Increased frequency of euthyroid ophthalmopathy in patients with Graves' disease associated with myasthenia gravis

We previously showed that myasthenia gravis (MG) has a mild clinical expression when associated with autoimmune thyroid diseases (AITD). In the present study we have investigated the frequency of thyroid-associated ophthalmopathy (TAO) in patients with Graves' disease (GD) associated with MG as compared with GD patients without MG. A total of 418 patients with GD were studied, 31 with MG and 387 without MG. TAO was evaluated by physical examination, exophthalmometry, computerized tomography, and computerized visual fields assessment. The overall prevalence of TAO was similar in GD patients with MG (61.2%) and in those without MG (56.4%). When the analysis was restricted to GD patients with ocular MG, a greater frequency of TAO was found (84.6%), compared with GD patients without MG or with GD patients with generalized MG, although the differences did not reach the statistical significance. GD patients with MG had a significantly greater prevalence (12.9%) of euthyroid ophthalmopathy (clinically overt ophthalmopathy without previous and/or current hyperthyroidism) than those without MG (3.1%; p = 0.003). The results suggest a preferential association between the ocular manifestations of GD and MG, which may be due to immunological cross-reactivity against common autoimmune targets in the eye muscle as well as to a common genetic background.

The effect of short-term low-dose perchlorate on various aspects of thyroid function

Perchlorate (ClO4) salts are found in rocket fuel, fireworks, and fertilizer. Because of ground water contamination, ClO4 has recently been detected in large public water supplies in several states in the 4-18 microg/L (parts per billion [ppb]) range. The potential adverse effect of chronic low level ClO4 ingestion on thyroid function is of concern to the Environmental Protection Agency (EPA). The daily ingestion of ClO4 at these levels would be magnitudes below the therapeutic effect level of hundreds of milligrams of ClO4 used in treating hyperthyroidism. Studies were carried out in nine healthy male volunteers who had normal thyroid function and negative thyroid antibodies to determine whether the ingestion of 10 mg of ClO4 daily (approximately 300 times the estimated maximum amount of ClO4 consumed from the affected water supplies) would affect any aspect of thyroid function. They ingested 10 mg of ClO4 dissolved in a liter of spring water during waking hours for 14 days. Baseline serum thyrotropin (TSH), free thyroxine index (FTI), total triiodothyronine (TT3), 4-, 8-, and 24-hour thyroid 123I uptakes (RAIU), serum and 24-hour urine ClO4, 24-hour urine iodine, complete blood count (CBC), and chemistry profile were determined. All blood and urine tests were repeated on days 7 and 14 of ClO4 administration and thyroid RAIU on day 14 of ClO4 administration. All tests were repeated 14 days after ClO4 was discontinued. No effect of ClO4 on serum thyroid hormone or TSH concentrations, urinary iodine excretion, CBC, or blood chemistry was observed. Urine and serum ClO4 levels were appropriately elevated during the course of ClO4 ingestion in all subjects, demonstrating compliance. By day 14 of ClO4 administration, the 4-, 8-, and 24-hour thyroid RAIU values decreased in all nine subjects by a mean value of 38% from baseline and rebounded above baseline values by 25% at 14 days after ClO4 withdrawal (p < 0.01 analysis of variance (ANOVA) and Tukey). It is well known that the major effect of ClO4 on the thyroid is a decrease in the thyroid iodide trap by competitive inhibition of the sodium iodide symporter (NIS). The present study demonstrates the sensitivity of the thyroid iodide trap to ClO4 because a low dose of 10 mg daily significantly decreased the thyroid RAIU without affecting circulating thyroid hormone or TSH concentrations. It is possible, however, that the daily consumption of low levels of ClO4 in drinking water over a prolonged period of time could adversely affect thyroid function but no evidence of hypothyroidism was observed at 10 mg of ClO4 daily in this 2-week study. It is now of interest to determine a no effect level for ClO4 on the inhibition of the thyroid RAIU and to carry out a long-term ClO4 exposure study.

