Mechanism of thyroid hormone action.
Explore the source record for details and available documents.
Humans↗
Biomedical subjects
L J DeGroot
Publications and source records attributed to L J DeGroot.
Screening of nineteen unrelated families with generalized resistance to thyroid hormone for known point mutations in the thyroid hormone receptor beta gene and the detection of a new mutation.
Generalized resistance to thyroid hormone (GRTH) is a syndrome characterized by impaired tissue responsiveness to thyroid hormone. Two distinct point mutations in the hormone binding domain of the thyroid hormone receptor (TR) beta have recently been identified in two unrelated families with GRTH. One, Mf, involves a replacement of the normal glycine-345 for arginine in exon 7 and another, Mh, replaces the normal proline-453 for histidine in exon 8. To probe for the presence of the Mf and Mh defect in 19 unrelated families with GRTH, we applied separate polymerase chain reactions using allele-specific oligonucleotide primers containing the normal and each of the two mutant nucleotides at the 3'-position. A total of 24 affected subjects and 13 normal family members were studied. The mode of inheritance was dominant in 13 families, was unknown in 5 families, and was clearly recessive in 1 family in which only the consanguineous subjects were affected. Primers containing the substitutions specific for Mf and Mh amplified exons 7 and 8, respectively, only in affected members of each of the two index families. Primers containing the normal sequences amplified exons 7 and 8 of the TR beta gene in all subjects except affected members of one family. In this family with recessively inherited GRTH, neither exon could be amplified using any combinations of primers and DNA blot revealed absence of all coding exons. These results indicate a major deletion of the TR beta gene, including both DNA and hormone binding domains. Since heterozygous members of this family are not affected, the presence of a single normal allele is sufficient for normal function of the TR beta. These data also support the hypothesis that in the dominant mode of GRTH inheritance the presence of an abnormal TR beta interferes with the function of the normal TR beta. Distinct mutations are probably responsible for GRTH in unrelated families.
Alleles↗
The effect of hepatic enzyme-inducing drugs on thyroid hormones and the thyroid gland.
With the understanding that various drugs, industrial chemicals, and chemicals of environmental importance can increase thyroid hormone hepatic metabolism and excretion, it is important to consider whether compensation by the thyroid gland for this increased excretion can lead to stimulation of the hypothalamic-pituitary-thyroid axis and possibly secondary hyperplastic or neoplastic changes in the thyroid. The compounds discussed in this review all affect thyroid function by increasing biliary excretion of thyroid hormone metabolites. Numerous studies have been performed to elucidate the effect of these drugs on thyroid hormone equilibrium. Animals given PB compensate for the increased biliary excretion with an elevated TSH allowing maintenance of a euthyroid state. Human studies demonstrate increased thyroid hormone plasma clearance, but without an increased TSH. The effects of an experimental leukotriene antagonist are similar. In humans, diphenylhydantoin has been conclusively shown to cause a decrease in peripheral thyroid hormone levels, although without evident hypothyroidism or increase in TSH. Limited studies of rifampin and carbamazepine reveal similar results. Nicardipine in rats causes reproducible decreases in free T4 levels, although it does not clearly stimulate a rise in TSH levels. An experimental imidazole caused reversible lowering of peripheral thyroid hormone levels in rats; in this study TSH was not measured. Studies with aromatic hydrocarbons administered to rats reveal a general decrease in T4 levels, with a compensatory increase of TSH. The effects of chronic administration of a compound that can cause increased thyroid hormone metabolism with compensation via increased TSH production are of more than theoretical interest, as it has been well documented that constant stimulation of the thyroid gland in rats with supraphysiological levels of TSH causes goiter, thyroid hyperplasia, adenomas, and carcinomas. In humans with congenital metabolic thyroid deficiencies there is an increased incidence of thyroid neoplasia, suggesting an association with chronic increased TSH levels. In contrast, however, large epidemiological studies of areas of endemic goiter do not show an association of human thyroid cancer with iodine deficiency and presumed chronic thyroid gland stimulation. Histological evidence of thyroid follicular hyperplasia has been noted in rats after administration of phenobarbital, nicardipine, polycyclic hydrocarbons, and possibly an experimental imidazole. Increased thyroid gland size has been demonstrated in rats given phenobarbital, nicardipine, a leukotriene antagonist, and various polycyclic hydrocarbons. Thyroid carcinoma in rats has been associated with treatment with nicardipine and after exposure to several aromatic hydrocarbons.(ABSTRACT TRUNCATED AT 400 WORDS)
Animals↗
Effects of zinc and other divalent metals on deoxyribonucleic acid binding and hormone-binding activity of human alpha 1 thyroid hormone receptor expressed in Escherichia coli.
