Generation of THRB-GS(E125G_G126S) and THRB-KO human iPSC lines to study noncanonical thyroid hormone signalling

THRB is a nuclear receptor, regulating gene expression dependent on thyroid hormone (TH) binding. The same receptor mediates signaling pathway activation in the cytosol. The challenge is to distinguish which of the two mechanisms is responsible for physiological effects of TH. We established an iPSC cell line with two mutations (E125G_G126S) in the THRB DNA-binding domain, which abrogates nuclear action and, thus, allows to study signaling pathway activation exclusively. We also generated a THRB knockout cell line to abolish all THRB effects. Comparison of WT and these two cell lines allows attribution of thyroid hormone effects to the underlying mechanism.

Thyroid hormone receptor alpha modulates fibrogenesis in hepatic stellate cells

OBJECTIVE

Progressive hepatic fibrosis can be considered the final stage of chronic liver disease. Hepatic stellate cells (HSC) play a central role in liver fibrogenesis. Thyroid hormones (TH, e.g. thyroxine; T4 and triiodothyronine; T3) significantly affect development, growth, cell differentiation and metabolism through activation of TH receptor α and/or β (TRα/β). Here, we evaluated the influence of TH in hepatic fibrogenesis.

DESIGN

Human liver tissue was obtained from explanted livers following transplantation. TRα-deficient (TRα-KO) and wild-type (WT) mice were fed a control or a profibrogenic methionine-choline deficient (MCD) diet. Liver tissue was assessed by qRT-PCR for fibrogenic gene expression. In vitro, HSC were treated with TGFβ in the presence or absence of T3. HSC with stable TRα knockdown and TRα deficient mouse embryonic fibroblasts (MEF) were used to determine receptor-specific function. Activation of HSC and MEF was assessed using the wound healing assay, Western blotting, and qRT-PCR.

RESULTS

TRα and TRβ expression is downregulated in the liver during hepatic fibrogenesis in humans and mice. TRα represents the dominant isoform in HSC. In vitro, T3 blunted TGFβ-induced expression of fibrogenic genes in HSC and abrogated wound healing by modulating TGFβ signalling, which depended on TRα presence. In vivo, TRα-KO enhanced MCD diet-induced liver fibrogenesis.

CONCLUSION

These observations indicate that TH action in non-parenchymal cells is highly relevant. The interaction of TRα with TH regulates the phenotype of HSC via the TGFβ signalling pathway. Thus, the TH-TR axis may be a valuable target for future therapy of liver fibrosis.

Thyroid hormones regulate Zfp423 expression in regionally distinct adipose depots through direct and cell-autonomous action

The hypothalamic pituitary thyroid axis is a major regulator of many differentiation processes, including adipose tissue. However, it remains unclear whether and how thyroid hormone (TH) signaling contributes to preadipocyte commitment and differentiation into mature adipocytes. Here, we show a cell-autonomous effect of TH on the transcriptional regulation of zinc finger protein 423 (Zfp423), an early adipogenic determination factor, in murine adipose depots. Mechanistically, binding of the unliganded TH receptor to a negative TH responsive element within the Zfp423 promoter activates transcriptional activity that is reversed upon TH binding. Zfp423 upregulation is associated with increased GFP+ preadipocyte recruitment in stromal vascular fraction isolated from white fat of hypothyroid Zfp423GFP reporter mice. RNA sequencing identified Zfp423-driven gene programs that are modulated in response to TH during adipogenic differentiation. Collectively, we identified Zfp423 as a key molecule that integrates TH signaling into the regulation of adipose tissue plasticity.

Evolution of non-thyroidal illness syndrome in acute decompensation of liver cirrhosis and acute-on-chronic liver failure

BACKGROUND AND AIMS

Non-thyroidal illness syndrome (NTIS) is frequent in critically ill patients and associated with adverse outcomes. We aimed to characterize the evolution of NTIS in patients with acute decompensation (AD) of cirrhosis and acute-on-chronic liver failure (ACLF), since NTIS is not well described in these newly defined syndromes.

METHODS

Thyroid hormones (TH) were quantified at baseline in consecutive patients with cirrhosis. In addition, 76 inflammatory mediators were quantified by proximity extension analysis assay in a subgroup of patients. Associations between TH, cirrhosis stage, mortality and inflammation were assessed.

