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PubMed1984

Normal serum thyroxine values in patients with acute psychiatric illness.

The medical records of 278 consecutive patients with acute psychiatric illness admitted to a closed psychiatric unit after admission from the emergency room were reviewed. Serum thyroxine levels had been determined within 72 hours of admission in 106 patients (38 percent); in 74 of these patients (70 percent), the determination had been made within 24 hours. Ten patients (9 percent) were hypothyroxinemic, but further thyroid testing revealed that they were functionally euthyroid. Only one patient had hyperthyroxinemia, which was considered secondary to her postpartum state. The prevalence of hypothyroxinemia in the population studied is consistent with that in previous reports. However, the striking absence of hyperthyroxinemia in these patients is contrary to findings in several recent reports. Further prospective studies should clarify this issue.

Adolescent↗
PubMed1987

Thyroid function in "yusho" patients exposed to polychlorinated biphenyls (PCB).

Thyroid function was investigated in 123 yusho patients who were exposed to toxic levels of polychlorinated biphenyls (PCBs) 16 years ago. In yusho patients, compared with the patients without evidence of yusho or normal controls, the serum triiodothyronine (T3) and thyroxine (T4) levels were significantly higher, while thyroid stimulating hormone (TSH) levels measured by sensitive assay were normal. There was no difference in serum levels of albumin, alkaline phosphatase, total cholesterol, and thyroxine binding globulin (TBG) between the two groups and the prevalence of positive antithyroid autoantibodies was almost the same, suggesting that hyperthyroxinemia in yusho patients was not due to increased TBG binding or abnormal autoimmune mechanism. Serum free T4 levels, however, were not elevated, although T4/TBG ratio was significantly higher. The thyroid hormone levels were higher than normal value in 4 of 123 yusho patients but only 1 case had clinical symptoms such as excessive perspiration. Despite higher serum PCBs in yusho patients, there was no correlation between PCB levels and levels of T3, T4, or TSH. The present results suggest hyperthyroxinemia without obvious clinical symptoms in yusho patients long after exposure to PCBs.

Adult↗
PubMed1997

The effect of in vivo thyroxine treatment on insulin receptors, glucose transport and GLUT4 in rat adipocytes.

Daily i.p. administration of thyroxine (T4; 50 micrograms/100 g BW) to adult male rats for one week doubled the thyroxinemia and induced significant augmentation of glycemia and insulinemia. Hyperthyroxinemia was also manifested by significant elevation of liver malic enzyme activity and by the presence of smaller fat cells. Adipocytes of T4 treated rats displayed significantly lower density of insulin receptors, decreased insulin stimulatory effect on glucose transport and less glucose transporter (GLUT4) protein in plasma membranes after insulin stimulation as those of controls. These results indicate a deleterious effect of hyperthyroxinemia on insulin controlled glucose metabolism in fat cells.

Adipocytes↗
PubMed1992

A novel variant of transthyretin (prealbumin), Thr119 to Met, associated with increased thyroxine binding.

A group of patients with prealbumin associated hyperthyroxinemia possess a common single base substitution in the fourth exon of their transthyretin gene. This cytosine to thymine substitution occurs in the codon for residue 119 and results in the predicted replacement of a threonine residue with a methionine at this position. A new NcoI restriction endonuclease cleavage site is created by the point mutation and can be detected by a rapid and simple assay based on the polymerase chain reaction. This variant transthyretin is inherited in an autosomal dominant manner and is apparently not amyloidogenic but is associated with increased thyroxine binding. As healthy heterozygous individuals have normal serum thyroxine concentrations, the hyperthyroxinemia sometimes found may not be primarily due to the variant.

Base Sequence↗
PubMed1992

Variations in thyroid hormone transport proteins and their clinical implications.