Full-length human thyroid hormone receptor alpha 1 (hTR alpha 1) was expressed in Escherichia coli using a T7 expression system. While present in large amounts, the receptor was highly enriched in the insoluble fraction after cell lysis. We describe here the successful solubilization and refolding of the expressed receptor in a functional form in the presence of Zn2+. Using a DNA-cellulose binding assay and gel shift assay, we found that treatment of expressed receptor with 1 mM EDTA in the denaturing agent (5 M guanidine-HCl) results in the formation of aporeceptor that does not specifically recognize target DNA, while it does retain T3-binding activity. This aporeceptor recovered DNA-binding activity by adding Zn2+ during refolding. Zinc-induced restoration of DNA-binding activity occurred in a dose- and time-dependent manner. Moreover, once recovered, this DNA-binding activity persisted without Zn2+, even in the presence of 1 mM EDTA. These data indicate that the hTR alpha 1 molecule has a high affinity for Zn2+, and this metal coordination is essential for proper folding of TR protein into its native active structure.
Base Sequence↗
Genetic linkage studies of thyroid peroxidase (TPO) gene in families with TPO deficiency.
We have conducted biochemical and genetic studies in five unrelated families (denoted A, C, R, P, and G), which included nine goitrous subjects (five borderline euthyroid and four hypothyroid) with complete (n = 6) or partial (n = 3) thyroid peroxidase (TPO) deficiency. Thyroid tissue was obtained from four subjects, respectively, in families A, C, and R. No iodide organification or iodide incorporation into protein was present in families A and C. The two affected siblings in family R had a low normal tissue thyroperoxidase activity. Using a 0.8-kilobase (kb) cDNA clone (pM5) encoding 30% of the cDNA of human TPO gene down-stream from basepair 730 and four restriction enzymes (TaqI, PstI, BglI, and BglII), we were unable to find any polymorphisms in family A. In another family (C) blood samples were obtained from only two family members, and consequently, it was not possible to determine linkage. DNA from families G, P, and C showed biallelic polymorphisms when digested with BglII, at 8.7 and 8.5 kb. In family R we detected two biallelic polymorphisms at 9.0 and 8.5 kb, and the 9.0-kb bands were clearly larger than 8.7-kb bands found in the other subjects. Also, there was an absence of a 4.0- to 3.9-kb band that may represent a partial gene deletion. With PstI-restricted DNA a possible deletion of 5.5-kb band was also present in affected siblings of family R. The logarithm of odds (Lod) score analyzed from the family with inbreeding (R) was compatible with linkage of disease and the TPO gene (Lod = 2.08). When this method was used with families G and P, the Lod score was inconsistent with linkage between disease and the TPO gene. These data suggest that the cause of TPO deficiency in these families is heterogeneous. However, the restriction fragment length polymorphism pattern of BglII-restricted DNA in the R family strongly suggests that a partial TPO gene deletion has occurred in this family.
Bacterial Proteins↗
Genetic factors in autoimmune thyroid disease analyzed by restriction fragment length polymorphisms of candidate genes.