A comparison of recombinant human thyrotropin and thyroid hormone withdrawal for the detection of thyroid remnant or cancer

Recombinant human TSH has been developed to facilitate monitoring for thyroid carcinoma recurrence or persistence without the attendant morbidity of hypothyroidism seen after thyroid hormone withdrawal. The objectives of this study were to compare the effect of administered recombinant human TSH with thyroid hormone withdrawal on the results of radioiodine whole body scanning (WBS) and serum thyroglobulin (Tg) levels. Two hundred and twenty-nine adult patients with differentiated thyroid cancer requiring radioiodine WBS were studied. Radioiodine WBS and serum Tg measurements were performed after administration of recombinant human TSH and again after thyroid hormone withdrawal in each patient. Radioiodine whole body scans were concordant between the recombinant TSH-stimulated and thyroid hormone withdrawal phases in 195 of 220 (89%) patients. Of the discordant scans, 8 (4%) had superior scans after recombinant human TSH administration, and 17 (8%) had superior scans after thyroid hormone withdrawal (P = 0.108). Based on a serum Tg level of 2 ng/mL or more, thyroid tissue or cancer was detected during thyroid hormone therapy in 22%, after recombinant human TSH stimulation in 52%, and after thyroid hormone withdrawal in 56% of patients with disease or tissue limited to the thyroid bed and in 80%, 100%, and 100% of patients, respectively, with metastatic disease. A combination of radioiodine WBS and serum Tg after recombinant human TSH stimulation detected thyroid tissue or cancer in 93% of patients with disease or tissue limited to the thyroid bed and 100% of patients with metastatic disease. In conclusion, recombinant human TSH administration is a safe and effective means of stimulating radioiodine uptake and serum Tg levels in patients undergoing evaluation for thyroid cancer persistence and recurrence.

Fas and Fas ligand gene expression in autoimmune thyroiditis in BB/W rats

OBJECTIVE

Apoptosis via the Fas pathway is a potential mechanism for thyroid tissue destruction leading to clinical hypothyroidism in Hashimoto's thyroiditis (HT). Recent studies reported contradictory results regarding the regulation of Fas/Fas ligand (FasL) expression by cytokines in vitro. We therefore determined the Fas and FasL gene expression in the BioBreeding/Worcester (BB/W) rat thyroiditis model, which can be regarded as a model for HT.

METHODS

In order to obtain BB/W rats with spontaneous, iodine-induced or without lymphocytic thyroiditis (LT), rats were divided into 3 groups: 55-day-old rats after 24 days of iodine administration, 75-day-old rats after 45 days of iodine administration, and 101-day-old rats respectively. The gene expression of Fas, FasL, and interleukin (IL)-1beta was determined by Genescan fragment analysis using reverse polymerase chain reaction. Serum thyroglobulin (TG) antibody concentrations were measured and the extent of lymphocytic infiltration of one thyroid lobe was histologically graded.

RESULTS

Fas and FasL gene expression was significantly higher in rats with LT and correlated with the extent of lymphocytic infiltration and the TG antibody level. There was no evidence that the expression of IL-1beta or other cytokines is related to the expression of Fas or its ligand.

CONCLUSIONS

The increased expression of Fas and FasL in LT of BB/W rats suggests the involvement of the Fas pathway in the pathogenesis of LT in BB/W rats. However, in contrast to results of recent in vitro studies, in the BB/W rat Fas/FasL expression is not regulated by IL-2, -4, -6, -10, -12, interferon gamma, and tumor necrosis factor alpha.

A point mutation in the albumin gene in a Chinese patient with familial dysalbuminemic hyperthyroxinemia

Familial dysalbuminemic hyperthyroxinemia (FDH) is an autosomal dominant disorder characterized by euthyroid hyperthyroxinemia. However, FDH has not been reported in Chinese or African patients. Here, we report the first case of FDH in a Chinese patient. A 69-year-old Chinese man was found to have increased serum total T(4) concentrations (198-242nmol/l; normal range 58-148nmol/l) and free T(4) concentrations (>58pmol/l; T(4) analog method, normal range 9-28pmol/l). Serum total T(3) and TSH concentrations were normal. The patient was misdiagnosed as hyperthyroid and was later suspected to have a TSH-producing tumor by the finding of a pituitary microadenoma, which was eventually proven to be a non-functional pituitary 'incidentaloma'. Electrophoretic analysis of the patient's serum proteins demonstrated enhanced albumin binding of [(125)I]T(4). Serum free T(4) concentrations were normal (16-19pmol/l, normal range 9-26pmol/l) when a two-step method was used. Direct sequencing of the albumin gene showed a guanine to adenosine transition in the second nucleotide of codon 218, resulting in a substitution of histidine (CAC) for the normal arginine (CGC) in one of the two alleles in the patient. The point mutation was further confirmed by HphI digestion of exon 7 of the albumin gene. The patient's son was not affected. Our studies demonstrated that the point mutation of the albumin gene in a Chinese patient with FDH was similar to that found in western white families, but differed from that in a Japanese family in whom a guanine to cytosine transition at the same position was found.