RESULTS

Overall, 437 patients were included, of whom 165 (37.8%), 211 (48.3%), and 61 (14%) had compensated cirrhosis (CC), AD, and ACLF. FT₃ concentrations were lower in AD versus CC, and further decreased in ACLF. Importantly, NTIS was present in 83 (39.3%) patients with AD and in 44 (72.1%) patients with ACLF (P<0.001). Yet, TSH and TSH-based indexes (TSH/FT₃-ratio, thyroid index) showed an U-shaped evolution during progression of cirrhosis, suggesting a partially preserved responsiveness of the hypothalamus and pituitary in AD. Infections were associated with lower FT₃ concentrations in AD, but not in ACLF. Low FT₃ concentrations correlated significantly with 90-day mortality. Both, AD/ACLF and NTIS, were associated with signatures of inflammatory mediators, which were partially non-overlapping.

CONCLUSION

NTIS is frequent already in AD and therefore precedes critically illness in a subgroup of patients with decompensated cirrhosis. This might constitute a new paradigm of TH signaling in cirrhosis, offering opportunities to explore preventive effects of TH in AD.

Cardioprotection by Hypothyroidism Is Not Mediated by Favorable Hemodynamics-Role of Canonical Thyroid Hormone Receptor Alpha Signaling

Hypothyroidism has been shown to reduce infarct size in rats, but the underlying mechanisms are unclear. We used isolated pressure-constant perfused hearts of control, hypothyroid and hyperthyroid mice and measured infarct size, functional parameters and phosphorylation of key molecules in cardioprotective signaling with matched heart rate. Compared with controls, hypothyroidism was cardioprotective, while hyperthyroidism was detrimental with enlarged infarct size. Next, we asked how thyroid hormone receptor α (TRα) affects ischemia/reperfusion (IR) injury. Thus, canonical and noncanonical TRα signaling was investigated in the hearts of (i) mice lacking TRα (TRα0), (ii) with a mutation in TRα DNA-binding domain (TRαGS) and (iii) in hyperthyroid TRα0 (TRα0hyper) and TRαGS mice (TRαGShyper). TRα0 mouse hearts were protected against IR injury. Furthermore, infarct size was reduced in the hearts of TRαGS mice that lack canonical TRα signaling but maintain noncanonical TRα action. Hyperthyroidism did not increase infarct size in TRα0 and TRαGS mouse hearts. These cardioprotective effects were not associated with increased phosphorylation of key proteins of RISK, SAFE and eNOS pathways. In summary, chronic hypothyroidism and the lack of canonical TRα signaling are cardioprotective in IR injury and protection is not due to favorable changes in hemodynamics.

The interplay of thyroid hormones and the immune system - where we stand and why we need to know about it

Over the past few years, growing evidence suggests direct crosstalk between thyroid hormones (THs) and the immune system. Components of the immune system were proposed to interfere with the central regulation of systemic TH levels. Conversely, THs regulate innate and adaptive immune responses as immune cells are direct target cells of THs. Accordingly, they express different components of local TH action, such as TH transporters or receptors, but our picture of the interplay between THs and the immune system is still incomplete. This review provides a critical overview of current knowledge regarding the interaction of THs and the immune system with the main focus on local TH action within major innate and adaptive immune cell subsets. Thereby, this review aims to highlight open issues which might help to infer the clinical relevance of THs in host defence in the context of different types of diseases such as infection, ischemic organ injury or cancer.

Noncanonical Thyroid Hormone Receptor α Action Mediates Arterial Vasodilation

CONTEXT

Hypothyroidism impairs cardiovascular health and contributes to endothelial dysfunction with reduced vasodilation. How 3,5,3'-triiodothyronine (T3) and its receptors are involved in the regulation of vasomotion is not yet fully understood. In general, thyroid hormone receptors (TRs) either influence gene expression (canonical action) or rapidly activate intracellular signaling pathways (noncanonical action).

OBJECTIVE

Here we aimed to characterize the T3 action underlying the mechanism of arterial vasodilation and blood pressure (BP) regulation.

METHODS

Mesenteric arteries were isolated from male rats, wild-type (WT) mice, TRα knockout (TRα 0) mice, and from knockin mice with a mutation in the DNA-binding domain (TRα GS). In this mutant, DNA binding and thus canonical action is abrogated while noncanonical signaling is preserved. In a wire myograph system, the isolated vessels were preconstricted with norepinephrine. The response to T3 was measured, and the resulting vasodilation (Δ force [mN]) was normalized to maximum contraction with norepinephrine and expressed as percentage vasodilation after maximal preconstriction with norepinephrine (%NE). Isolated vessels were treated with T3 (1 × 10-15 to 1 × 10-5 mol/L) alone and in combination with the endothelial nitric oxide-synthase (eNOS) inhibitor L-NG-nitroarginine methyl ester (L-NAME) or the phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin. The endothelium was removed to determine the contribution of T3 to endothelium-dependent vasodilation. The physiological relevance of T3-induced vasodilation was determined by in vivo arterial BP measurements in male and female mice.