Variations in major thyroid hormone transport proteins may be inherited or acquired and may be associated with changes in serum concentration of the proteins or their affinity for thyroid hormones. These variations most frequently involve thyroxine-binding globulin (TBG), but changes in transthyretin and albumin are also observed. The consequent alteration of thyroid hormone-binding capacity in serum is associated with variations in total thyroid hormone concentration. Increased serum total thyroid hormone levels are found in subjects with TBG excess, familial dysalbuminemic hyperthyroxinemia, and transthyretin-associated hyperthyroxinemia. Conversely, diminished serum thyroid hormone values are observed in subjects with TBG deficiency, and decreased concentration or affinity of transthyretin and albumin is not associated with variations in serum concentrations of thyroid hormones. The transport protein-associated variations in serum total thyroid hormone concentrations do not reflect a change in thyroid status. Euthyroidism can be easily established in subjects with transport protein abnormalities by the normal free thyroid hormone and TSH concentrations. It is, however, crucial to select methods for free thyroid hormone measurement that are not affected by abnormalities of transport proteins. Some assays, such as the analog method, often provide artifactual and misleading results, which may lead to inappropriate and even detrimental treatments. The evolutionary advantage of TBG (and albumin) in terms of thyroid homeostasis still remains to be elucidated.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Toxic hematoma: an unusual and previously undescribed type of thyrotoxicosis.

The present case describes a new and unusual variant of thyrotoxicosis: transient hyperthyroxinemia following acute and massive hemorrhage into a previously normal thyroid gland. A 74-year-old woman presented with a large painful neck mass, palpitations, rapid atrial fibrillation, and hyperthyroxinemia following a fall and neck trauma while treated with excessive oral anticoagulants. Ultrasound and computerized tomography of the neck were consistent with a massive intrathyroidal hematoma. Elevation in serum T4 and T3 levels with suppressed TSH normalized over 3-4 weeks in parallel with hematoma shrinkage. Her tests were consistent with extensive bleeding into thyroidal tissue producing release of stored hormone. Her clinical course was compatible with the known disappearance rate of thyroxine and she returned to her euthyroid status without antithyroid therapy.

Aged↗
PubMed1996

Measurement of serum free thyroid hormone concentrations: an essential tool for the diagnosis of thyroid dysfunction.

Free thyroid hormones (free thyroxine, FT4, and free triiodothyronine, FT3) represent a more useful index of thyroid status than total thyroid hormones, because the latter are influenced by variations of thyroid hormone-binding proteins, especially T4-binding globulin (TBG). Thus, increased serum total T4 (TT4) and, in many instances, T3 (TT3) concentrations are encountered in euthyroid subjects with TBG excess, familial dysalbuminemic hyperthyroxinemia and transthyretin-associated hyperthyroxinemia, while decreased serum TT4 and TT3 levels are associated with TBG deficiency: under these circumstances, measurement of serum FT4 and FT3 levels correctly establishes the diagnosis of euthyroidism. In cases of suspected hyperthyroidism, a diagnostic strategy can be suggested based on serum FT3 (and TSH) measurement, since FT4 may occasionally be elevated, also in euthyroid subjects, e.g., in patients under chronic amiodarone or L-T4 treatment. When hypothyroidism is suspected, the most reliable test appears to be FT4 (together with TSH), because FT3 may still be normal in patients with subclinical or mild thyroid failure. In any case, it is essential that reliable free thyroid hormone assays be used, which are devoid of methodological limitations responsible for artifactual results under particular circumstances, such as thyroid hormone-binding protein abnormalities, pregnancy and nonthyroidal illness.

Artifacts↗
PubMed1990

Different effects of thyroid disease on serum levels of procollagen III N-peptide and hyaluronic acid.

