The epizootiology and pathogenesis of thyroid hyperplasia in coho salmon (Oncorhynchus kisutch) in Lake Ontario.
The thyroid glands of coho salmon collected at different stages of their anadromous migration exhibited progressive and extensive hyperplasia and hypertrophy. The incidence of overt nodule formation rose from 5% in fish collected in August to 24% in fish collected in October. The histological picture of the goiters was similar to that found in thiourea-treated teleosts and thiouracil-treated mammals. There was a concomitant, significant decrease in serum thyroxine and triiodothyronine values between September and October (thyroxine, 1.0+/-0.3 mug/100 ml and 0.4 mug/100 ml in September and October, respectively; triiodothyronine, 400.3+/-51.6 ng/100 ml and 80.2 ng/100 ml in September and October, respectively) and marked hypertrophy and hyperplasia of thyrotrophs. These data indicate a progressive hypothyroid condition which, although it may be linked to iodide deficiency, may well be enhanced by other environmental factors. The evidence for involvement of other factors is discussed. (+info)
Maximal number of hormonogenic iodotyrosine residues in thyroglobulin iodinated by thyroid peroxidase.
Almost non-iodinated human goiter thyroglobulin has been iodinated in vitro by thyroid peroxidase to levels as high as 75 iodine atoms per mol of protein. The following results were obtained. 1. The iodine distribution obtained in vitro with human thyroglobulin strongly ressembles that obtained in vivo for rat thyroglobulin. Thus the distribution of iodine seems to depend essentially on the structure of thyroglobulin and on the reactivity of the different tyrosine residues. 2. Although the number of hormone residues increased with iodination the highest efficiency of hormone synthesis was obtained in a very narrow range of iodination: in vitro (40%) between 25 and 30 iodine atoms, and in vivo (48%) between 10 and 20 atoms. This result suggests that the tyrosines which are coupled with a high efficiency are iodinated sequentially. 3. Maximal thyroxine content was found to be lower than approximately 3 mol/mol of thyroglobulin. This result might mean that the two 12-S subunits of thyroglobulin are not identical and that one of them is able to produce 2 mol of hormone while the second only 1 mol. (+info)
Kinetics of thyroglobulin iodination and of hormone synthesis catalysed by thyroid peroxidase. Role of iodide in the coupling reaction.
The kinetics of tyrosine iodination and of thyroxine synthesis in thyroglobulin, different reactions catalyzed by the same enzyme (thyroid peroxidase), have been compared. Thyroxine synthesis always began after a lag period of 3-5 min. This lag was constant whatever the rate of iodination; this rate of iodination was increased either by increasing the concentration of iodide or enzyme or by decreasing the concentration of thyroglobulin. Increasing the rate of iodination resulted in increasing the number of iodine atoms incorporated during the lag period. Thus the lag observed for thyroxine synthesis was constant and did not depend on the fact that free iodide or non-iodinated tyrosine residues of thyroglobulin were exhausted before thyroxine synthesis occurred. Finally, it appeared that, whatever the explanation of the lag, the enzyme catlyzes thyroid hormone synthesis at a slower rate than iodination. The existence of a lag also allowed us to prepare thyroglobulin samples with different iodine contents but without thyroid hormones. Thus iodination and thyroxine synthesis could be studied independently and the following results were obtained. 1. Iodotyrosine residues which can couple to form thytoxine are made considerably before coupling occurs. 2. H2O2 is required for coupling of these hormonogenic residues; thus the coupling reaction requires enzymic oxidation of the iodotyrosine residues. 3. In addition a strict requirement for iodide was needed for coupling; the requirement was dependent on the concentration of iodide. Thus iodide, a substrate of the iodination reaction, may also have other effects on the activity of thyroid peroxidase. (+info)
Large goitre causing difficult intubation and failure to intubate using the intubating laryngeal mask airway: lessons for next time.
A 63-yr-old woman was anaesthetized for sub-total thyroidectomy. The thyroid gland was large, deviating the trachea to the right and causing 30% tracheal narrowing at the level of the suprasternal notch. Mask ventilation was easy but laryngoscopy was Cormack and Lehane grade 3. Despite being able to see the tip of the epiglottis, tracheal intubation was impossible. An intubating laryngeal mask was inserted and although the airway was clear and ventilation easy, it was not possible to intubate the trachea either blindly or with the fibreoptic bronchoscope. Tracheal intubation was eventually achieved using a 6.5-mm cuffed oral tracheal tube via a size 4 laryngeal mask under fibreoptic control. We describe the case in detail and discuss the use of the intubating laryngeal mask, its potential limitations and how to optimize its use in similar circumstances. (+info)
Local versus WHO/International Council for Control of Iodine Deficiency Disorders-recommended thyroid volume reference in the assessment of iodine deficiency disorders.