Possible genetic effects on the development of autoimmune thyroid disease were studied by analysis of restriction fragment length polymorphisms (RFLPs) of candidate genes. Peripheral blood leukocyte DNA was obtained from 65 caucasian patients with Graves' disease, 63 caucasian patients with Hashimoto's thyroiditis, and 65 caucasian controls. RFLP analysis was carried out on genomic DNA, using probes for DR beta, DQ alpha, DQ beta, DP alpha, DP beta, T-cell receptor TCR alpha, and thyroid peroxidase. The methodology allowed HLA-DR and DQ typing and provided information on specific RFLP patterns related to T cell receptor (TCR)alpha, DP alpha and -beta, and -beta, and thyroid peroxidase. HLA-DR3 frequency was significantly increased in patients with Graves' disease, as reported previously by others, but neither DNA-derived subtype of DR3 was differentially increased. HLA-DQw2 was also present in increased frequency because of its linkage disequilibrium with HLA-DR3. It is uncertain whether the primary susceptibility is with DQ, DR, or another nearby locus. Susceptibility was not related in these studies to genetic loci recognized in these studies involving DQ alpha, DP, TCR, or thyroid peroxidase. A significant linkage disequilibrium between DR3 and a specific DX alpha RFLP was observed in Graves' disease, but is believed to be representative of a generalized linkage disequilibrium between DR3 and DX alpha, rather than a specific abnormality in Graves' disease. Previous studies indicating association with specific TCR RFLPs could not be reproduced. The relative risk for carriers of HLA-DR3 subtype A in this study was 7.37-fold. RFLP analysis offers the possibility of investigating linkage in a variety of candidate genes as well as established genetic relationships for potentially important subtypes. While the significant relationship with HLA-DR3/DQw2 was reconfirmed, the involvement of other genes or haplotypes could not be established.
DNA↗
Second operations for "completion" of thyroidectomy in treatment of differentiated thyroid cancer.
The role of elective completion thyroidectomy after lobectomy for differentiated thyroid cancers remains controversial. The potential benefit of tumor removal by the second procedure is considered by some to be overbalanced by a prohibitive operative morbidity rate. During a 20-year period at the University of Chicago Medical Center, 26 patients underwent completion thyroidectomy within a 6-month period of the original thyroid operation. This group represents 8% of the 326 patients who underwent surgery during that time for differentiated thyroid cancer (269 papillary and 57 follicular). Of the 26 patients, 18 had papillary and eight had follicular cancers. The average size was 2.5 cm, with 24 of 26 being greater than 1 cm in diameter. At the first operation, 81% of tumors were intrathyroidal. Eight percent had lymph node metastases and 12% manifested local invasion. Tumor was found in eight (31%) of 26 of the reoperative specimens. The incidence of tumor did not vary by histologic type but did differ according to the extent of the original operation. Cancer was found in 50% (three of six) of those who had undergone previous partial lobectomy, in 33% (five of 15) of those after a total lobectomy, and in none of five who had undergone a prior bilateral (although incomplete) thyroid resection. One permanent recurrent nerve injury occurred at the first operation. No additional recurrent nerve injuries or hypoparathyroidism occurred as a result of the second operation. Finally, no disease characteristic of the initial tumor (e.g., size, clinical class, tumor capsular invasion, multifocality, thyroiditis, or extrathyroidal tumor invasiveness) predicted the presence or absence of tumor on the second side. We conclude that completion thyroidectomy is appropriate for patients with lesions 1 cm or greater who have undergone lobectomy or less at the original operation, because 40% of such patients would be expected to have residual cancer. With care, this operation can be performed with minimal morbidity.
Adenocarcinoma↗
The roles of three forms of human thyroid hormone receptor in gene regulation.
We have expressed three forms of human thyroid hormone receptor (hTR alpha 1, alpha 2, and beta) in cultured cells by transient transfection. hTR alpha 1 and beta transfected cells showed increased triiodothyronine (T3) binding capacity, but hTR alpha 2 transfected cells did not. When hTR alpha 1 or beta was cotransfected with pUrGH(S), in which a portion of the rat GH 5' flanking region (-236/-147) was ligated into the CAT reporter plasmid (pUTKAT1), T3 increased CAT gene expression. When hTR alpha 2 was cotransfected with pUrGH(S), T3 did not alter CAT gene expression. When hTR alpha 1 or beta was cotransfected with pUrGH(O), in which a synthetic oligonucleotide representing the TRE from the rat GH 5' flanking region (-189/-160) was substituted for the natural enhancer in pUTKAT1, T3 increased CAT gene expression. When hTR alpha 1 and beta were cotransfected with pUrGH(O), induction by T3 was increased. When hTR alpha 2 was cotransfected with hTR alpha 1 or beta, induction by T3 was decreased. These results indicate that hTR alpha 1 and beta function as native TR, that hTR alpha 1 and beta can recognize the same TRE, that hTR alpha 1 and beta can function additively, and that hTR alpha 2 can inhibit the action of hTR alpha 1 and beta.
