Thyroid Hormone Receptor Beta Research Articles

Patients with mutations of the Thyroid hormone beta-receptor show an ADHD-like phenotype for performance monitoring: an electrophysiological study.

Resistance to thyroid hormone beta (RTHβ) is a syndrome of reduced responsiveness of peripheral tissue to thyroid hormone, caused by mutations in the thyroid hormone receptor beta (THRB). Its cognitive phenotype has been reported to be similar to attention deficit hyperactivity disorder (ADHD). This study used electrophysiological biomarkers of performance monitoring in RTHβ to contribute further evidence on its phenotypical similarity to ADHD. Twenty-one participants with RTHβ aged 18-67 years and 21 matched healthy controls performed a modified flanker task during EEG recording. The RTHβ and control groups were compared on behavioural measures and components of event related potentials (ERPs), i.e. the error related negativity (ERN), the error positivity (Pe) and P3 component. There were no significant group differences with regard to behaviour. RTHβ subjects displayed significantly reduced ERN and Pe amplitudes compared to the controls in the response-locked ERPs. In addition, we observed reduced P3 amplitudes in both congruent and incongruent trials, as well as prolonged P3 latencies in RTHβ subjects in the stimulus-locked ERPs. Our findings reveal alterations in error detection and performance monitoring of RTHβ patients, likely indicating reduced error awareness. The electrophysiological phenotype of RTHß subjects with regard to action monitoring is indistinguishable from ADHD.

Structural changes in thyroid hormone receptor-beta by T3 binding and L330S mutational interactions

The point mutations like L330S in the ligand binding domain (LBD) of thyroid hormone receptor-beta (THR-β) make the structural changes as reflected by Ramachandran plots, solvent accessible surface area, radial distribution functions, root mean square deviations and fluctuations, and interaction and internal energies of the LBD residues. By using nanoscale molecular dynamics (NAMD) simulations, the structural features of T3 liganded, unliganded and mutated THR-β LBD are compared to explore the molecular insights in euthyroid, hypothyroid and resistance to thyroid hormones (RTH) states, respectively. The L330S-mutant causes steric hindrance while binding T3 into THR-β LBD causing RTH in the thyroid patients.

The Thyroid Hormone Receptor-RUNX2 Axis: A Novel Tumor Suppressive Pathway in Breast Cancer.

Metastatic breast cancer is refractory to conventional therapies and isan end-stage disease. RUNX2 is a transcription factor that becomes oncogenic when aberrantly expressed in multiple tumor types, including breast cancer, supporting tumor progression and metastases. Our previous work demonstrated that the thyroid hormone receptor beta (TRβ) inhibits RUNX2 expression and tumorigenic characteristics in thyroid cells. As TRβ is a tumor suppressor, we investigated the compelling question whether TRβ also regulates RUNX2 in breast cancer. The Cancer Genome Atlas indicates that TRβ expression is decreased in the most aggressive basal-like subtype of breast cancer. We established that modulated levels of TRβ results in corresponding changes in the high levels of RUNX2 expression in metastatic, basal-like breast cells. The MDA-MB-231 triple-negative breast cancer cell line exhibits low expression of TRβ and high levels of RUNX2. Increased expression of TRβ decreased RUNX2 levels. The thyroid hormone-mediated suppression of RUNX2 is TRβ specific as TRα overexpression failed to alter RUNX2 expression. Consistent with these findings, knockdown of TRβ in non-tumor MCF10A mammary epithelial-like cells results in an increase in RUNX2 and RUNX2 target genes. Mechanistically, TRβ directly interacts with the proximal promoter of RUNX2 through a thyroid hormone response element to reduce promoter activity. The TRβ suppression of the oncogene RUNX2 is a signaling pathway shared by thyroid and breast cancers. Our findings provide a novel mechanism for TRβ-mediated tumor suppression in breast cancers. This pathway may be common to many solid tumors and impact treatment for metastatic cancers.

An Investigational Agent for the Treatment of Nonalcoholic Steatohepatitis

Resmetirom (MGL-3196) is an oral, liver-directed, selective thyroid hormone receptor beta agonist. It regulates metabolic pathways in the liver that

Acute microcystin-LR exposure interfere thyroid hormones homeostasis in adult zebrafish (Danio rerio).

Microcystin-LR (MC-LR) in the aquatic environment may disturb thyroid hormone (TH) homeostasis. It is not clear how MC-LR affects downstream biological processes after TH disturbance. After exposure to 50, 100, 200 and 400 μg/L MC-LR for 24, 48, 72, or 96 h, alterations of the TH metabolism of adult zebrafish at thyroxine (T4), triiodothyronine (T3) levels, and iodothyronine deiodinase (Dio) activity, were observed. After exposure to MC-LR at 400 μg/L, T3 and T4 levels decreased significantly in females (p < 0.05) and returned to normal levels at 96 h. In males, T4 levels were not significantly different between groups. The expression of corticotropin releasing hormone, thyroid-stimulating hormone beta subunit, transthyretin, sodium/iodide cotransporter, thrombopoietin, thyroid hormone receptor alpha and beta changed, but not in a dose-dependent manner. Acute MC-LR exposure induced a negative feedback regulation of the hypothalamic-pituitary-thyroid axis in adult zebrafish, and females were more sensitive than males. In conclusion, acute MC-LR exposure disrupted the TH metabolism by altering Dio activity and gene expression of the HPT axis; these changes may affect the complement system through regulation of c9 mRNA synthesis.

