Two abnormal thyroglobulin-like polypeptides are produced from Afrikander cattle congenital goiter mRNA

In vitro translation of the mRNA from the congenital goiter tissue of Afrikander cattle directs the synthesis of two (Mr congruent to 250,000 and congruent to 75,000, respectively) abnormal thyroglobulin-like polypeptides. Common features of these polypeptides are the following: 1) both are immunoprecipitated by purified, anti-thyroglobulin antibody; 2) the signal sequence is present on their nascent polypeptide chains, and 3) their synthesis is apparently directed by the same high molecular weight mRNA. However, the goiter thyroglobulin mRNA shows, by Northern blot analysis, a slightly reduced size (congruent to 30 S) as compared to the mRNA from normal, bovine, thyroid tissue (33 S). Furthermore, a 10- to 15-fold decrease (as assessed by dot blot hybridization) in relative mRNA concentration was observed. Thus, it can be concluded that the genetic defect in congenital goiter of Afrikander cattle results in the synthesis of an altered mRNA which is present in decreased amount and directs the synthesis of two abnormal thyroglobulin-like polypeptides.     

Radioimmunoassay for estimation of thyroglobulin in human serum.

A specific double antibody radioimmunoassay has been develop for the measurement of thyroglobulin in human serum. Human thyroglobulin was purified by combined DEAE-cellulose and affinity chromatography using Sepharose 4B-bound Concanavalin A. Sensitivity of test serum was 10 ng/ml. Thyroglobulin was not detectable in half of normal subjects, and half showed values between 10 and 180 ng/ml. In the patients with simple goiter and secondary hypothyroidism, serum thyroglobulin was usually in the normal range. In Hashimoto's thyroiditis, many sera having precipitating antibodies or high hemagglutination antibodies for thyroglobulin showed a high thyroglobulin concentration in serum probably due to a false positive reaction. In hyperthyroidism, an increased thyroglobulin level was observed in 64% of patients. However, there was no correlation between serum thyroglobulin and thyroxine levels in untreated hyperthyroidism. Serum thyroglobulin was increased significantly in some cases for several weeks after isotope therapy for the hyperthyroidism.     

H-RAS gene expression in human multinodular goiter

The RAS protooncogene has an important, although not yet established role in thyroid neoplasia. In this study, we evaluated the H-RAS mRNA and protein levels in human samples of nontoxic and toxic multinodular goiter samples, according to serum TSH levels. The mean of H-RAS mRNA levels in nodules of nontoxic nodular goiter were significantly increased compared to nonnodular tissue (1.49+/-1.21 vs. 0.94+/-0.81 AU, P=0.016). Nine of the 18 specimens (50%) of nontoxic multinodular goiter exhibited increased levels of H-RAS mRNA. The increased H-RAS mRNA levels were paralleled by inRAcreased H-Ras protein levels in about 90% of the cases. Interestingly, no differences were observed in H-RAS expression between nodules and adjacent nonnodular tissue in toxic nodular goiters (0.58+/-0.27 vs. 0.58+/-0.20 AU, P=0.88). None of the 10 samples from toxic multinodular goiters exhibited overexpression of H-RAS. The H-RAS expression was positively correlated with thyroglobulin expression (r2=0.51; P=0.04). In conclusion, we demonstrated increased levels of H-RAS mRNA and protein in samples of nontoxic multinodular goiter, indicating that it might be involved in goiter pathogenesis. In contrast, H-RAS overexpression was not detected in any of the samples of toxic multinodular goiter, suggesting different mechanisms for cell proliferation in nodular goiter according to thyroid status.     