Animals↗
Structural analysis of human thyroid hormone receptor beta gene.
Thyroid hormone receptors (TR) are ligand-dependent, DNA-binding, trans-acting transcriptional factors belonging to the erbA-related steroid/thyroid hormone receptor superfamily. To better understand the structural and functional characteristics of TRs, we isolated the gene encoding human TR beta 1 (hTR beta 1). The coding region of hTR beta 1 is split into at least eight exons. Each exon well correlates with functional domains of hTR beta 1 protein, and the exon/intron organization is highly conserved when compared with the chicken c-erbA gene which encodes an alpha-type chicken TR. We demonstrate that hTR beta has at least two mRNA forms having different lengths of the 3' untranslated region. We also note several nucleotide corrections of hTR beta 1 cDNA sequence.
Animals↗
Expression of HLA ABC and DR antigens in thyroid neoplasia and correlation with mononuclear leukocyte infiltration.
The rejection of tumor cells by the immune system depends on the production of tumor-associated antigens and the expression of HLA antigens on these cells. We therefore studied the expression of HLA ABC and DR antigens in malignant and benign thyroid disorders and correlated it with the types and extent of mononuclear cell infiltration. In the normal thyroid, HLA ABC expression was weak and focal, while it was diffusely present in benign disorders and in most but not all malignancies. HLA DR antigens, while absent or infrequently expressed in normal thyroid, were strongly but often focally expressed in all cases of autoimmune thyroid disease (AITD), as well as in most cases of malignant tumors and benign epithelium surrounding these tumors, and colloid nodule disease. There was a T cell predominance in all disorders, and the CD4+/CD8+ ratio was greater than 1 in most benign and malignant specimens. There was a direct correlation between the high expression of HLA antigens and dense inflammatory infiltration in AITD but not in most tumor specimens. Lack of such correlation suggests that the expression of HLA antigens is an autonomous event in tumors, independent of cellular infiltrate.
Antibodies, Monoclonal↗
Comparison of RA 131I treatment protocols for Graves' disease.
The efficacy of 131I therapy in achieving euthyroidism has been studied in a group of 264 patients followed for up to 10 yr. One hundred and eighty-six were given a dose adjusted for thyroid size and radioactive iodine uptake (Protocol 1), and a second group received the same dosage followed by antithyroid drug therapy plus potassium iodide for 15 days (Protocol 2). At 10-yr follow-up, 50-60% of patients were euthyroid. 25-29% of patients required 2 doses of 131I, and 4-5% required 3 doses. Fewer patients became hypothyroid when their pretreatment FTI was above the average value. More patients became hypothyroid, if their pretreatment test for antimicrosomal antibodies was positive. Patients who required a second dose of radioactive iodide had a significantly greater chance of having worsening of their ophthalmopathy than those who became hypothyroid after the first dose. Treatment with radioactive iodide under either protocol appears to achieve euthyroidism at 10 yr with an incidence higher than that achieved by antithyroid drugs and comparable to that reported for subtotal thyroidectomy.
Combined Modality Therapy↗
Characterization of site-specific polyclonal antibodies to c-erbA peptides recognizing human thyroid hormone receptors alpha 1, alpha 2, and beta and native 3,5,3'-triiodothyronine receptor, and study of tissue distribution of the antigen.