Revealing a Mutant-Induced Receptor Allosteric Mechanism for the Thyroid Hormone Resistance.

SummaryResistance to thyroid hormone (RTH) is a clinical disorder without specific and effective therapeutic strategy, partly due to the lack of structural mechanisms for the defective ligand binding by mutated thyroid hormone receptors (THRs). We herein uncovered the prescription drug roxadustat as a novel THRβ-selective ligand with therapeutic potentials in treating RTH, thereby providing a small molecule tool enabling the first probe into the structural mechanisms of RTH. Despite a wide distribution of the receptor mutation sites, different THRβ mutants induce allosteric conformational modulation on the same His435 residue, which disrupts a critical hydrogen bond required for the binding of thyroid hormones. Interestingly, roxadustat retains hydrophobic interactions with THRβ via its unique phenyl extension, enabling the rescue of the activity of the THRβ mutants. Our study thus reveals a critical receptor allosterism mechanism for RTH by mutant THRβ, providing a new and viable therapeutic strategy for the treatment of RTH.

Skeletal effects of nongenomic thyroid hormone receptor beta signaling.

Thyroid hormone (TH) levels increase rapidly during the prepubertal growth period in mice, and this change is necessary for endochondral ossification of the epiphyses. This effect of TH on epiphyseal chondrocyte hypertrophy is mediated via TRβ1. In addition to its traditional genomic signaling role as a transcription factor, TRβ1 can also exert nongenomic effects by interacting with other signaling molecules such as PI3K. To investigate the role of nongenomic TRβ1 signaling in endochondral ossification, we evaluated the skeletal phenotype of TRβ147F mutant mice which exhibit a normal genomic response of TRβ1 to TH, but the nongenomic response through the PI3K pathway is impaired. Using microCT, we found that 13-week-old TRβ147F mice had significantly less trabecular bone mass at three sites. Histomorphometric analyses revealed that mineralizing surface to bone surface and BFR/BS were reduced in the mutant mice. Mechanistically, we found that activation of TRβ increased Alp and Osx expression in control but not TRβ147F osteoblasts. Since canonical β-catenin signaling has been implicated in mediating nongenomic TRβ-PI3K signaling, we evaluated the effect of TRβ1 activation on β-catenin target gene expression in MC3T3-E1 pre-osteoblasts. We found that β-catenin target genes were increased, suggesting that nongenomic TRβ1-PI3K pathway modulation of β-catenin signaling may mediate TRβ1 effects on osteoblast differentiation. Together, these results suggest that TH acting through TRβ1 regulates endochondral ossification in part via nongenomic signaling in mice. Further investigation of this nongenomic mechanism of TRβ1 signaling could lead to novel therapeutic targets for treatment and prevention of osteoporosis.

Thyroid Hormone Receptor Alpha Is Required for Thyroid Hormone-Dependent Neural Cell Proliferation During Tadpole Metamorphosis.

Thyroid hormone (T3) plays several key roles in development of the nervous system in vertebrates, controlling diverse processes such as neurogenesis, cell migration, apoptosis, differentiation, and maturation. In anuran amphibians, the hormone exerts its actions on the tadpole brain during metamorphosis, a developmental period dependent on T3. Thyroid hormone regulates gene transcription by binding to two nuclear receptors, TRα and TRβ. Our previous findings using pharmacological and other approaches supported that TRα plays a pivotal role in mediating T3 actions on neural cell proliferation in Xenopus tadpole brain. Here we used Xenopus tropicalis (X. tropicalis) tadpoles with an inactivating mutation in the gene that encodes TRα to investigate roles for TRα in mitosis and gene regulation in tadpole brain. Gross morphological analysis showed that mutant tadpoles had proportionally smaller brains, corrected for body size, compared with wildtype, both during prometamorphosis and at the completion of metamorphosis. This was reflected in a large reduction in phosphorylated histone 3 (pH3; a mitosis marker) immunoreactive (ir) nuclei in prometamorphic tadpole brain, when T3-dependent cell proliferation is maximal. Treatment of wild type premetamorphic tadpoles with T3 for 48 h induced gross morphological changes in the brain, and strongly increased pH3-ir, but had no effect in mutant tadpoles. Thyroid hormone induction of the direct TR target genes thrb, klf9, and thibz was dysregulated in mutant tadpoles. Analysis of gene expression by RNA sequencing in the brain of premetamorphic tadpoles treated with or without T3 for 16 h showed that the TRα accounts for 95% of the gene regulation responses to T3.