Cytokine gene expression in autoimmune thyroiditis in BioBreeding/Worcester rats

The intrathyroidal cytokine gene expression in human autoimmune thyroid disease is difficult to interpret because surgical specimens mostly reflect the autoimmune disease at a late stage. Because it is not possible to investigate early stages of thyroiditis in humans, the Bio Breeding/Worcester (BB/W) rat was used as a model. To characterize the lymphocytic thyroiditis (LT) of BB/W rats further and to evaluate early increases of cytokine gene expression in LT, we investigated the interleukin (IL)-2, -4, -6, -10, -12p40, interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) gene expression in the thyroids, spleens, and livers of BB/W rats with and without histological evidence for thyroiditis. The gene expression of these cytokines was determined by Genescan (PE Applied Biosystems, Foster City, CA) fragment analysis using reverse polymerase chain reaction (RT-PCR). Serum thyroglobulin (Tg) antibody concentrations were measured and the extent of lymphocytic infiltration of one thyroid lobe was histologically graded. Cytokine gene expression in rats with and without LT was compared in three groups of rats: 55-day-old rats after 24 days of iodine administration, 75-day-old rats after 45 days of iodine administration, and 101-day-old rats. In the thyroids of the BB/W rats no expression of IL-4 or IL-10 was detectable. The number of rats with detectable TNF-alpha, IFN-gamma, IL-2, IL-12p40 gene expression was significantly higher in rats with LT. Rats with LT had significantly higher IL-12p40 mRNA levels. There were no significant differences in the IL-6 gene expression between rats with and without LT. A correlation between the level of lymphocytic infiltration and the TNF-alpha (r = 0.56, p < 0.0065) and TG antibody concentration (r = 0.62, p < 0.0065) was found. Therefore, the early cytokine gene expression in the BB/W rat is characterized by Th1-related cytokines like IL-2 and IFN-gamma. Whether the detected IL-12p40 (10 rats) and IFN-gamma (5 rats) gene expression in animals without LT is an early indicator for the development of LT remains to be determined.

Expression of multiple thyroid hormone receptor isoforms in rat femoral and vertebral bone and in bone marrow osteogenic cultures

Thyroid hormones influence both bone formation and bone resorption. Clinical data and animal studies provide evidence of skeletal site heterogeneity (hip vs. spine) of bone responses to thyroid hormones. In vitro studies also demonstrate direct effects of thyroid hormones on cells of the osteoblast lineage. Transcriptional regulation by thyroid hormone is mediated by ligand-dependent transcription factors called thyroid hormone receptors (TRs). Two genes, c-ErbAalpha and c-ErbAbeta, generate at least four TR isoforms in the rat: TRalpha(1), c-erbAalpha(2), TRbeta(1), and TRbeta(2). Although functional TRs have been identified in cells of the osteoblast lineage, it is still not known if TR isoform expression in bone differs depending upon which skeletal site is examined. We have used ribonuclease protection assay and Northern blot analysis to simultaneously examine the expression of TR isoform mRNAs in adult rat femoral and vertebral bone. TRalpha(1), c-erbAalpha(2), and TRbeta(1) are expressed in both femur and vertebra whole bone. Bone marrow cells from both skeletal sites were also cultured under conditions whereby the osteoprogenitors differentiated into osteoblasts and formed a mineralized extracellular matrix. TRalpha(1), c-erbAalpha(2), and TRbeta(1) mRNAs are each expressed in both femoral and vertebral osteoblast cultures. The presence of TRalpha(1), c-erbAalpha(2), and beta(1) proteins was confirmed by Western analysis of nuclear protein extracts from femoral and vertebral cell cultures. These results indicate that the three predominant TR isoforms are highly expressed in bone and osteoblasts from femurs and vertebrae. Whether there are distinct mechanisms of thyroid hormone action mediated by TRalpha(1), c-erbAalpha(2), and TRbeta(1) at these separate skeletal sites remain to be shown.