The translated products of v-erbA-related cDNAs have been demonstrated to be thyroid hormone receptors, and three different forms of receptor (alpha 1, alpha 2, and beta) have been found in human tissues. We synthesized five peptides corresponding to different portions of these three receptors and raised site-specific polyclonal-antipeptide sera in rabbits. Each antibody displayed high titer and specificity for its respective antigen when tested in an enzyme-linked immunosorbent assay. Each immunoprecipitated the corresponding in vitro translated products of human c-erbA alpha 1, alpha 2, or beta. Two of the antisera were specific for beta, one for alpha 2, and one detected a sequence common to alpha 1 and alpha 2. The fifth was directed toward the DNA-binding area of the proteins and interacted with each receptor. The four antibodies against alpha 1 and beta immunoprecipitated the native thyroid hormone receptor from rat liver and caused a partial shift in the elution profile of the native receptor labeled with [125I]T3 on Sephacryl S-300 column chromatography. The antibody against alpha 2 protein did not interact with native thyroid hormone receptor from rat liver. Using the indirect immunofluorescence technique with the five antibodies, we detected immunoreactivity primarily in the nucleus of cells in several tissues. In general, there was coordinate expression of both alpha and beta receptors in each organ examined, in agreement with previous data on tissue distribution of mRNAs for human thyroid hormone receptors. These studies prove the identity of v-erbA-related gene products with native thyroid hormone receptors and the expression of both alpha and beta receptors in nuclei of human and rat tissues.
Animals↗
The regulatory role of human helper T-cell clones on antithyroid antibody production by peripheral B-cells.
The helper effects of thyroid antigen-specific T-cell clones (TCC) on antibody production by peripheral B-cells were studied and compared with similar effects of self major histocompatibility complex II (MHC-II)-reactive TCC as well as uncloned CD4+ cells. Ten TCC were derived from thyroid tissue or peripheral blood mononuclear cells (PBMC) in patients with Graves' disease. Uncloned CD4+ cells were also obtained from PBMC in patients with autoimmune thyroid disease. All TCC were CD3+/CD4+. B-Cells from patients with mainly high serum levels of microsomal antibodies (McAb) were cultured alone and with either TCC or uncloned CD4+ cells in the presence or absence of thyroid antigens [microsomal antigen/thyroid peroxidase (McAg/TPO) and thyroglobulin (Tg)] or pokeweed mitogen (PWM). Total immunoglobulin G (IgG) and specific thyroid antibodies were measured by enzyme-linked immunosorbent assay. Self MHC-II-reactive TCC induced B-cell production of total IgG and even McAb independent of antigens or PWM. Specific TCC required thyroid antigens to induce antibodies. The optimal McAg/TPO or Tg concentration was 10 ng/mL for total IgG production and 1 ng/mL McAg/TPO for McAb synthesis. The addition of PWM did not affect McAb production, but enhanced total IgG synthesis by B-cells under the influence of some specific TCC. Uncloned CD4+ cells induced both total IgG and McAb synthesis in the presence of PWM. With thyroid antigens, uncloned CD4+ cells induced total IgG synthesis at levels comparable to those of specific TCC, but induced smaller quantities of McAb in the presence of McAg/TPO. Our antigen-specific TCC could, therefore, stimulate specific B-cells to produce thyroid antibodies in vitro. Self MHC-II-reactive TCC could also induce specific antibodies by B-cells. Both self MHC-II-reactive CD4+ cells and antigen-specific CD4 cells may play an important role in the pathogenesis and/or perpetuation of autoimmune thyroid disease.
Antibodies↗
Natural history, treatment, and course of papillary thyroid carcinoma.
We have analyzed the course of papillary thyroid carcinoma in 269 patients managed at the University of Chicago, with an average follow-up period of 12 yr from the time of diagnosis. Patients were categorized by clinical class; I, with intrathyroidal disease; II, with cervical nodal metastases; III, with extrathyroidal invasion; and IV, with distant metastases. Half of the patients had a history of thyroid enlargement known, on the average, for over 3 yr. In 15% of patients given thyroid hormone, the mass decreased in size. The peak incidence of cancer was when subjects were between 20-40 yr of age. Tumors averaged 2.4 cm in size; 21.6% had tumor capsule invasion, and 46% of patients had multifocal tumors. Sixty-six percent of the patients had near-total or total thyroidectomy. The overall incidence of postoperative hypoparathyroidism was 8.4%, but the incidence was zero in 83 near-total or total thyroidectomies carried out by 1 surgeon. Twenty-five percent of the patients had continuing or recurrent disease, and 8.2% died from cancer. Deaths occurred largely in patients with class III or IV disease. Cervical lymph nodes were associated with increased recurrences, but not increased deaths. Extrathyroidal invasion carried an increased risk of 5.8-fold for death, and distant metastases increased this risk 47-fold. Age over 45 yr at diagnosis increased the risk of death 32-fold. Tumor size over 3 cm increased the risk of death 5.8-fold. Surgical treatment combining lobectomy plus at least contralateral subtotal thyroidectomy was associated, by Cox proportional hazard analysis, with decreased risk of death in patients with tumors larger than 1 cm and decreased risk of recurrence among all patients, including patients in classes I and II, compared to patients who underwent unilateral thyroid surgery or bilateral subtotal resections. By chi 2 analysis, 131I ablation of residual thyroid tissue after operation was associated with decreased risk of recurrence in tumors larger than 1 cm and decreased risk of death in patients in classes I and II with tumors more than 1 cm in size. The data strongly support the use of more extensive initial surgery in class I and II patients with tumors more than 1 cm in size as well as postoperative radioactive 131I ablation of thyroid remnant tissue.