Hormone-containing peptides from normal and goiter human thyroglobulins

A series of low iodine human thyroglobulin samples derived from colloid-rich goiter tissue was examined by HPLC mapping of tryptic digests and compared to normal human thyroglobulin. These samples ranged in iodine content from 2 to 8 gram-atoms of iodine (g.a. I) per mole and were not further iodinated in vitro. Peptides containing the principal hormonogenic sequence were detected using the long wavelength absorbance of the iodotyrosine derivatives at 325 nm. Two such peptides were isolated and sequenced. Their thyroxine content was confirmed by radioimmunoassay. The number of 325-nm-absorbing peaks was significantly lower in the normally iodinated human thyroglobulin than that observed the thyroglobulins of cattle and dog. This suggests a more restricted iodination in the human protein. Sodium dodecyl sulfate gel patterns of the reduced and alkylated proteins showed significant molecular size heterogeneity in all of the samples. Polypeptide fragments ranged in molecular size from approximately 330 to 45 kDa in the goiter derived material and from approximately 330 to 15 kDa in the normal human material. This difference between the proteins is consistent with earlier observations that peptides less than 45 kDa appear concomitantly with hormone formation. These data confirm that the human thyroglobulin molecule is capable of forming at least limited amounts of thyroid hormone at iodine levels as low as 4 g.a. I per mole. The hormone detected in this study was located at residue 5 near the amino terminus of the thyroglobulin molecule.     

Autosomal recessive inheritance of goiter in Dutch goats

The inheritance of congenital goiter due to a thyroglobulin synthesis defect in a strain of Dutch goats has been studied by Mendelian and biochemical methods. Mendelian analysis of 301 matings, resulting in 591 kids, showed an autosomal recessive mode of inheritance. A restriction fragment length polymorphism (RFLP) in the thyroglobulin gene also was used to confirm the recessive mode of inheritance of the defect. In a pedigree consisting of 27 goats, spanning four generations, the genotype determined by RFLP study was in accordance with the observed phenotype and the autosomal inheritance of the defect. Although phenotypically no differences were detected between normal and heterozygous animals, the use of RFLPs allowed the diagnosis of the three genotypes.     

Intérêt du dosage de la thyroglobulinémie chez les sujets porteurs du goitre en zones de déficience iodée au Bénin

In the present study, we analyze the results of thyroid hormones and thyroglobulinemia of 162 patients with goiter living in the departments of Collines and Donga, known to be areas of iodine deficiency in Benin. These results are compared with those of 85 healthy subjects living in the same departments. This study is a cross-sectional analytical study carried out from 1st July 2009 to 30th June 2010. The population of patients consisted of seven males and 155 females. The average age was of 45.7 years. Most of the patients were suffering of simple goiter. Only six of them had thyroid nodules. The diagnosis of biological hyperthyroidism was positive for 20 patients; 16 of them had subclinical hypothyroidism and four clinical hyperthyroidism. One case of clinical hypothyroidism was found. All other 141 patients were biologically normal (euthyroidism). Seventeen of the patients (including six patients presenting a thyroid nodule) had a normal thyroglobulin rate. Hyperthyroglobulinemia was observed in all other 145 patients. These results suggest that patients with goiter in zone of iodine deficiency are biologically euthyroid with hyper-thyroglobulinemia. Thyroglobulin dosage is then recommended, especially when nodules are perceptible.     

Application of improved coupling assay method for peroxidase of diseased thyroids: report of three cases

Recently we have developed an assay method for peroxidase-catalyzed coupling of iodotyronine residues of thyroglobulin, which is applicable to human diseased thyroid tissues. In the present study, the assay method as well as usual peroxidase assay methods were applied to thyroids of three patients (No. 1: familial goiter with impaired thyroglobulin synthesis, No. 2: mild chronic thyroiditis, No. 3: dyshormonogenetic goiter) who showed organification of iodine with high TSH levels and low thyroid hormone levels in sera. In general, these patients showed relatively high activities measured by guaiacol oxidation assay, iodide oxidation and coupling assay compared with those of control thyroids. Iodothyronine content in thyroglobulin was very low except thyroxine in No. 2. These results indicate that factors other than peroxidase may be responsible for the cause of the hypothyroid state. The coupling assay method used here is therefore useful for the detection of the 'coupling defect' in patients in a hypothyroid state.     