Serum levels of procollagen III N-peptide (PIIINP) and hyaluronic acid (HA) reflect secretion of procollagen III and HA from fibroblasts, a cell type sensitive to thyroid hormones. Serum PIIINP and HA concentrations were measured in different thyroid function states, the former by two different assays, one detecting intact and aggregated PIIINP (PIIINP assay) and another detecting low mol wt degradation products of PIIINP as well (Fab-PIIINP assay). Two thirds of 28 hyperthyroid patients had elevated serum PIIINP values (mean, 192% in the PIIINP assay and 243% in the Fab-PIIINP assay) compared to age- and sex-matched controls (P less than 0.001). Normalization was seen after medical treatment (n = 16). In contrast, serum HA levels increased from 49 +/- 30 to 68 +/- 37 ng/mL (P less than 0.01) when a euthyroid state was achieved. Hypothyroid patients (n = 23) had increased serum HA levels (mean, 162%; P less than 0.05), which normalized after L-T4 treatment (71 +/- 50 before and 41 +/- 20 ng/mL after treatment (n = 16; P less than 0.02). L-T4 treatment also increased serum PIIINP levels significantly. Subjects with familial dysalbuminemic hyperthyroxinemia (n = 8), representing a situation with elevated circulating levels of T4 due to enhanced protein binding, and patients with nontoxic goiter with serum TSH levels ranging from 3.6-0.05 mU/L had normal serum levels of PIIINP and HA. Our data suggest that the secretion of procollagen III and that of HA from fibroblasts are influenced differently by thyroid hormones, since the secretion of procollagen III seems enhanced by thyroid hormones, whereas the secretion of HA seems reduced. Neither euthyroidism with enhanced serum T4 levels (familial dysalbuminemic hyperthyroxinemia) nor euthyroidism with reduced serum TSH levels (nontoxic goiter) seems associated with alterations at the connective tissue level.

Adolescent↗
PubMed1993

Studies of thyroid xenografts from Graves' disease in severe combined immunodeficient mice.

Thyroid tissues from normal (paranodular) subjects and patients with Graves' disease (GD) and Hashimoto's thyroiditis (HT) were xenografted to severe combined immunodeficiency (SCID) mice, and the same tissues were engrafted into nude mice; in addition, peripheral blood mononuclear cells were engrafted to separate SCID mice (SCID-PB). Thyroglobulin (TG) and microsomal antibodies (Abs) became detectable with high titers by hemagglutination assays in SCID mice xenografted with thyroid tissues (SCID-TH) from GD and HT patients; moreover, TG Ab was detectable even in SCID-TH from TG Ab-negative GD and HT donors. On the other hand, only 2 of 10 SCID-PB had detectable Abs with low titers. TSH receptor (TSH-R) Ab was detectable in all sets of SCID-TH from GD. After peaking (3-7 weeks), their levels decreased despite the fact that immunoglobulin G levels increased. In addition, in 3 of 4 sets of SCID-PB from GD patients, TSH-R Ab was also detectable. SCID-TH from GD and HT patients showed transient hyperthyroxinemia, peaking at 2 weeks; these values were significantly higher [free T4, 6.48 +/- 0.90 and 5.50 +/- 0.77 pmol/L (mean +/- SE), respectively; P < 0.05] than SCID-TH from normal controls (2.5 +/- 0.24). Histologically, intrathyroidal infiltrating lymphocytes (ITL) survived in SCID mice, but not in nude mice after 8 weeks. The follicles of GD tissue in SCID mice were virtually destroyed with ITL, and their appearance was similar to that in HT. In conclusion, TSH-R Ab was clearly produced from ITL, and some peripheral blood mononuclear cells grafts could also produce TSH-R Ab. In spite of the presence of TSH-R Ab, SCID-TH from GD patients did not show persistent hyperthyroxinemia, presumably because destructive thyroiditis may be occurring in the grafted tissue, with decreasing levels of TSH-R Ab.

Animals↗
PubMed1995

Structural and functional differences in the dio1 gene in mice with inherited type 1 deiodinase deficiency.