Monomorphic teratoma of the ovary: a rare cause of triiodothyronine toxicosis

A case of low thyroid radioactive iodine uptake (RAIU) thyrotoxicosis due to a large struma ovarii comprising pure thyroid tissue is presented, including a detailed diagnostic evaluation, histopathology, and demonstration of rapid recovery of native thyroid function after surgical excision. In addition, the first comprehensive analysis of thyroglobulin obtained from an ovarian struma is reported.

Induction of transcription factor interferon regulatory factor-1 by interferon-gamma (IFN gamma) and tumor necrosis factor-alpha (TNF alpha) in FRTL-5 cells

While it is well known that interferon-gamma (IFN gamma) and tumor necrosis factor-alpha (TNF alpha) play a role in the regulation of thyroid growth and differentiated functions, the cellular and molecular mechanisms involved in mediating the effects of IFN gamma and TNF alpha on thyroid function are unknown. In the present study, we used FRTL-5 rat thyroid cells to examine the effects of IFN gamma and TNF alpha on gene expression of transcription factor interferon regulatory factor-1 (IRF-1), which is involved in mediating the effects of these cytokines in a number of cell types. Northern blot analysis of FRTL-5 mRNA showed a single IRF-1 mRNA at 2.2 Kb. In quiescent FRTL-5 cells, IRF-1 mRNA levels were low but detectable by Northern analysis. Incubation of FRTL-5 cells with IFN gamma or TNF alpha resulted in a dose- and time-dependent increase in IRF-1 mRNA levels. We have shown that TNF-alpha and IFN-gamma act synergistically to block the TSH-induced increase in type I 5'-deiodinase(5'D-I) activity and 5'D-I gene expression in FRTL-5 rat thyroid cells. Incubation of FRTL-5 cells with IFN gamma and TNF alpha in combination, however, did not synergistically increase IRF-1 mRNA levels. Electrophoretic mobility shift assay (EMSA) revealed that IFN gamma induced the formation of a single complex to a IFN gamma activation site (GAS) probe in a dose dependent manner. Several lines of evidence suggest that TNF alpha activates transcription factor nuclear factor-kappa B (NF kappa B) through activation of protein kinase C (PKC) or the hydrolysis of sphingomyelin to ceramide in a number of cell types. Here we demonstrate that hydrolysis of sphingomyelin to ceramide by sphingomyelinase (SMase), but not activation of PKC by 12-O-tetradecanoylphorbol 13-acetate (TPA), was involved in the activation of NF kappa B in FRTL-5 cells. Similarly, hydrolysis of sphingomyelin to ceramide, but not activation of PKC, resulted in an increased in IRF-1 mRNA levels in FRTL-5 cells. The present data demonstrate that IFN gamma and TNF alpha increase IRF-1 mRNA levels in FRTL-5 cells through activation of GAS and NF kappa B binding proteins, respectively. Thus, our results suggest that upregulation of IRF-1 may play a role in mediating the effects of IFN gamma and TNF alpha on thyroid function. Our results also suggest that the induction of IRF-1 mRNA by IFN gamma and TNF alpha is not the cellular mechanism involved in the synergistic effect of these cytokines on thyroid function.

The oral administration of human thyroglobulin does not affect the incidence of lymphocytic thyroiditis in the biobreeding Worcester rat

Oral tolerization with the appropriate antigen(s) to ameliorate autoimmune diseases in humans and in experimentally induced animal models, including experimentally autoimmune thyroiditis in mice, has been reported to be efficacious. Spontaneous and iodine induced (0.05% iodine in the drinking water) lymphocytic thyroiditis (LT) occurs in the diabetes mellitus (DM)-prone BioBreeding/Worcester (BB/Wor) rat. The present study was carried out to determine whether the oral administration of human thyroglobulin (hTg) would decrease the incidence of spontaneous and iodine-induced LT in the BB/Wor rat. Low iodine content hTg or bovine serum albumin (BSA) were given orally every 2 days for six doses beginning at age 50 days to BB/W rats, half of whom also received iodine in their drinking water. No effect or orally administered hTg was observed on thyroid weight, the incidence of LT or DM, or on serum thyroglobin antibodies (TgAb), thyrotropin (TSH), thyroxine (T4), and triiodothyronine (T3) concentrations when rats were killed at 100 days of age. In a second experiment, the oral administration of iodine rich hTg or BSA every 2 days for six doses beginning at 30 days of age to iodine-treated BB/Wor rats again did not affect the high incidence of LT or DM or serum TgAb, TSH, T4, and T3 concentrations. The present study suggests that oral tolerization with hTg does not affect spontaneous or iodine-induced lymphocytic thyroiditis or serum thyroglobulin antibodies in the BB/Wor rat.