RESULTS

T3 treatment induced vasodilation of mesenteric arteries from WT mice within 2 minutes (by 21.5 ± 1.7%NE). This effect was absent in arteries from TRα 0 mice (by 5.3 ± 0.6%NE, P < .001 vs WT) but preserved in TRα GS arteries (by 17.2 ± 1.1%NE, not significant vs WT). Inhibition of either eNOS or PI3K reduced T3-mediated vasodilation from 52.7 ± 4.5%NE to 28.5 ± 4.1%NE and 22.7 ± 2.9%NE, respectively. Removal of the endothelium abolished the T3-mediated vasodilation in rat mesenteric arteries (by 36.7 ± 5.4%NE vs 3.5 ± 6.2%NE). In vivo, T3 injection led to a rapid decrease of arterial BP in WT (by 13.9 ± 1.9 mm Hg) and TRα GS mice (by 12.4 ± 1.9 mm Hg), but not in TRα 0 mice (by 4.1 ± 1.9 mm Hg).

CONCLUSION

These results demonstrate that T3 acting through noncanonical TRα action affects cardiovascular physiology by inducing endothelium-dependent vasodilation within minutes via PI3K and eNOS activation.

Evidence-Based Use of Levothyroxine/Liothyronine Combinations in Treating Hypothyroidism: A Consensus Document

BACKGROUND

Fourteen clinical trials have not shown a consistent benefit of combination therapy with levothyroxine (LT4) and liothyronine (LT3). Despite the publication of these trials, combination therapy is widely used and patients reporting benefit continue to generate patient and physician interest in this area. Recent scientific developments may provide insight into this inconsistency and guide future studies.

METHODS

The American Thyroid Association (ATA), British Thyroid Association (BTA), and European Thyroid Association (ETA) held a joint conference on November 3, 2019 (live-streamed between Chicago and London) to review new basic science and clinical evidence regarding combination therapy with presentations and input from 12 content experts. After the presentations, the material was synthesized and used to develop Summary Statements of the current state of knowledge. After review and revision of the material and Summary Statements, there was agreement that there was equipoise for a new clinical trial of combination therapy. Consensus Statements encapsulating the implications of the material discussed with respect to the design of future clinical trials of LT4/LT3 combination therapy were generated. Authors voted upon the Consensus Statements. Iterative changes were made in several rounds of voting and after comments from ATA/BTA/ETA members.

RESULTS

Of 34 Consensus Statements available for voting, 28 received at least 75% agreement, with 13 receiving 100% agreement. Those with 100% agreement included studies being powered to study the effect of deiodinase and thyroid hormone transporter polymorphisms on study outcomes, inclusion of patients dissatisfied with their current therapy and requiring at least 1.2 µg/kg of LT4 daily, use of twice daily LT3 or preferably a slow-release preparation if available, use of patient-reported outcomes as a primary outcome (measured by a tool with both relevant content validity and responsiveness) and patient preference as a secondary outcome, and utilization of a randomized placebo-controlled adequately powered double-blinded parallel design. The remaining statements are presented as potential additional considerations.

DISCUSSION

This article summarizes the areas discussed and presents Consensus Statements to guide development of future clinical trials of LT4/LT3 combination therapy. The results of such redesigned trials are expected to be of benefit to patients and of value to inform future thyroid hormone replacement clinical practice guidelines treatment recommendations.

Evidence-Based Use of Levothyroxine/Liothyronine Combinations in Treating Hypothyroidism: A Consensus Document