The type 1 deiodinase (D1) provides the major portion of the circulating T3 in vertebrates. In C3H and certain other inbred mice, liver and kidney D1 activity is 5- to 10-fold lower than in the common phenotype, C57. The lower D1 levels are paralleled by a decreased normal-sized dio1 mRNA and hyperthyroxinemia. Low activity cosegregates with a restriction fragment length variant (RFLV) in both inbred and recombinant strains, indicating it is due to differences in the dio1 gene. The exonic structure and the deduced amino acid sequences are identical for both strains and highly homologous to that of the rat. The RFLV is due to an approximately 150-base pair expansion of repetitive sequences in the second intron of the C3H gene, but this segment does not differentially affect the transient expression of a human GH gene. The promoter and 5'-flanking regions of the C3H and C57 dio1 genes are very similar and are GC rich without TATA or CCAAT boxes. However, functional assays of 1.5-kilobase 5'-flanking dio1-CAT constructs showed 2- to 3-fold higher activity of the C57-CAT constructs. Deletion mutants showed that sequences between -705 and -162 were the cause of this. In this region, the only major difference between the two genes is a 21-base pair insert containing five CTG repeats in the C3H promoter. This difference also cosegregates with low D1 activity and the intron RFLV in four other mouse strains. The correlation of the CTG repeat insert with both in vitro and in vivo expression and the absence of other significant sequence differences in the 5'-flanking region argue that this is the major explanation for the impaired expression of the dio1 gene and the resulting hyperthyroxinemia of the C3H mouse.

Amino Acid Sequence↗
PubMed1983

Familial resistance to thyroid hormone associated with decreased transport across the plasma membrane.

Resistance to thyroid hormone associated with a defect in hormone transport across the plasma membrane occurred in a 74-year-old eumetabolic woman. She had marked elevations in the serum levels of total thyroxine (T4), free T4, and reverse triiodothyronine (rT3). Levels of T3 were only minimally increased. The hyperthyroxinemia was thyrotrophin (TSH) dependent, but was not due to an alteration in the binding of T4 to serum proteins. Refractoriness to thyroxine was only partial, as indicated by the increase in the basal metabolic rate and suppression of the response of TSH to thyrotrophin-releasing hormone (TRH) after the administration of L-thyroxine, 600 micrograms daily, for 3 weeks. The basic abnormality involved a selective decrease of T4 plasma membrane transport shown by in-vitro studies of erythrocytes. Screening of family members showed similar biochemical abnormalities in two other relatives. In this familial syndrome characterized by eumetabolic hyperthyroxinemia, the alteration of thyroid hormone metabolism seems to involve primarily the partition of T4 between the intra- and extracellular spaces.

Adult↗
PubMed2005

[Thyroid dysfunction in long-term amiodarone administration. Correlation of the antiarrhythmic activity of amiodarone with its effect on thyroid function].

Relationship between amiodarone-associated thyroid dysfunction and antiarrhythmic activity of amiodarone was studied in 27 patients (13 with hypothyroidism, 8 with hyperthyroidism, 6 with euthyroid hyperthyroxinemia). Amiodarone-associated hypothyroidism and euthyroid hyperthyroxinemia were not associated with loss of antiarrhythmic efficacy of amiodarone. Hypothyroidism did not require amiodarone withdrawal and therapy with L-thyroxin was conducted at the background of continued amiodarone intake. Achievement of euthyroid state was not followed by recurrence of heart rhythm disturbances. Development of amiodarone-associated thyrotoxicosis was accompanied with loss of antiarrhythmic efficacy of amiodarone in all cases. In 87.5% of patients with thyrotoxicosis correction of the thyroid status was conducted under conditions of continued amiodarone intake as this drug had been given because of life threatening arrhythmias or proven resistance to other antiarrhythmic therapy. In 12.5% of patients it was possible to substitute other drugs for amiodarone. Correction of thyroid status and achievement of euthyroidosis in these patients was associated with restoration of amiodarone antiarrhythmic activity.

Aged↗
PubMed1991

[Effects of yin-tonics and yang-tonics on serum thyroid hormone levels and thyroid hormone receptors of hepatic cell nucleus in hyperthyroxinemic and hypothyroxinemic rats].