Escape from the acute Wolff-Chaikoff effect is associated with a decrease in thyroid sodium/iodide symporter messenger ribonucleic acid and protein

In 1948, Wolff and Chaikoff reported that organic binding of iodide in the thyroid was decreased when plasma iodide levels were elevated (acute Wolff-Chaikoff effect), and that adaptation or escape from the acute effect occurred in approximately 2 days, in the presence of continued high plasma iodide concentrations. We later demonstrated that the escape is attributable to a decrease in iodide transport into the thyroid, lowering the intrathyroidal iodine content below a critical inhibitory threshold and allowing organification of iodide to resume. We have now measured the rat thyroid sodium/iodide symporter (NIS) messenger RNA (mRNA) and protein levels, in response to both chronic and acute iodide excess, in an attempt to determine the mechanism responsible for the decreased iodide transport. Rats were given 0.05% NaI in their drinking water for 1 and 6 days in the chronic experiments, and a single 2000-microg dose of NaI i.p. in the acute experiments. Serum was collected for iodine and hormone measurements, and thyroids were frozen for subsequent measurement of NIS, TSH receptor, thyroid peroxidase (TPO), thyroglobulin, and cyclophilin mRNAs (by Northern blotting) as well as NIS protein (by Western blotting). Serum T4 and T3 concentrations were significantly decreased at 1 day in the chronic experiments and returned to normal at 6 days, and were unchanged in the acute experiments. Serum TSH levels were unchanged in both paradigms. Both NIS mRNA and protein were decreased at 1 and 6 days after chronic iodide ingestion. NIS mRNA was decreased at 6 and 24 h after acute iodide administration, whereas NIS protein was decreased only at 24 h. TPO mRNA was decreased at 6 days of chronic iodide ingestion and 24 h after acute iodide administration. There were no iodide-induced changes in TSH receptor and thyroglobulin mRNAs. These data suggest that iodide administration decreases both NIS mRNA and protein expression, by a mechanism that is likely to be, at least in part, transcriptional. Our findings support the hypothesis that the escape from the acute Wolff-Chaikoff effect is caused by a decrease in NIS, with a resultant decreased iodide transport into the thyroid. The observed decrease in TPO mRNA may contribute to the iodine-induced hypothyroidism that is common in patients with Hashimoto's thyroiditis.

Effects of iodine repletion on thyroid morphology in iodine and/or selenium deficient rat term fetuses, pups and mothers

It has been suggested that selenium deficiency aggravates the iodine-induced thyroid inflammation and necrosis in iodine-deficient Wistar rats and possibly in man. Studies were carried out to determine whether large amounts of iodine given to iodine-deficient pregnant Sprague-Dawley rats with or without selenium deficiency would induce inflammation and necrosis in their term fetal thyroids. Iodine deficiency was induced in the dams by a low iodine diet or perchlorate in the drinking water and iodine excess was achieved by iodinated drinking water during pregnancy or daily subcutaneous injections of iodine from days 20 to 22 of pregnancy, 1 day after perchlorate was discontinued. Studies were also carried out in 30-day-old pups whose nursing mothers were iodine-deficient (perchlorate) with or without selenium deficiency from conception onward. The administration of iodine restored the morphologic changes in the thyroid induced by iodine deficiency, irrespective of selenium status, toward normal without inflammatory changes or necrosis. Possible explanations for these unexpected findings are discussed.

Thyroid health status of ammonium perchlorate workers: a cross-sectional occupational health study