Background: Fourteen clinical trials have not shown a consistent benefit of combination therapy with levothyroxine (LT4) and liothyronine (LT3). Despite the publication of these trials, combination therapy is widely used and patients reporting benefit continue to generate patient and physician interest in this area. Recent scientific developments may provide insight into this inconsistency and guide future studies. Methods: The American Thyroid Association (ATA), British Thyroid Association (BTA), and European Thyroid Association (ETA) held a joint conference on November 3, 2019 (live-streamed between Chicago and London) to review new basic science and clinical evidence regarding combination therapy with presentations and input from 12 content experts. After the presentations, the material was synthesized and used to develop Summary Statements of the current state of knowledge. After review and revision of the material and Summary Statements, there was agreement that there was equipoise for a new clinical trial of combination therapy. Consensus Statements encapsulating the implications of the material discussed with respect to the design of future clinical trials of LT4/LT3 combination therapy were generated. Authors voted upon the Consensus Statements. Iterative changes were made in several rounds of voting and after comments from ATA/BTA/ETA members. Results: Of 34 Consensus Statements available for voting, 28 received at least 75% agreement, with 13 receiving 100% agreement. Those with 100% agreement included studies being powered to study the effect of deiodinase and thyroid hormone transporter polymorphisms on study outcomes, inclusion of patients dissatisfied with their current therapy and requiring at least 1.2 μg/kg of LT4 daily, use of twice daily LT3 or preferably a slow-release preparation if available, use of patient-reported outcomes as a primary outcome (measured by a tool with both relevant content validity and responsiveness) and patient preference as a secondary outcome, and utilization of a randomized placebo-controlled adequately powered double-blinded parallel design. The remaining statements are presented as potential additional considerations. Discussion: This article summarizes the areas discussed and presents Consensus Statements to guide development of future clinical trials of LT4/LT3 combination therapy. The results of such redesigned trials are expected to be of benefit to patients and of value to inform future thyroid hormone replacement clinical practice guidelines treatment recommendations.

A Novel Double RET E768D/L790F Mutation Associated with a MEN2B-Like Phenotype

Background: Multiple endocrine neoplasia type 2 (MEN2) is an autosomal dominant disorder caused by mutations in the RET proto-oncogene. MEN2 is classified into two subtypes, MEN 2A and 2B. MEN2B is characterized by early-onset and aggressive medullary thyroid carcinoma (MTC), pheochromocytoma, and characteristic physical features. Patient Findings: We present a 39-year-old male with early-onset metastatic MTC diagnosed at the age of 13 years and physical features typical for MEN2B such as marfanoid habitus, mucosal neuromas, and thickened eyelids. The patient has two first-degree relatives (mother and maternal uncle) with MTC and pheochromocytoma. The mother has similar facial features. RET sequencing revealed a novel tandem RET E768D/L790F germline mutation in exon 13. The patient's mother has the same RET variant. For functional in vitro characterization, wild-type RET, RET E768D, RET L790F, the double RET E768D/L790F mutant, and RET M918T were expressed in HEK293 cells. The novel double RET E768D/L790F mutant increased ligand-independent RET phosphorylation, activation of the mitogen-activated protein kinase (MAPK)-pathway, and colony formation similar to the classical MEN2B RET M918T mutation. Summary: In this male patient with a MEN2B-like phenotype, we identified a novel double RET germline mutation, E768D/L790F. Functional characterization of the double mutant shows similar transforming capacity as RET M918T.

Noncanonical Action of Thyroid Hormone Receptors α and β

Thyroid hormone (TH) is essential for the regulation of many physiological processes, especially growth, organ development, energy metabolism and cardiovascular effects. TH acts via the TH receptors (TR) α and β. By binding to thyroid hormone responsive elements (TREs) on the DNA, TRs regulate expression of TH target genes. Thus, TRs are mainly characterized as ligand dependent transcription factors and regulation of gene expression and protein synthesis is considered the canonical mode of TH/TR action. The demonstration that the ligand-bound TRs α and β also mediate activation of the phosphatidylinositol-3-kinase (PI3K) pathway established noncanonical TH/TR action as an additional mode of TH signaling. Recently, TR mutant mouse models allowed to determine the underlying mode of TH/TR action, either canonical or noncanonical TH/TR signaling, for several physiological TH effects in vivo: Regulation of the hypothalamic-pituitary-thyroid axis requires DNA-binding of TRβ, whereas hepatic triglyceride content appears to be regulated by noncanonical TRβ signaling. TRα mediated effects in bone development are dependent on DNA-binding, whereas several cardiovascular TRα effects are rapid and independent from DNA-binding. Therefore, noncanonical TH/TR action contributes to the overall effects of TH in physiology.

Increased Anaplastic Lymphoma Kinase Activity Induces a Poorly Differentiated Thyroid Carcinoma in Mice