Hyperthyroxinemia model was made by giving thyroid tablet suspension to Wistar rats and hypothyroxinemia model was made by thyroidectomy. We measured serum thyroid hormone levels by RIA and the parameters of triiodothyronine receptors in rat hepatic cell nucleus by radio-ligand binding assay: Maximal binding capacity (Bmax) and Dissociation constant (Kd). It is found that (1) Yin-tonics can lower serum thyroid hormone levels and Bmax of hepatic nuclear T3R of hyperthyroxinemia rat from 167.14 +/- 25.62 fmol/100 micrograms DNA to 98.98 +/- 15.24 fmol/100 micrograms DNA, P less than 0.001. (2) Both Yang-tonics I and II can raise serum thyroid hormone levels of hypothyroxinemia rats, but not Bmax of hepatic nuclear T3R. Yang-tonics I even lowers Bmax. All the Chinese herbs have no effect on the Kd of rat hepatic nuclear T3R. The results may have some value in studying the effects of Chinese medical drugs.

Animals↗
PubMed1983

"Unbound analog" radioimmunoassays for free thyroxin measure the albumin-bound hormone fraction.

We have assessed the influence of albumin-bound thyroxin (T4) on apparent free T4 values obtained by two "unbound analog" free T4 methods (AmerlexR Free T4 and Clinical Assays one-step Free T4). We evaluated sera showing three different albumin anomalies: total hereditary analbuminemia, partially corrected analbuminemia, and familial dysalbuminemic hyperthyroxinemia, where abnormal albumin-binding of analog tracer is associated with high apparent free T4 values by these methods. In hereditary analbuminemia, free T4 was almost undetectable by both assays; in contrast, free T4 by equilibrium dialysis was normal. After addition of T4-free human serum albumin, the apparent free T4 concentration in total hereditary analbuminemia became normal by the analog methods. Immunoprecipitation of [125I]T4 and the unidentified labeled kit analogs by antiserum to human albumin was negligible in untreated total hereditary analbuminemia and approximately twice normal in familial dysalbuminemic hyperthyroxinemia. Therefore, alterations in tracer binding to albumin correlate with the apparent free T4 concentrations obtained by the analog methods. The interactions of the unidentified analog tracers and T4 with albumin are such that these techniques principally reflect the albumin-bound T4 moiety.

Antigen-Antibody Complex↗
PubMed2000

Adjuvant effects of cholera toxin b subunit on immune response to recombinant thyrotropin receptor in mice.

We had previously shown that BALB/c mice immunized with the extracellular domain of human thyrotropin receptor (ETSHR) developed moderate hyperthyroxinemia. The antibody responses in these mice were predominantly of the IgG1 subclass. Since cholera toxin B subunit (CT-B) has direct effects on the thyroid, and is known to activate B lymphocytes and cause enhanced IgG1 production, we tested the ability of CT-B to modulate the antibody response to ETSHR. CT-B is unique in that it not only elicits a strong immune response to itself, but more importantly, when given with other antigens acts as a potent adjuvant. In the present study, BALB/c mice given ETSHR with CFA or CT-B via ip route showed higher titers of antibodies to ETSHR when compared to mice similarly immunized with ETSHR alone, or with IFA. Antibodies in ETSHR+CT-B immunized mice were mostly of the IgG1 subclass and reacted predominantly with ETSHR peptides 1 (aa 22-41), 21 (aa 322-341), and 23 (352-371). In contrast, animals immunized with ETSHR+CFA showed IgG1, IgG2a and IgG2b responses and reacted with peptides 1 and 21. Furthermore, mice immunized with ETSHR along with CT-B showed significantly higher levels of thyrotropin (TSH) binding inhibitory immunoglobulins (TBII) compared to those that did not receive CT-B. None of the mice immunized with a control antigen showed antibody response to ETSHR. These results suggested that CT-B could enhance and modulate immune response to ETSHR.

Adjuvants, Immunologic↗
PubMed2000

Familial dysalbuminemic byperthyroxinemia may result in altered warfarin pharmacokinetics.