Myeloperoxidase-catalyzed iodination and coupling.

Myeloperoxidase (MPO), which displays considerable amino acid sequence homology with thyroid peroxidase (TPO) and lactoperoxidase (LPO), was tested for its ability to catalyze iodination of thyroglobulin and coupling of two diiodotyrosyl residues within thyroglobulin to form thyroxine. After 1 min of incubation in a system containing goiter thyroglobulin, I-, and H2O2, the pH optimum of MPO-catalyzed iodination was markedly acidic (approximately 4.0), compared to LPO (approximately 5.4) and TPO (approximately 6.6). The presence of 0.1 N Cl- or Br- shifted the pH optimum for MPO to about 5.4 but had little or no effect on TPO- or LPO-catalyzed iodination. At pH 5.4, 0.1 N Cl- and 0.1 N Br- had a marked stimulatory effect on MPO-catalyzed iodination. At pH 4.0, however, iodinating activity of MPO was almost completely inhibited by 0.1 N Cl- or Br-. Inhibition of chlorinating activity of MPO by Cl- at pH 4.0 has been previously described. When iodination of goiter thyroglobulin was performed with MPO plus the H2O2 generating system, glucose-glucose oxidase, at pH 7.0, the iodinating activity was markedly increased by 0.1 N Cl-. Under these conditions iodination and thyroxine formation were comparable to values observed with TPO. MPO and TPO were also compared for coupling activity in a system that measures coupling of diiodotyrosyl residues in thyroglobulin in the absence of iodination. MPO displayed very significant coupling activity, and, like TPO, this activity was stimulated by a low concentration of free diiodotyrosine (1 microM). The thioureylene drugs, propylthiouracil and methimazole, inhibited MPO-catalyzed iodination both reversibly and irreversibly, in a manner similar to that previously described for TPO-catalyzed iodination.     

Iodized oil as a complement to iodized salt in schoolchildren in endemic goiter in Romania

OBJECTIVE: To evaluate the long-term efficacy and possible side effects of low doses of iodized oil on iodine nutrition and thyroid function in endemic goiter in Romania. METHODS: Random selection of 214 schoolchildren aged 6-14 years. Serial measurements of urinary iodine, thyroid volume with ultrasound, serum concentrations of thyrotropin, free thyroxine, thyroglobulin and thyroid autoantibodies before and up to 2 years after the oral administration of 200 mg iodine in iodized oil. RESULTS: Urinary iodine concentrations indicated a moderate iodine deficiency before therapy, sharply increased soon after therapy and slowly decreased thereafter but remained within the normal range up to more than 1 year after therapy. The prevalence of goiter was 29% before the administration of iodized oil and 9% 1 year later. Thyroid function tests and autoantibodies were normal before and up to 2 years after therapy. CONCLUSION: A single dose of 200 mg iodine from oral Lipiodol appears adequate and safe for correcting moderate iodine deficiency in children.     

In vitro and in vivo regulation of thyrotropin receptor mRNA levels in dog and human thyroid cells.

Regulation of thyrotropin (TSH) receptor (TSHr) mRNA accumulation as compared with two other thyroid differentiation markers (thyroglobulin and thyroperoxidase (TPO] has been investigated by Northern blot. In dogs in vivo, chronic stimulation of the thyroid TSHr mRNA although it increased the levels of thyroglobulin and TPO mRNA. In dogs treated with thyroxin, the quiescent thyroids expressed normal levels of TSHr and TPO mRNA but depressed levels of thyroglobulin mRNA. In primary cultures of dog thyrocytes, dedifferentiation of the cells by treatment with epidermal growth factor or 12-O-tetradecanoylphorbol-13-acetate led to decreased TSHr mRNA levels and nearly abolished thyroglobulin and TPO gene expression. However, TSHr mRNA was always present, compatible with the fact that these cells, when treated by TSH, reexpress differentiation. Treatment of the cells with TSH or forskolin transiently increased the TSHr mRNA level after 20 h, an effect inhibited by cycloheximide. This up-regulation was confirmed at the protein level: forskolin-treated cells showed an enhanced cAMP response to TSH and an increased binding of labeled TSH to their membranes. Long term TSH treatment led to a slight down-regulation of TSHr mRNA in dog thyrocytes, but in human thyroid cells no marked down-regulation was observed.     