Since pharmaceutical exposures to perchlorate are known to suppress thyroid function in patients with hyperthyroidism, a study of employees at a perchlorate manufacturing plant was conducted to assess whether occupational exposure to perchlorate suppresses thyroid function. Exposure to perchlorate was assessed by measurement of ambient air concentrations of total and respirable perchlorate particles, and systemic absorption was assessed by measurement of urinary perchlorate excretion. Airborne exposures ranged from 0.004 to 167 mg total particulate perchlorate per day. Urinary perchlorate measurements demonstrated that exposure to the airborne particulate perchlorate resulted in systemic absorption. Workers were grouped into four exposure categories with mean absorbed perchlorate dosages of 1, 4, 11 and 34 mg perchlorate per day. Thyroid function was assessed by measurement of serum thyroid-stimulating hormone, free thyroxine index, thyroxine, triiodothyronine, thyroid hormone binding ratio, thyroid peroxidase antibodies, and by clinical examination. No differences in thyroid-function parameters were found between the four groups of workers across approximately three orders of magnitude of exposure and of dose. Thus human thyroid function was not affected by these levels of absorbed perchlorate. In addition, no clinical evidence of thyroid abnormalities was found in any exposure group. The blood-cell counts were normal in all groups, indicating no evidence of hematotoxicity in this exposure range. The absence of evidence of an effect on thyroid function or blood cells from occupational airborne perchlorate exposure at a mean absorption of 34 mg/day demonstrates a no-observed-adverse-effect-level (NOAEL) that can assist in the evaluation of human health risks from environmental perchlorate contamination.

Are thyroid function tests too frequently and inappropriately requested?

In spite of data supporting the use of the serum thyrotropin (TSH) concentration as the best test to detect abnormal thyroid function, measurement of circulating thyroid hormones with or without a serum TSH continues to be frequently requested to evaluate thyroid function. We have analyzed how combinations of thyroid function tests were ordered by referring physicians and the results of the tests in order to offer some suggestions as to how to use thyroid function tests in a cost effective manner. During 1995, 19,181 inpatient and outpatient requests (45,865 different tests) for thyroid function tests were received by the laboratory of a 1600 bed University Hospital in Parma, Italy. The following tests were carried out: T4, free T4, T3, free T3 and TSH. Serum TSH values below and above the normal range were considered to reflect abnormal thyroid function i.e. hyperthyroidism, or hypothyroidism including subclinical disease independent of the results of the other tests. Combinations of ordered tests and the percent of the total for each combination were: TSH+T4+T3 (56%), TSH+FT4+FT3 (14%), TSH (12%), TSH+FT4 (9%), TSH+T4 (1%), TSH+T4+T3+FT4+FT3 (5%), others (3%). The T4+T3+TSH panel (10,780 requests) had normal serum TSH values in 80.6% and the FT4+ FT3+TSH panel (2,590 requests) had normal TSH values in 73.2%. Elevated serum TSH concentrations were observed more frequently in hospitalized than in ambulatory patients (9.7% vs 7.4% p<0.001). T3 (elevated serum T3, normal T4 and low TSH concentrations) and T4 (elevated serum T4, normal T3 and low TSH concentrations) toxicosis were observed in 8.1% and 9.4%, respectively, of the requested test (NS). FT3 and FT4 toxicosis, defined as for T3 and T4 toxicosis, were observed in 7.5% and 4.9%, respectively (NS). The low T3 and low FT3 syndrome in hospitalized patients was present in 1.6% and 2.3% of the requests, respectively (NS). The low T4+low T3 and low FT4+low FT3 syndrome was present in only 0.3% and 0.2%, respectively, of the requests. Our study shows that a) in hospitalized patients thyroid function tests were requested in 20% of the patients and only one in 14 of these patients at the highest could have abnormal thyroid function, as indicated by abnormal TSH value b) FT4 (or T4) is as useful as FT3 (or T3) in the diagnosis of hyperthyroidism, c) in hospitalized patients the low T3 syndrome was far less common than that reported in the literature, probably due to the lower severity of illness, d) panels which include T3 and FT3 are not justified, and e) serum TSH alone is the most appropriate initial thyroid function test.

Identification of Grb4/Nckbeta, a src homology 2 and 3 domain-containing adapter protein having similar binding and biological properties to Nck

Adapter proteins made up of Src homology (SH) domains mediate multiple cellular signaling events initiated by receptor protein tyrosine kinases. Here we report that Grb4 is an adapter protein closely related to but distinct from Nck that is made up of three SH3 domains and one SH2 domain. Northern analysis indicated that both genes are expressed in multiple tissues. Both Nck and Grb4 proteins could associate with receptor tyrosine kinases and the SH3-binding proteins PAK, Sos1, and PRK2, and they synergized with v-Abl and Sos to induce gene expression via the transcription factor Elk-1. Although neither protein was transforming on its own, both Nck and Grb4 cooperated with v-Abl to transform NIH 3T3 cells and influenced the morphology and anchorage-dependent growth of wild type Ras-transformed cells. Nck and Grb4 therefore appear to be functionally redundant.