Two distinct genotypes that result in the amino acid substitutions R218P and R218H in subdomain 2A of human serum albumin (HSA) have been identified as the cause of familial dysalbuminemic hyperthyroxinemia (FDH). These substitutions increase the affinity of subdomain 2A for thyroxine by approximately 10-fold elevating plasma thyroxine levels in affected individuals. While many studies have examined the binding of thyroxine to FDH HSA, the binding of FDH HSA to drugs has not been widely investigated. The widely administered drug warfarin was selected as a model compound to study FDH HSA/drug interactions since it binds to subdomain 2A and its pharmacokinetics are dramatically influenced by HSA binding. Using two independent methods, fluorescence spectroscopy and equilibrium dialysis with radioactive warfarin, the binding of recombinant R218P, R218H, R218M and wild type HSA to warfarin was measured. Both methods showed an approximately 5-fold decrease in the affinity of R218P, R218H and R218M HSA for warfarin relative to wild type HSA. The Kd values determined by fluorescence spectroscopy for wild type, R218H, R218P and R218M HSA binding to warfarin were 1.35, 5.38, 5.61, and 8.34 microM, respectively. The values determined by equilibrium dialysis were 5.36, 29.5, 14.5, and 23.4 microM, respectively. Based on the above findings one would expect the free serum warfarin concentration in homozygous R218P and R218H FDH patients to be elevated about 5-fold, resulting in about a 5-fold reduction in the serum half-life of the drug.

Amino Acid Substitution↗
PubMed1997

Mutagenesis studies of thyroxine binding to human serum albumin define an important structural characteristic of subdomain 2A.

The familial dysalbuminemic hyperthyroxinemia (FDH) phenotype results from a natural human serum albumin (HSA) mutant, with histidine instead of arginine at amino acid position 218. This mutation results in an enhanced affinity for thyroxine. In our earlier study, site-directed mutagenesis and a yeast protein expression system were used to synthesize FDH HSA and several other HSA mutants. Measurement of the binding of these HSA mutants to thyroxine and several thyroxine analogs using equilibrium dialysis and quenching of tryptophan 214 fluorescence allowed us to propose a preliminary model of thyroxine binding to the 2A subdomain of wild type and FDH HSA. In this study, we have produced several other HSA mutants. By comparing the binding affinity of these mutants for thyroxine and tetraiodothyroacetic acid to the binding affinity of other mutants, we were able to suggest a new model for thyroxine binding to the 2A subdomain of HSA. We found that the substitution of arginine at position 218 with alanine increased the binding affinity for thyroxine by 2 orders of magnitude relative to the binding affinity of wild type HSA for thyroxine. A more accurate understanding of the mechanism of thyroxine binding to HSA has allowed us to define an important structural characteristic of subdomain 2A, one of the two principal binding sites on HSA for small hydrophobic ligands.

Arginine↗
PubMed1993

Thyroxine binding in a TTR Met 119 kindred.

Recently, a transthyretin variant, TTR Met 119, in which methionine substitutes for threonine 119, a component of the protein's iodothyronine binding site, was identified in individuals with transient euthyroid hyperthyroxinemia. Healthy carriers of Met 119 have normal serum thyroid hormone concentrations, but two studies of Met 119 carriers have differed as to whether T4 binding to TTR is increased. An additional kindred has been identified by hybrid isoelectric focusing in an ongoing screening program for TTR variants in the Portuguese population with TTR Met 30 associated familial amyloidotic polyneuropathy. Cyanogen bromide peptide mapping and DNA restriction length polymorphism analyses showed that the propositus was a compound heterozygote for two TTR variants: Asn 90 and Met 119. Family analysis revealed that he inherited the TTR Met 119 variant from the mother and the TTR Asn 90 variant from the father. Neither the compound heterozygote nor his parents had symptoms of familial amyloidotic polyneuropathy. Serum dialysis with stepwise saturation of iodothyronine binding sites confirmed that TTR binding of T4 is increased in TTR Met 119. The increased binding is due to a higher TTR concentration rather than an increased association constant for T4. Because of the small proportion of serum T4 bound by TTR, increased T4 binding by TTR did not affect the ratio of free to bound T4 or T4 concentrations. In contrast, plasma retinol binding protein, almost all of which is bound by TTR, was elevated. The Asn 90 mutation does not affect either the concentration or the hormone binding characteristics of the protein. Possible long-term effects of these mutations and the combined heterozygotic state remain to be determined.

Amyloidosis↗