Mixed medullary-follicular thyroid carcinoma. Report of a case and review of the literature

OBJECTIVE: The aim was to describe the case of a female patient with a mixed medullary-follicular thyroid carcinoma. METHODS: The patient underwent thyroidectomy for the treatment of multinodular goiter. A tumor was found which exhibited the features of a mixed medullary-follicular thyroid carcinoma. Immunohistochemistry was performed. RESULTS: Immunohistochemistry was positive in the area of the carcinoma for calcitonin and thyroglobulin. She developed extensive metastatic deposits in the bones of the pelvis and in the calvarium causing hyperthyroidism. CONCLUSION: A patient with a mixed medullary-follicular thyroid carcinoma is described, who had elevated levels of both calcitonin and thyroglobulin and developed metastatic deposits, which could produce thyroid hormones.     

Reverse transcription of thyroglobulin 33-S mRNA.

Bovine thyroglobulin 33-S mRNA has been used as a template for the synthesis of a complementary DNA, using RNA-directed DNA polymerase from the avian myeloblastosis virus. The yield of the reaction was relatively poor and the size of the cDNA did not exceed 10 S. Nevertheless, a copy of high specific radioactivity (approximately 10(7) counts. min-1 microgram-1) could be obtained which hybridized specifically back to its template with an rot1/2 value about 5 times higher than that observed in hybridizations between hemoglobin mRNA (alpha + beta chain) and hemoglobin cDNA. This suggests that thyroglobulin mRNA does not contain extensive internal repetitive sequences. Quantification of thyroglobulin mRNA sequences among various RNA preparations from the beef thyroid was performed using cDNA/RNA hybridizations in RNA excess. The results confirmed that thyroglobulin mRNA represents the large majority of mRNA in membrane-bound polysomes and indicated the virtual absence of thyroglobulin sequences on free polyosomes. The cDNA transcribed from mRNA of bovine origin hybridized efficiently with thyroid RNA from goats, dogs and humans. Although the heterologuous hybrids exhibited the expected decrease in thermal stability, the bovine cDNA provides an appropriate probe for studies dealing with the expression of the thyroglobulin gene in various mammals including man.     

Antagonistic effects of thyrotropin and epidermal growth factor on thyroglobulin mRNA level in cultured thyroid cells

Both thyrotropin (TSH) and epidermal growth factor (EGF) are potent mitogenic agents when added to dog thyroid cells in primary culture [Roger, P. P. and Dumont, J. E. (1984) Mol. Cell. Endocrinol. 36, 79-93]. The concomitant effect of these agents on the differentiation state of the cells was appreciated using cell morphology, iodide trapping, thyroglobulin synthesis and cytoplasmic thyroglobulin mRNA content as markers. Together with previous results [Mol. Cell. Endocrinol. 36, 79-93 (1984)] it is shown that cells cultured in the continuous presence of TSH maintain all the parameters at a near normal level. In the absence of TSH, thyroglobulin mRNA decreased to very low, though still detectable levels. Addition of TSH restored subnormal mRNA levels. Culture of cells in the presence of EGF for 4-6 days affected profoundly their morphology, abolished iodide trapping and decreased thyroglobulin synthesis and cytoplasmic mRNA content to undetectable levels. Addition of TSH to cells previously exposed to EGF reversed the growth factor effect on all four indexes. The redifferentiating effect of TSH was well observed within 3-4 days and was mimicked by the adenylate cyclase activators, forskolin and cholera toxin. When administered simultaneously, TSH and EGF achieved an intermediate situation, EGF antagonizing partially the effect of TSH on the expression of thyroglobulin gene. Another growth factor, fibroblast growth factor, while promoting thyroid cell proliferation also, did not interfere at all with TSH effects on cytoplasmic thyroglobulin mRNA content. Our results make the dog thyroid cell in primary culture an appropriate model to study the mechanisms involved in gene regulation by cyclic AMP and growth factors.     