Lineage tracing analysis of cone photoreceptor associated cis-regulatory elements in the developing chicken retina

During vertebrate retinal development, transient populations of retinal progenitor cells with restricted cell fate choices are formed. One of these progenitor populations expresses the Thrb gene and can be identified by activity of the ThrbCRM1 cis-regulatory element. Short-term assays have concluded that these cells preferentially generate cone photoreceptors and horizontal cells, however developmental timing has precluded an extensive cell type characterization of their progeny. Here we describe the development and validation of a recombinase-based lineage tracing system for the chicken embryo to further characterize the lineage of these cells. The ThrbCRM1 element was found to preferentially form photoreceptors and horizontal cells, as well as a small number of retinal ganglion cells. The photoreceptor cell progeny are exclusively cone photoreceptors and not rod photoreceptors, confirming that ThrbCRM1 progenitor cells are restricted from the rod fate. In addition, specific subtypes of horizontal cells and retinal ganglion cells were overrepresented, suggesting that ThrbCRM1 progenitor cells are not only restricted for cell type, but for cell subtype as well.

Evolutionary Conservation of Thyroid Hormone Receptor and Deiodinase Expression Dynamics in ovo in a Direct-Developing Frog, Eleutherodactylus coqui.

Direct development is a reproductive mode in amphibians that has evolved independently from the ancestral biphasic life history in at least a dozen anuran lineages. Most direct-developing frogs, including the Puerto Rican coquí, Eleutherodactylus coqui, lack a free-living aquatic larva and instead hatch from terrestrial eggs as miniature adults. Their embryonic development includes the transient formation of many larval-specific features and the formation of adult-specific features that typically form postembryonically—during metamorphosis—in indirect-developing frogs. We found that pre-hatching developmental patterns of thyroid hormone receptors alpha (thra) and beta (thrb) and deiodinases type II (dio2) and type III (dio3) mRNAs in E. coqui limb and tail are conserved relative to those seen during metamorphosis in indirect-developing frogs. Additionally, thra, thrb, and dio2 mRNAs are expressed in the limb before formation of the embryonic thyroid gland. Liquid-chromatography mass-spectrometry revealed that maternally derived thyroid hormone is present throughout early embryogenesis, including stages of digit formation that occur prior to the increase in embryonically produced thyroid hormone. Eleutherodactylus coqui embryos take up much less 3,5,3′-triiodothyronine (T3) from the environment compared with X. tropicalis tadpoles. However, E. coqui tissue explants mount robust and direct gene expression responses to exogenous T3 similar to those seen in metamorphosing species. The presence of key components of the thyroid axis in the limb and the ability of limb tissue to respond to T3 suggest that thyroid hormone-mediated limb development may begin prior to thyroid gland formation. Thyroid hormone-dependent limb development and tail resorption characteristic of metamorphosis in indirect-developing anurans are evolutionarily conserved, but they occur instead in ovo in E. coqui.

Reduced Sensitivity to Thyroid Hormone as a Transgenerational Epigenetic Marker Transmitted Along the Human Male Line

Background: Evidence for transgenerational epigenetic inheritance in humans is still controversial, given the requirement to demonstrate persistence of the phenotype across three generations. A previous study showed that exposure of human and mouse embryos to high maternal thyroid hormone (TH) concentrations not only affects the newborns but also subsequently reduces thyrotroph sensitivity to TH during adult life. The current investigation set out to determine if this epigenetic effect is transmitted by humans not exposed in utero to high TH levels to their offspring. Methods: The study took advantage of the high frequency of intrauterine exposure to high TH in the Azorean wild-type population born to healthy mothers with high TH levels because of a heterozygous TH receptor beta gene mutation. Wild-type individuals from F2 (second) and F3 (third) generations were studied, whose parents and grandparents, respectively, were not exposed to high maternal TH levels. Twenty-six individuals belonging to 17 nuclear families were tested for their sensitivity to TH using their thyrotropin (TSH) response to thyrotropin-releasing hormone (TRH) after administration of liothyronine (LT3). Results: Preservation of reduced sensitivity to TH (RSTH) was found in descendants of males but not of females with likewise RSTH. In F2, offspring of fathers but not of mothers exposed to high TH levels had RSTH (TRH-stimulated TSH of 6.39 ± 0.63 vs 1.58 ± 0.41 mIU/L [p < 0.001], respectively, after treatment with LT3). In F3, whose parents nor themselves were exposed to TH excess during their fetal life, descendants of fathers and not mothers had RSTH (TRH-stimulated TSH of 4.60 ± 0.61 vs 1.37 ± 0.23 mIU/L [p < 0.01], respectively, after pretreatment with LT3). Conclusions: Since intrauterine total body and gonadal exposure to elevated TH can potentially affect only the F1 and F2, respectively, the results obtained from F3 confirm a true inheritance of an epigenetic effect, scarcely observed in humans. While the exact mechanism underlying the inheritance of this epigenetic effect remains unknown, it correlates with type 3 deiodinase overexpression demonstrated in pituitary glands of mice born to dams with high TH. This enzyme inactivates TH, and is encoded by an imprinted gene with specific parent of origin expression.