Recombinant interferon alpha (rIFN-alpha) does not potentiate the effect of iodine excess on the development of thyroid abnormalities in patients with HCV chronic active hepatitis

OBJECTIVE

To determine whether the administration of pharmacological quantities of iodine during interferon-alpha (rIFN-alpha) treatment of chronic viral hepatitis B and C (HCV) would exacerbate the potential adverse effects of rIFN alpha on thyroid function.

DESIGN

Thyroid function tests were carried out in 48 euthyroid patients before and during rIFN-alpha therapy of HCV. Twenty-one of these patients were also treated with 10 drops saturated solution of potassium iodine (SSKI, approximately 350 mg iodine daily). Eight patients with HCV but not treated with rIFN-alpha received 10 drops SSKI.

PATIENTS

All patients were enthyroid prior to rIFN-alpha therapy for HCV or iodine and thyroid function tests were similar in the three groups.

MEASUREMENTS

Serum free T4, free T3, and TSH concentrations were measured prior to and at 30 and 60 days of rIFN-alpha therapy in the three groups of patients. The serum TSH response to TRH was assessed before rIFN-alpha therapy and on day 60. Thyroid peroxidase antibodies were measured before and during therapy.

RESULTS

During the 2-month study period, similar small but significant decreases in serum FT4 and FT3 and compensatory small significant increases in TSH concentrations were observed in the patients treated with rIFN-alpha + iodine and iodine alone but not in the patients receiving rIFN-alpha alone. Abnormal thyroid function tests were observed more frequently in patients receiving rIFN-alpha + iodine and iodine alone compared to those receiving rIFN-alpha alone.

CONCLUSIONS

Excess iodine administered to patients treated with rIFN-alpha induced small changes in thyroid function similar to those observed in patients treated with iodine alone. Thus, rIFN-alpha and iodine do not appear to be synergistic in the development of abnormal thyroid function tests over a 2-month treatment period.

Ammonium persulfate: a new and safe method for measuring urinary iodine by ammonium persulfate oxidation

The chloric acid method is most commonly used to obtain accurate and reproducible measurements of iodine and removes interfering substances. Unfortunately, chloric acid is a potential hazard requiring an explosion proof hood among other precautions. We have developed a simple, convenient, and economic method for measuring urinary iodine using 1 mol/L ammonium persulfate, a non-explosive, non-hazardous chemical, as the oxidizing reagent. The oxidation procedure can be completed in 30 minutes at a temperature of 91-95 degrees C. The iodine in the urine is then measured by a modification of the traditional colorimetric method of Sandell-Kolthoff. 110 urine samples collected from a mixed population of healthy males and females, ranging in age from 6 to 79 years and living in the United States were analyzed for iodine content by two methods: the proposed ammonium persulfate method and the chloric acid method. The ammonium persulfate method has an intra assay CV of 9.1% at 0.42 +/- 0.04 micromol/L (mean +/- SD), 7.8% at 1.46 +/- 0.11 micromol/L and 4.0% at 3.54 +/- 0.14 micromol/L. The inter assay CV is 10.2% at 0.46 +/- 0.05 micromol/L and 7.9% at 3.27 +/- 0.26 micromol/L. Recovery of iodine added to urine in vitro was 107%, 94% and 97% for 0.42 micromol/L, 0.77 micromol/L and 3.64 micromol/L, respectively. The lower limit of detectability was 0.0034 microgI. Values for iodine in 110 urines measured by the reference chloric acid method ranged from 0.06 to 8.03 micromol/L and by the ammonium persulfate method from 0.05 to 7.4 micromol/L. The persulfate method (y) correlated extremely closely with the reference chloric acid method (x) by the Pearson correlation (y = 0.923x + 0.810 micromol/L, and r = 0.994, Syx = 1.841). In conclusion a new, safe, simple method for measuring urinary iodine is described which uses ammonium persulfate as the oxidizing agent for the removal of interfering substances.