Demonstration of a heterogeneous transcription pattern of thyroglobulin mRNA in human thyroid tissues.

Previous reports on human thyroglobulin (hTg) modifications in thyroid carcinomas prompted us to study hTg mRNA in thyroid adenomas and carcinomas. The quantification of hTg mRNA showed a decrease in its levels of expression in both pathological conditions which differed by a factor of 2 between adenomas and carcinomas. Furthermore, PCR was used to analyse the characteristics of hTg mRNA by amplifying 4 regions of the hTg mRNA. When applied to 2 normal, 17 benign and 13 malignant pathological tissue specimens, PCR showed no modification in the size of Tg mRNA. However, abnormal sized cDNAs appeared in all tissues with no distinction between the pathologies; the Restriction Fragment Length Polymorphism study of these cDNAs suggests the existence of alternate splicing patterns in thyroglobulin mRNAs.     

A simple semiquantitative radiometric measurement of antithyroglobulin antibodies in human serum. Comparison with hemagglutination method

A simple solid-phase radiometric assay for the measurement of thyroglobulin autoantibodies (TgRA) was developed and evaluated. The assay is semiquantitative, and the results were expressed as a ratio between sample versus negative control (normal human serum). In 59 normal subjects, the mean ratio was 0.93 +/- (SD) 0.34. Thyroglobulin antibodies by radiometric assay, by hemagglutination (TgHA), as well as microsomal antibodies by hemagglutination (MCHA) were measured in 41 patients with a histopathologic diagnosis of Hashimoto's thyroiditis (n = 22), adenomatous goiter (n = 10), carcinoma (n = 5), adenoma (n = 4), and in 59 patients without histopathologic diagnosis of thyroid disease. In patients with Hashimoto's thyroiditis, TgRA, TgHA, and MCHA were positive in 54, 31, and 81% of patients, respectively. 1 patient had positive TgRA with negative MCHA levels, and 2 had negative antibody titers by all methods. Thyrotropin-stimulating hormone levels were elevated (greater than 10 microU/ml) in 17 of these patients. Our results suggest that although the TgRA method is more sensitive than TgHA for detecting thyroglobulin antibodies, its diagnostic sensitivity is not equal to that of MCHA.     

Messenger RNA properties of primary cultures of thyroid cells isolated from normal thyroid tissue and from patients with various thyroid diseases.

When compared to cells isolated from normal thyroid tissue, cells isolated from colloid adenoma have the same total polyadenylic acid content and total template activity. However, in both the cells isolated from diffuse non toxic goiter and from toxic adenoma, these two values are increased, the most striking effect being observed in the latter case. Moreover, as compared to normal thyroid tissue, in the three thyroid diseases and particularly in toxic adenoma, we observed an increase in the polyadenylic acid and messenger activity associated to RNA sedimenting at greater than 30 S, which correspond probably to thyroglobulin messenger RNA.     

Characterization of the two oligosaccharides present in the preferential hormonogenic domain of human thyroglobulin

The N-terminal fragment of human thyroglobulin (residues 1 to 171) contains the preferential hormonogenic site of the molecule and 2 potential sites of N-glycosylation (Asn57 and Asn91). This fragment was isolated from a human thyroglobulin purified from a single goiter. The tryptic peptides bearing the glycosylation sites were separated by Bio-Gel P-30 and HPLC columns. The oligosaccharides borne at each site were analyzed, after tritium labeling, by concanavalin A-Sepharose and HPLC. At both sites the structures observed are heterogenous, with a majority of biantennary complex type structures.