SAT-573 Characterization of the Gene Expression Program of a Mutant Thyroid Hormone Receptor in Anaplastic Thyroid Cancer

Thyroid cancer is the most commonly diagnosed endocrine malignancy. Although survival rates for the majority of thyroid cancer subtypes are high compared to other cancers, the de-differentiated anaplastic thyroid cancer (ATC) is particularly aggressive, with a median survival time of less than 6 months. Intriguingly, thyroid hormone receptor beta (TRβ) has been demonstrated to repress tumor growth in thyroid cancer models, but the mechanism is not well established. Additionally, phosphorylation of a tyrosine residue (Y406) is critical for the tumor suppressive phenotype of TRβ; mutation of this residue ablates TRβ-mediated tumor suppression (1). We hypothesized that the signaling mediated by wild type, but not Y406 TRβ defines the critical pathways for tumor suppression. We restored WT or Y406F TRβ expression by lentiviral transduction in an authenticated ATC cell line, SW1736. WT TRβ decreased cell proliferation, an effect amplified by T3. Y406F did not significantly reduce ATC cell proliferation and addition of T3 did not restore the antiproliferative effect implicating differential signaling. As we have previously identified TRβ suppression of the oncogene RUNX2 in thyroid cells (2), we determined the impact of Y406F TRβ on this signaling pathway. While Y406F TRβ reduced RUNX2 expression, the effect was less pronounced than noted with WT. Of importance, we previously demonstrated that the chromatin ATPase BRG1 cooperates with TRβ to reduce RUNX2 levels (3). Mutation of TRβ at Y406 eliminated this synergy. Finally, we determined the ligand-dependent and independent transcriptomes of WT and Y406F TRβ by RNA-sequencing. Critically, WT and Y406F TRβ both responded to T3 treatment, but exhibit different transcriptional profiles. Importantly, we were able to identify several tumor suppressor genes and putative tumor suppressor genes that were upregulated only in the WT-T3 treated cells including BRCA2, CHD1, and SEPT7. Utilizing Ingenuity Pathway Analysis, we determined repression of the epigenetic regulator KDM5B (a putative oncogene) and upregulation of CD24 activity (low in CD44+/CD24- cancer stem cells). These results define the TRβ transcriptome in aggressive thyroid cancer cells and reveal novel signaling in ATC. 1. Park JW, Zhao L, Webb P, Cheng S-y. Src-dependent phosphorylation at Y406 on the thyroid hormone receptor β confers the tumor suppressor activity. Oncotarget 2014;5:10002-16 2. Carr FE, Tai PW, Barnum MS, Gillis NE, Evans KG, Taber TH, et al. Thyroid Hormone Receptor-beta (TRbeta) Mediates Runt-Related Transcription Factor 2 (Runx2) Expression in Thyroid Cancer Cells: A Novel Signaling Pathway in Thyroid Cancer. Endocrinology 2016;157:3278-92 3. Gillis NE, Taber TH, Bolf EL, Beaudet CM, Tomczak JA, White JH, et al. Thyroid Hormone Receptor beta Suppression of RUNX2 is Mediated by Brahma Related Gene 1 Dependent Chromatin Remodeling. Endocrinology 2018

SUN-594 Skeletal Dysplasia and Growth Failure in Congenital Hypothyroidism Due to a Novel Form of Generalized Thyroid Hormone Resistance