Increased expression of tumor necrosis factor-alpha and decreased expression of thyroglobulin and thyroid peroxidase mRNA levels in the thyroids of iodide-treated BB/Wor rats

Several lines of evidence suggest that tumor necrosis factor-alpha (TNFalpha) may contribute to the pathogenesis of autoimmune thyroid disease. It is not known, however, whether increased thyroidal TNFalpha levels are associated with changes in thyroid function. The purpose of the present study was to utilize in situ hybridization histochemistry and immunohistochemistry to determine if the expression of TNF-alpha in the thyroid is associated with a decrease in thyroglobulin (Tg) and thyroid peroxidase (TPO) mRNA levels. Lymphocytic thyroiditis was induced in BB/Wor rats by iodide administration, and thyroidal Tg and TPO mRNA levels were assessed by Northern blot analysis and in situ hybridization, and TNFalpha expression by Northern blot analysis and immunohistochemistry. Thyroids were obtained before and 1 and 2 months after iodide administration. Hematoxylin and eosin staining revealed that there was a progressive increase in mononuclear cells in the thyroids of BB/Wor rats ingesting iodide for 1 and 2 months. Northern blot analysis revealed that during the same time course there was a progressive increase in TNFalpha mRNA levels and a progressive decrease in Tg and TPO mRNA levels in the thyroids. In situ hybridization histochemistry was performed to determine if the decrease in Tg and TPO mRNA levels was associated with thyroid follicular cells in contact with infiltrating mononuclear cells. In rats treated with iodide for 1 month, there was a modest decrease in Tg and TPO mRNA levels in follicular cells in contact with infiltrating mononuclear cells. After 2 months of iodide treatment there was clearly a localized decrease in Tg and TPO mRNA levels in follicular cells in contact with infiltrating mononuclear cells. Immunohistochemical analysis did not detect TNFalpha in the thyroids from control rats or from rats treated with iodide for 1 month. In contrast, after 2 months of treatment, TNFalpha was easily detected in infiltrating mononuclear cells and in some thyroid follicular cells. Together, these results suggest that the suppression of Tg and TPO mRNA levels was associated with the expression of TNFalpha and thus are in agreement with in vitro studies demonstrating that TNFalpha inhibits thyroid cell function.

Circulating iodide concentrations during and after pregnancy

Early, indirect studies suggested that an important aspect of thyroid economy during pregnancy was a decline in plasma or serum inorganic iodide (PII) concentrations, but there is little information concerning circulating iodide concentrations as assessed by direct measurement. The present study was undertaken to determine the relationship between gestation and serum iodide concentrations as assessed by direct measurement of PII. PII concentrations, urinary iodide levels, and other parameters of thyroid economy were measured during the first, second, and third trimesters and after delivery in 16 women. Mean serum T4 concentrations were significantly higher in all 3 trimesters than those after delivery. Serum free T4 index concentrations were significantly higher in the first trimester than during later periods of gestation or after delivery, but serum TSH concentrations were not depressed in the first trimester. Serum thyroglobulin concentrations were similar during pregnancy and after delivery. There was wide variability in PII and urinary iodide concentrations during and after pregnancy, but there was no trend for PII concentrations to be depressed during pregnancy. Pregnancy, at least in iodine-sufficient regions, does not have an important influence on circulating concentrations of iodide.

Iodine nutrition in the United States. Trends and public health implications: iodine excretion data from National Health and Nutrition Examination Surveys I and III (1971-1974 and 1988-1994)

Iodine deficiency in a population causes increased prevalence of goiter and, more importantly, may increase the risk for intellectual deficiency in that population. The National Health and Nutrition Examination Surveys [NHANES I (1971-1974) and (NHANES III (1988-1994)] measured urinary iodine (UI) concentrations. UI concentrations are an indicator of the adequacy of iodine intake for a population. The median UI concentrations in iodine-sufficient populations should be greater than 10 microg/dL, and no more than 20% of the population should have UI concentrations less than 5 microg/dL. Median UI concentrations from both NHANES I and NHANES III indicate adequate iodine intake for the overall U.S. population, but the median concentration decreased more than 50% between 1971-1974 (32.0+/-0.6 microg/dL) and 1988-1994 (14.5+/-0.3 microg/dL). Low UI concentrations (<5 microg/dL) were found in 11.7% of the 1988-1994 population, a 4.5-fold increase over the proportion in the 1971-1974 population. The percentage of people excreting low concentrations of iodine (UI, <5 microg/dL) increased in all age groups. In pregnant women, 6.7%, and in women of child-bearing age, 14.9% had UI concentrations below 5 microg/dL. The findings in 1988-1994, although not indicative of iodine deficiency in the overall U.S. population, define a trend that must be monitored.