementary dna sequence corresponding to the first 100 amino acid residues in Tg's N-terminus. However, 3 of 35 clones of the 3'-region corresponding to the Tg C-terminus exhibited a deletion of nucleotides 7860-7994; this deletion was not present in any of the 150 clones from 7 other thyroids we examined. Four Pendred clones had a 2-nucleotide deletion at positions 7870-7871, a change that would result in a premature stop codon and was found in thyroids from several other subjects as well. We conclude that the messenger ribonucleic acid encoding the 3'-region of Tg can be abnormal in Pendred's syndrome. Some, but not all, of these changes also occur in other human thyroids. Further work is necessary to show if and how these alterations relate to defective hormone synthesis and goiter.
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7/7. Defective organification of iodide causing congenital goitrous hypothyroidism.

    A 26-yr-old Japanese woman with congenital goitrous hypo-thyroidism and sensorineural deafness underwent a thyroidectomy. Examination of the thyroid gland revealed characteristic features of multinodular goiter. The T3 and T4 content in thyroglobulin (Tg) were 0.03 and 0.02 mol/mol Tg, respectively. Iodide incorporation into Tg, using slices of the thyroid tissue, revealed that iodide organification of thyroid tissue from our patient was markedly lower than that of normal controls. Then, guaiacol and iodide oxidation activities of thyroid peroxidase (TPO) in our patient's thyroid tissue were lower than those of normal controls (guaiacol assay: 1.92 vs. 30.0 /- 5.7 mGU/mg protein; iodide assay: 1.1 vs. 6.6 /- 2.8 mIU/mg protein). Lineweaver-Burk plot analysis of the oxidation rates of guaiacol and iodide indicated that this patient's TPO had a defect in the binding of guaiacol and iodide, but the coupling activity of the patient's TPO was not decreased compared with those of two normal thyroids. In this case and in control subjects, Nothern gel analysis of TPO messenger rna from unstimulated and TSH-stimulated thyroid cells revealed a 3.2 kilobase species in the former and four distinct messenger rna species of 4.0, 3.2, 2.1, and 1.7 kilobases in the latter. Western blot analysis of TPOs obtained from this patient and from control subjects identified the same 107 kDa protein, using antimicrosomal antibody-positive serum. We analyzed the coding sequence in the patient's TPO gene by using polymerase chain reaction technique. A single point mutation of G-->C at 1265 base pair was detected only in the TPO gene, but this point mutation does not alter the amino acid residue. It is possible that posttranslational modification such as abnormal glycosylation may occur in the TPO molecules. Furthermore, it is possible that there are differences in the tertiary structures of the TPO molecules between our patient and normal subjects. The above abnormalities of TPO molecules may play an important role in our patient's dyshormonogenesis.
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