Background: Thyroid hormone exerts systemic actions mediated by its specific receptors. These actions encompass a wide array of functions, including energy homeostasis, skeletal growth, neural development, cardiac function, and gastrointestinal function. There are two thyroid hormone receptors, thyroid hormone receptor alpha (THRA) and thyroid hormone receptor beta (THRB) which are encoded by genes on two different chromosomes and with differing tissue distributions. Only mutations in THRB were known until recently with a reported incidence of 1 in ~40,000. Mutations in thyroid receptor THRA have recently been discovered and are exceedingly rare, with 14 cases documented in the past five years. We report a case of a patient with generalized thyroid hormone resistance due to THRA mutation. Clinical Case: Patient was born to non-consanguineous parents at term and was appropriate for gestational age. Prenatal ultrasound was suspect for shortened long bones. Congenital heart disease (ASD and VSD) were detected at birth. Genetics consultation confirmed ultrasound concern with finding of mild rhizomelia. Patient had coarse facial features, macroglossia, and dysmorphic appearance. Initial genetics work-up showed normal chromosomes, normal newborn screening, and normal metabolic studies. Genetics was concerned for possible mucopolysaccharidosis, but further testing ordered did not confirm this diagnosis. Patient exhibited post-natal growth failure after birth with length well below 3rd percentile by 18 months old. Delayed developmental milestones (verbal > motor) were noted. Thyroid function tests between birth and 11 months old were normal. Thyroid function testing at 11 months old were suspect for central hypothyroidism with free T4 0.6 ng/dl (0.6-1.3) and TSH 1.07 uIU/ml (0.71-5.81). Cranial MRI scan showed no abnormalities in hypothalamic-pituitary area. Levothyroxine 37.5 mcg was started, and thyroid function tests normalized. However, little change was seen clinically in patient’s growth pattern or development. Whole exome screening performed in 2013 demonstrated a heterozygous mutation in the THRA gene consistent with generalized thyroid hormone resistance from this mutation. Liothyronine treatment was added in 2014. Growth has continued to be extremely slow with current height standard deviation score of -4.2. Patient is developmentally delayed and non-verbal. Conclusions: A constellation of findings including post-natal growth failure, skeletal findings, and prominent verbal developmental delays are seen in generalized thyroid hormone resistance due to THRA mutation. The subtle presentation of this condition is different from congenital hypothyroidism or generalized thyroid hormone resistance due to THRB mutation. Presentation of this case will hopefully help pediatric specialist to recognize and test for this condition more promptly.

SUN-545 A Rare Case of Resistance to Thyroid Hormone Due to Novel Mutation in THRB Gene Mistreated as Hyperthyroidism

Background: Resistance to thyroid hormone (RTH) is an inherited syndrome characterized by reduced responsiveness of target tissues to thyroid hormone. Incidence rate is about 1/40,000 live births [1]. RTH is due to defect in the thyroid hormone receptor, most common is being beta gene (THRB). It is not unusual to be confused with hyperthyroidism. We present a case of RTH with novel mutation which was wrongly managed by primary care provider (PCP) as hyperthyroidism. Case Presentation: 42 year old female was referred to Endocrine clinic by PCP for hyperthyroidism and thyroid nodule. She was initially presented to PCP with lethargy, constipation and neck pain. Ultrasound neck showed left thyroid nodule of 2 cm and lab tests showed TSH 3.14 uIU/ml (0.3-4.0), free T4 3.6 ng/dl (0.9-1.7) and free T3 5.3 pg/ml (2.1-4.4). She was started on Methimazole and propranolol. She had FNA of left thyroid nodule and was benign cytology. She stopped Methimazole after few months due to extreme lethargy and weight gain. Careful history in endocrine clinic explored that her mother had thyroid cancer, was evaluated in National Institute of Health (NIH) for abnormal thyroid hormones and was diagnosed with thyroid hormone resistance. Further testing on family revealed that she also had similar problem. She used to take cytomel several years ago and later stopped due to tachycardia. She had intermittent fatigue, constipation and palpitations. She had regular menstrual cycles, stable weight and no heat or cold intolerance. Pulse was 95 bpm. She had normal size thyroid gland, normal deep tendon reflexes and no tremors. Repeat lab tests showed TSH 4.60 uIU/ml (0.36-3.74), free T4 2.33 ng/dl (0.76-1.46), free T3 7.74 pg/ml (2.18 -3.98). Antibodies were TPO Ab 1.8, TSI < 89% (<140), Anti Tg Ab 0.9 IU/ml (0.0 - 4.0). THBG was 27 ug/ml (13-39). Alpha subunit was 0.40 ng/dl (<1.02). Genetic test revealed novel mutation in THRB gene, NM_000461.4:c.1362G>T (p.Leu454Phe). It was reported as a novel autosomal dominant missense variant in the THRB gene and was considered as pathogenic. Conclusion: Patients with RTH are usually asymptomatic even with high free T4 and free T3. TSH will be slightly high or normal due to failure to suppress hypothalamic-pituitary- thyroid axis. Most common clinical findings include goiter, hyperactivity and tachycardia.Tachycardia can present as heart predominantly expresses alpha isoform of the thyroid hormone receptor [2]. It may be mistaken with diagnosis of hyperthyroidism. Error in treatment with anti-thyroid agents or radioactive iodine ablation or thyroidectomy can be problematic. Reference 1. Lafranchi SH, Snyder DB, Sesser DE, et al. Follow up of newborns with elevated screening T4 concentrations. J Pediatr 2003; 143:296 2. Weiss RE, Murata Y, Cua K, et al. Thyroid hormone action in liver, heart and energy expenditure in thyroid hormone receptor beta deficient mice. Endocrinology 1998;139:4945