OBJECTIVE: Iodine deficiency endemia is defined by the goitre prevalence and the median urinary iodine concentration in a population. Lack of local thyroid volume reference data may bring many health workers to use the European-based WHO/International Council for Control of Iodine Deficiency Disorders (ICCIDD)-recommended reference for the assessment of goitre prevalence in children in different developing countries. The present study was conducted in non-iodine-deficient areas in Malaysia to obtain local children's normative thyroid volume reference data, and to compare their usefulness with those of the WHO/ICCIDD-recommended reference for the assessment of iodine-deficiency disorders (IDD) in Malaysia. DESIGN AND METHODS: Cross-sectional thyroid ultrasonographic data of 7410 school children (4004 boys, 3406 girls), aged 7-10 years, from non-iodine-deficient areas (urban and rural) in Peninsular Malaysia were collected. Age/sex- and body surface area/sex-specific upper limits (97th percentile) of normal thyroid volume were derived. Thyroid ultrasonographic data of similar-age children from schools located in a mildly iodine-deficient area, a severely iodine-deficient area, and a non-iodine-deficient area were also collected; spot urines were obtained from these children for iodine determination. RESULTS: The goitre prevalences obtained using the local reference were consistent with the median urinary iodine concentrations in indicating the severity of IDD in the areas studied. In contrast, the results obtained using the WHO/ICCIDD-recommended reference showed lack of congruency with the median urinary iodine concentrations, and grossly underestimated the problem. The local sex-specific reference values at different ages and body surface areas are not a constant proportion of the WHO/ICCIDD-recommended reference. A further limitation of the WHO/ICCIDD-recommended reference is the lack of normative values for children with small body surface areas (<0.8m2) commonly found in the developing countries. CONCLUSION: The observations favour the use of a local reference in the screening of children for thyroid enlargement. (+info)
Thyroid volumes in US and Bangladeshi schoolchildren: comparison with European schoolchildren.
OBJECTIVE: The World Health Organization (WHO) recently adopted thyroid volume ultrasonography results from European schoolchildren as the international reference for assessing iodine deficiency disorders. Our objective was to describe thyroid volumes measured by ultrasonography in US and Bangladeshi schoolchildren and compare these with European schoolchildren. METHODS: Cross-sectional studies were performed in schoolchildren in the US (n=302) and Bangladesh (n=398). Data were collected on the following: thyroid size by palpation and ultrasonography; urinary iodine; age; sex; weight; and height. RESULTS: Applying the new WHO thyroid volume references to the Bangladeshi children resulted in prevalence estimates of enlarged thyroid of 26% based on body surface area (BSA) and 7% based on age. In contrast, in the US children, the prevalence estimates were less than 1% for each reference. In the US children, the best single predictor of thyroid volume was BSA (R2=0.32), followed by weight (R2=0.31). Using linear regression, upper normal limits (97th percentile) of thyroid volume from US children were calculated for BSA, weight and age, and were found to be lower than the corresponding references based on BSA and age from European schoolchildren. CONCLUSIONS: In areas with malnutrition, such as Bangladesh, the BSA reference should be preferred to the reference based on age. Results from the US children indicated that a thyroid volume reference based on weight alone would perform as well as the one based on BSA. European schoolchildren had larger thyroids than US children, perhaps due to a residual effect of iodine deficiency in the recent past in some areas in Europe. (+info)
Regulation of thymosin beta10 expression by TSH and other mitogenic signals in the thyroid gland and in cultured thyrocytes.
OBJECTIVE: To investigate the expression of thymosin beta10 - a small conserved acidic protein involved in the inhibition of actin polymerization - in human and experimental thyroid goiters as well as the regulation exerted by TSH on thymosin beta10 expression in thyroid follicular cells both in vivo and in vitro. DESIGN: To this aim, we have used 5 bioptic specimens from patients affected by thyroid goiter, a well known experimental model of thyroid goitrogenesis (rat fed with the drug propylthiouracil) and a cultured rat thyroid cell line (PC Cl 3 cells) as a model system. RESULTS: We report that the mRNA expression of thymosin beta10 is markedly enhanced in human goiters compared with normal thyroid. In vivo results showed that the steady-state level of thymosin beta10 mRNA is up-regulated in the thyroid gland of propylthiouracil-fed rats in parallel with follicular cell proliferation: iodide administration to goitrous rats, which induced a marked involution of thyroid hyperplasia, reduced the mRNA level of thymosin beta10. Finally, in vitro studies showed that in cultured rat thyrocytes, the expression of thymosin beta10 mRNA is induced in a time- and dose-dependent manner by the activation of pathways which are mitogenic for thyroid cells (i.e. the protein kinase (PK) A and PKC pathways). CONCLUSION: Taken together, the findings reported here demonstrate that thymosin beta10 expression is regulated by extracellular signals that stimulate growth of thyroid cells both in vitro and in vivo, and suggest a role for this protein in thyroid diseases characterized by proliferation of follicular cells. (+info)
A case of Graves' disease associated with autoimmune hepatitis and mixed connective tissue disease.
The patient was a woman of forty-eight. Liver dysfunction was pointed out at the age of forty-five. She was admitted to hospital because of her hyperthyroidism. Her palmar skin was wet and her fingers were swollen like sausages. She had a diffuse and elastic hard goiter with a rough surface. The serum levels of free T3 (9.6 pg/mL) and free T4 (3.76 ng/dL) were high and that of TSH (0.11 microU/mL) was low. The activity of TSH-binding inhibitory immunoglobulin (TBII) was 89%. The uptake rate of 123I to the thyroid was 55.1% and the uptake pattern was nearly diffuse. The goiter was proved to contain several nodules by ultrasonography, but aspiration cytology showed no malignant cells. She was diagnosed to have Graves' disease with adenomatous goiter. She also had high ALT (34 IU/L) and gamma-globulin (1.97 g/dL). She had positive antinuclear antibody (speckled type), positive anti-ribosomal nuclear protein antibody, and positive LE cell phenomenon. The liver biopsy revealed mononuclear cell infiltration with fibrosis in the portal area. These data indicated that she also had autoimmune hepatitis (AIH) and mixed connective tissue disease (MCTD). The analysis of human leukocyte antigen (HLA) showed positive A11 which had been reported to relate to Graves' disease, and positive DR4 which had been reported to relate to AIH and MCTD. These results suggested that HLA would determine susceptibility to three distinct autoimmune diseases in this case. (+info)