Age Factors↗
A human early response gene homologous to murine nur77 and rat NGFI-B, and related to the nuclear receptor superfamily.
When a human fetal muscle cDNA library was screened with the human thyroid hormone receptor alpha 2 cDNA at low stringency, we found a weakly hybridizing cDNA. The sequence of the insert was 2498 basepairs, with an open reading frame of 1794 basepairs encoding a protein of 598 amino acids and a predicted molecular mass of 64 kDa. The DNA-binding domain and the ligand-binding domain are similar to those of steroid and thyroid hormone receptors. Moreover, this cDNA is highly homologous to mouse nur77 and rat NGFI-B, which are early response genes induced by nerve growth factor and other serum growth factors. We designated this gene NAK1. The modulation of expression of NAK1 during stimulation of cell growth was studied. The mRNA of NAK1 was induced rapidly and transiently by growth-stimulating agents, such as adenosine diphosphate, in monkey kidney cells (BSC-1), by phytohemagglutinin in human lymphocytes, and by serum stimulation of arrested fibroblasts. It is expressed in human fetal muscle and adult liver, brain, and thyroid. NAK1 could be a nuclear receptor. It will be of great interest to determine the ligand for NAK1 and the genes that are regulated by it.
Amino Acid Sequence↗
Dominant negative transcriptional regulation by a mutant thyroid hormone receptor-beta in a family with generalized resistance to thyroid hormone.
An abnormal human thyroid hormone beta-receptor (hTR beta-Mf), which has a glycine to arginine substitution in the hormone-binding domain, has been identified in affected members of one family with generalized resistance to thyroid hormone. To better understand the mechanism by which this mutation produces the observed abnormality, expression vectors for the wild-type and mutant thyroid hormone receptors (TRs) were prepared to test hormone-binding activity and trans-activation function. Nuclear extracts of COS-7 cells transfected with wild-type TRs showed specific T3-binding activity, while mutant receptor-transfected COS-7 nuclear extract failed to bind T3. On the other hand, in a avidin-biotin complex DNA-binding assay, in vitro translated hTR beta-Mf showed high binding activity to the thyroid hormone response element, which was indistinguishable from that of wild-type TRs. In a transient expression study, only the wild-type TRs activated a rat GH gene promoter-chloramphenicol acetyltransferase fusion gene in a T3-dependent manner. Additionally, when wild-type TR and hTR beta-Mf were cotransfected, hTR beta-Mf inhibited gene activation regulated by wild-type TRs. From these results we conclude that 1) hTR beta-Mf has no demonstrable T3 binding and appears to have minimal, if any, ability to activate a thyroid hormone-responsive gene in spite of its preserved ability to bind to a TRE in DNA; 2) hTR beta-Mf inhibits the transcriptional activation of a thyroid hormone-responsive gene by the wild-type TRs in a dominant manner; and 3) the dominant negative regulatory function of hTR beta-Mf appears to explain the clinical manifestations of thyroid hormone resistance produced by this mutation when present in the heterozygous state.
Animals↗
What controls thyroid growth--that is, thyroid size?
Explore the source record for details and available documents.
Adrenal Glands↗
The molecular basis of thyroid hormone action.
Explore the source record for details and available documents.
Amino Acid Sequence↗