SUN-LB097 Thyroid Hormone Resistance Simulating Graves Disease

Background: Thyroid hormone actions are mediated by nuclear receptors, thyroid receptor TRα and TRβ encoded by THRA and THRB. Resistance to thyroid hormone (RTH) is characterized by elevated thyroid hormone (TH) along with non-suppressed thyroid-stimulating hormone (TSH). Approximately 85 percent of cases are due to a defect in the THRβ gene (RTH-β). The clinical spectrum ranges from isolated biochemical abnormalities to hyperthyroidism or hypothyroidism. Case description: An adolescent female was initially evaluated by an outside endocrinologist at age 15 for hand tremors, tachycardia, and hypertension. She was diagnosed with hyperthyroidism and treated with methimazole in escalating doses without complete symptom remission. In reviewing her records, thyroid function tests had been abnormal since age 3.5 years with high total T4 (TT4) 20.3 ng/dl, high total T3 (TT3) 294 ng/dl, and normal TSH 3.6 µIU/mL. Iodine-123 uptake was 41% at 24 hours, slightly elevated. No treatment had been prescribed before age 15. Family history revealed that father & multiple paternal relatives had high levels of thyroid hormones but no apparent symptoms of hyperthyroidism. Mother, MGM and maternal aunt had hypothyroidism. The proband’s physical exam was notable for normal pulse and blood pressure and a prominent goiter. Thyroid function tests while taking up to 25 mg methimazole daily showed markedly elevated TT4 20.3 ng/dl, TT3 254 ng/dl, progressively rising TSH (3.6 up to 10 µIU/ml), normal TBG 22 µg/ml and negative titers to TSH receptors, TSI, and anti-thyroid peroxidase antibodies. Due to intermittent tachycardia to 200 bpm, atenolol was increased from 25 to 50 mg/day. Cardiac evaluation showed no intrinsic abnormalities. The gradual tapering of methimazole resulted in increasing TT4 and TT3 with normalization of TSH. Repeat I-123 uptake obtained 1 month after discontinuing methimazole was markedly elevated at 24h (75%). Estimated thyroid weight was 40 grams. Genotyping was heterozygous for the c.1313G>A (p.Arg438His), a known pathogenic variant in the THRβ gene. Conclusion: Resistance to thyroid hormone should be suspected in the setting of variable symptoms of hyperthyroidism, abnormally high serum levels of thyroid hormone with non-suppressed TSH, and negative Graves’ disease antibodies. Elevated I-123 uptake may be found in RTH, but also may have been caused by prior methimazole treatment. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. s presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.

SUN-546 Coexistent Resistance to Thyroid Hormone Beta and Viral Thyroiditis

Background Resistance to thyroid hormone beta (RTHbeta) is a rare genetic disorder caused by a defective beta form of the thyroid hormone receptor and is characterized by elevated T3 and T4, non-suppressed TSH and variable tissue resistance to thyroid hormone (TH). In most cases a heterozygous mutation in THRB gene is identified. Clinical case A 32 year old adopted Caucasian woman presented with chest pain in the primary care setting in December 2016. Associated symptoms included palpitations, insomnia, poor concentration, restlessness, tremor, mood swings, headaches, irritability, increased appetite, dry scalp, cold extremities, weight gain and diarrhoea. She had no goitre. Based on thyroid function test (TFT) results, she was suspected to have hyperthyroidism and was commenced on antithyroid drugs for 13 months, but treatment was later stopped due to mouth ulcers. At this stage, further tests in our hospital showed elevated fT3 (8.4 pmol/L, RR 3.5-6.5 pmol/L) and fT4 (33.5 pmol/L, RR 10.0-19.8 pmol/L) and non-suppressed TSH (1.35 mU/L, RR 0.35-5.50 mU/L), without evidence of assay interference. SHBG and MRI pituitary were normal. THRB sequencing identified a heterozygous pathogenic mutation (R438H). She further reported that she struggled in school which prevented her from completing university education and remembered that her biological mother had learning disability. She was further assessed in our clinical research facility. Surprisingly, TFT results were very different: fT3 23.6 pmol/L, fT4 97.3 pmol/L and fully suppressed TSH (<0.03mU/L). Resting energy expenditure (REE) measured by indirect calorimetry was markedly raised [0.214 MJ/kg of lean body mass (LBM)]; compared to that seen in healthy controls (mean (SD): 0.148 (0.013) MJ/kg LBM). Given a recent coryzal illness and negative TRAB, thyrotoxicosis was deemed to be in keeping with thyroiditis. The TFT pattern evolved, without treatment, to mild hypothyroidism (fT3 6.8 pmol/L, fT4 16.2 pmol/L and TSH 21.54 mU/L), then returned to the pattern at presentation: elevated fT3 and fT4 and non-suppressed TSH (fT3 10.6 pmol/L, fT4 31.6 pmol/L, TSH 2.09 mU/L). Given ongoing thyrotoxic symptoms, identical to those present at time of referral, Tri-iodothyroacetic Acid (TRIAC) was commenced. Conclusion Coincident thyroid dysfunction can further complicate interpretation of TFTs in patients with RTHbeta. Notably, individuals with RTHbeta and coexistent thyrotoxicosis can exhibit a suppressed TSH, with underlying pituitary resistance to TH action only becoming evident once TH levels fall. Although thyroiditis rarely complicates RTHbeta, it has been reported that autoimmune thyroid disease occurs more commonly, so interpretation of such unusual TFT patterns may be required during the course of management of these individuals.

SAT-LB094 The Role of Thyroid Hormone in the Beneficial Effects of Stretching

Pain after musculoskeletal injury is a widespread problem significantly affecting quality of life. Stretching is a common therapy that targets connective tissue that can reduce inflammation and collagen production which otherwise could interfere with normal tissue repair [1]. Thyroid hormone (TH) is critical for a diverse range of biological functions, and TH action is controlled at many levels including production, secretion, transport into the cell, TH receptor and cofactor expression, and by tissue- and cell-specific local deiodination that can either activate or inactivate TH. Studies have found T3-treatment significantly attenuated experimental lung injury and further, T3-treatment has been shown to antagonize well known mediators of fibrosis including TGFB-1, leading to less collagen deposition in liver and skin fibrosis [2, 3]. We hypothesized that stretching will increase T3-action in fibroblasts residing in subcutaneous connective tissue, resulting in less fibrosis. Using an in vivo model, C57BL/6J mice were stretched once for 10 minutes by gently lifting at the base of the tail until reaching a 45° angle while allowing the front paws a grasp a horizontal bar. Control animals were either housed individually for 10 minutes to mimic the stressful effects of handling (non-stretched + stress) or remained in their home cage (non-stretched - stress). Lower back subcutaneous connective tissue was collected 24h later to assess gene expression. We found that TH receptor alpha and beta (Thra and Thrb) were both expressed, as well as the TH transporters MCT8, MCT10, Lat1, and Lat2, while expression of thyroid hormone activating and inactivating deiodinases (Dio2 and Dio3 respectively) was negligible. Notably, comparison to the naïve, non-stretched - stress group indicated that the stress of handling alone appeared to change the expression of many genes including Thra and Thrb. Interestingly, comparisons between stretched and non-stretched + stress groups revealed decreased expression of genes involved in collagen synthesis including Col1a1 and CTGF. In conclusion, connective tissue has the necessary components to respond to T3 and one acute session of stretching was sufficient to decrease expression of genes associated with fibrosis although components of the TH action-pathway were not specifically changed.

SAT-571 Restoration of Thyroid Hormone Receptor Beta Signaling Reprograms Anaplastic Thyroid Cancer Cells

Anaplastic thyroid cancer (ATC) is among the most lethal human cancers, with an average survival time of six months. These tumors are characterized by rapid local extension, resistance to radioactive iodine therapy and mainstream chemotherapy, and distant metastasis. There are very limited treatment options for this aggressive form of thyroid cancer, highlighting a need for a deeper understanding of its mechanisms for development of new targeted therapies. Loss of expression of the thyroid hormone receptor beta (TRβ) is correlated with aggressive disease and decreased survival in other human cancer types, including breast cancer, hepatocellular carcinoma, and melanoma, suggesting a tumor suppressor role1-3. Decreased TRβ expression is observed in patients with ATC via tissue microarray4 and in representative ATC cell lines5. To test the hypothesis that rescue of TRβ can restore a tumor suppressor program and a more differentiated phenotype in ATC cells, we re-introduced constitutive TRβ expression in the SW1736 ATC cell line by stable lentiviral transduction. Proliferation assays reveal that SW1736 cells expressing TRβ have a 30% decrease in proliferation rate compared to empty vector control cells. This prompted us to examine the differences in the transcriptome between our SW1736 cells expressing TRβ and the empty vector control cells to determine the potential mechanisms underlying this observation. Establishment of TRβ expression restored a transcriptional response to thyroid hormone treatment, in concordance with our proliferation studies. Upon transcript quantitation and downstream pathway analysis, we observed changes in several pathways that are well known to influence thyroid cancer growth, including mTOR, PTEN, and TGFβ signalling. Upstream regulators of this transcriptional response included many epigenetic regulators, most notably BRG1, KDM5B, and BRD4. This suggests that restoration of TRβ signalling results in a ligand-dependent chromatin remodeling response to facilitate the gene expression changes we observed. In addition, we measured changes in markers of thyroid differentiation by qPCR and found that TRβ expression and treatment with thyroid hormone increased expression of several key genes including TPO, DIO1, and NIS. In summary, our data support a role for TRβ as a tumor suppressor and mediator of thyroid differentiation in thyroid cells. Importantly, our analyses will direct further investigation into targets and pathways that can be exploited as therapeutic strategies in ATC. 1. Martinez-Iglesias, O. et al.Cancer Res69, 501-509, (2009). 2. Aranda, A. et al. Trends in endocrinology and metabolism: TEM20, 318-324, (2009). 3. Suzuki, H., et al. Thyroid12, 963-969, (2002). 4. Landa, I. et al.J Clin Invest126, 1052-1066, (2016). 5. Carr, F. E. et al.Endocrinology157, 3278-3292, (2016).

The protective variant rs7173049 at LOXL1 locus impacts on retinoic acid signaling pathway in pseudoexfoliation syndrome.

LOXL1 (lysyl oxidase-like 1) has been identified as the major effect locus in pseudoexfoliation (PEX) syndrome, a fibrotic disorder of the extracellular matrix and frequent cause of chronic open-angle glaucoma. However, all known PEX-associated common variants show allele effect reversal in populations of different ancestry, casting doubt on their biological significance. Based on extensive LOXL1 deep sequencing, we report here the identification of a common non-coding sequence variant, rs7173049A>G, located downstream of LOXL1, consistently associated with a decrease in PEX risk (odds ratio, OR = 0.63; P = 6.33 × 10−31) in nine different ethnic populations. We provide experimental evidence for a functional enhancer-like regulatory activity of the genomic region surrounding rs7173049 influencing expression levels of ISLR2 (immunoglobulin superfamily containing leucine-rich repeat protein 2) and STRA6 [stimulated by retinoic acid (RA) receptor 6], apparently mediated by allele-specific binding of the transcription factor thyroid hormone receptor beta. We further show that the protective rs7173049-G allele correlates with increased tissue expression levels of ISLR2 and STRA6 and that both genes are significantly downregulated in tissues of PEX patients together with other key components of the STRA6 receptor-driven RA signaling pathway. siRNA-mediated downregulation of RA signaling induces upregulation of LOXL1 and PEX-associated matrix genes in PEX-relevant cell types. These data indicate that dysregulation of STRA6 and impaired retinoid metabolism are involved in the pathophysiology of PEX syndrome and that the variant rs7173049-G, which represents the first common variant at the broad LOXL1 locus without allele effect reversal, mediates a protective effect through upregulation of STRA6 in ocular tissues.

SAT-615 A Novel Mutation and Presentation of Thyroid Hormone Resistance in a Neonate

Background: Thyroid hormone resistance (THR) is a rare disorder that usually presents in later childhood to adulthood with elevations in total and free T4 and T3 and inappropriately normal to elevated thyroid stimulating hormone. Patients can have generalized or pituitary resistance to thyroid hormone and can present with ADHD, growth failure and even symptoms of hyperthyroidism. We present a premature neonate with a spontaneous novel mutation of the thyroid hormone receptor beta gene and her course to 3 years of life. Clinical Case: A 35-week female was transferred to the NICU for temperature instability, apnea and feeding difficulties. Newborn screen showed a thyroxine (T4) level of >34.1 ng/dL with concern for hyperthyroidism. Repeat testing showed a thyroid stimulating hormone (TSH) of 3.9 uUI/mL with T4 of 44.8 ng/dL and T3 of 330 ng/dL on day of life 8. Thyroid antibodies were negative. She had a normal brain MRI and thyroid ultrasound. At one week, she developed thrombocytopenia requiring transfusion. She had intermittent sinus tachycardia with mild pulmonary stenosis and a PFO on echocardiogram that was thought to be physiologic. At one month of life, testing revealed a novel spontaneous heterozygous mutation at c.1295delG of THRB gene. In the first year, she developed a milk protein intolerance and failure to thrive. She had gross motor delays and started therapy at 9 months requiring physical, occupational and feeding therapies. Halter monitoring showed intermittent sinus tachycardia that resolved after 6 months of life. She also had mild sleep difficulties early on. There were no other signs of clinical hyperthyroidism. Formal hearing and ophthalmologic testing was normal. Her platelets normalized after 1 month of life and testing for neonatal alloimmune thrombocytopenia was negative. She had oral feeding aversion without swallowing dysfunction and required a gastrostomy tube at age two. She developed obstructive sleep apnea requiring tonsillectomy and adenoidectomy at 2.5 years. Her height and weight remained below the 3rd percentile for the first 2 years of life. After her gastrostomy tube placement, she improved to the 10th percentile for height and weight which is at the bottom end of her genetic potential. She was discharged from PT at age 3. Thyroid function tests showed a marginally elevated TSH at 2 months with otherwise inappropriately normal TSH levels and elevated T4 and T3 levels. Recent thyroid testing at age 3 was TSH 4.04 uIU/mL (0.7-5.97), T3 465ng/dL (83-252) and freeT4 >7.77ng/dL (0.85-1.75). She has not been treated with any thyroid medication. Conclusion: Little is known about THR in the neonatal and early childhood period. This child had neonatal diagnosis with mild signs of hyperthyroidism, thrombocytopenia, feeding dysfunction and FTT early in life with a novel mutation of the THRB gene.