Background: Radioiodine refractory dedifferentiated thyroid cancer is a major clinical challenge. Anaplastic lymphoma kinase (ALK) mutations with increased ALK activity, especially fusion genes, have been suggested to promote thyroid carcinogenesis, leading to development of poorly differentiated thyroid carcinoma (PDTC) and anaplastic thyroid carcinoma. To determine the oncogenic potential of increased ALK activity in thyroid carcinogenesis in vivo, we studied mice with thyrocyte-specific expression of a constitutively active ALK mutant. Methods: Mice carrying a Cre-activated allele of a constitutively active ALK mutant (F1174L) were crossed with mice expressing tamoxifen-inducible Cre recombinase (CreER^T2) under the control of the thyroglobulin (Tg) gene promoter to achieve thyrocyte-specific expression of the ALK mutant (ALK^F1174L mice). Survival, thyroid hormone serum concentration, and tumor development were recorded. Thyroids and lungs were studied histologically. To maintain euthyroidism despite dedifferentiation of the thyroid, a cohort was substituted with levothyroxine (LT4) through drinking water. Results: ALK^F1174L mice developed massively enlarged thyroids, which showed an early loss of normal follicular architecture 12 weeks after tamoxifen injection. A significant decrease in Tg and Nkx-2.1 expression as well as impaired thyroid hormone synthesis confirmed dedifferentiation. Histologically, the mice developed a carcinoma resembling human PDTC with a predominantly trabecular/solid growth pattern and an increased mitotic rate. The tumors showed extrathyroidal extension into the surrounding strap muscles and developed lung metastases. Median survival of ALK^F1174L mice was significantly reduced to five months after tamoxifen injection. Reduced Tg expression and loss of follicular structure led to hypothyroidism with elevated thyrotropin (TSH). To test whether TSH stimulation played a role in thyroid carcinogenesis, we kept ALK^F1174L mice euthyroid by LT4 substitution. These mice developed PDTC with identical histological features compared with hypothyroid mice, demonstrating that PDTC development was due to increased ALK activity and not dependent on TSH stimulation. Conclusion: Expression of a constitutively activated ALK mutant in thyroids of mice leads to development of metastasizing thyroid cancer resembling human PDTC. These results demonstrate in vivo that increased ALK activity is a driver mechanism in thyroid carcinogenesis.

Thyroxine promotes lung cancer growth in an orthotopic mouse model

Thyroid hormones are important for physiology and homeostasis. In addition to nuclear thyroid hormone receptors, the plasma membrane protein integrin αvβ3 has been recognized as a receptor for both thyroxine (T4) and triiodothyronine (T3). Here, we studied whether thyroid hormone promotes growth of murine lung cancer via αvβ3 in vivo. Murine Lewis lung carcinoma cells (3LL), stably transfected with luciferase, were injected into mouse lungs. Tumor growth in untreated mice was compared to hypothyroid mice and hypothyroid mice treated with T3 or T4 with or without the αvβ3 inhibitor 3,5,3',5'-tetraiodothyroacetic acid (Tetrac). Tumor progression was determined by serial in vivo imaging of bioluminescence emitted from the tumor. Tumor weight was recorded at the end of the experiment. Neoangiogenesis was determined by immunohistochemistry for CD31. Tumor growth was reduced in hypothyroidism and increased by T4 treatment. Strikingly, only T4 but not T3 treatment promoted tumor growth. This T4 effect was abrogated by the αvβ3 inhibitor Tetrac. Tumor weight and neoangiogenesis were also significantly increased only in T4-treated mice. The T4 effect on tumor weight and neoangiogenesis was abolished by Tetrac. In vitro, T4 did not stimulate 3LL cell proliferation or signaling pathway activation. We conclude that T4 promotes lung cancer growth in this orthotopic mouse model. The tumor-promoting effect is mediated via the plasma membrane integrin αvβ3 and increased neoangiogenesis rather than direct stimulation of 3LL cells. These data suggest that such effects of levothyroxine may need to be considered in cancer patients on T4 substitution.

Assessment and Management of Anti-Insulin Autoantibodies in Varying Presentations of Insulin Autoimmune Syndrome

Context

Insulin autoimmune syndrome (IAS), spontaneous hyperinsulinemic hypoglycemia due to insulin-binding autoantibodies, may be difficult to distinguish from tumoral or other forms of hyperinsulinemic hypoglycemia, including surreptitious insulin administration. No standardized treatment regimen exists.

Objectives

To evaluate an analytic approach to IAS and responses to different treatments.

Design and Setting

Observational study in the UK Severe Insulin Resistance Service.

Patients

Six patients with hyperinsulinemic hypoglycemia and detectable circulating anti-insulin antibody (IA).

Main Outcome Measures

Glycemia, plasma insulin, and C-peptide concentrations by immunoassay or mass spectrometry (MS). Immunoreactive insulin was determined in the context of polyethylene glycol (PEG) precipitation and gel filtration chromatography (GFC). IA quantification using ELISA and RIA, and IA were further characterized using radioligand binding studies.

Results

All patients were diagnosed with IAS (five IgG, one IgA) based on a high insulin/C-peptide ratio, low insulin recovery after PEG precipitation, and GFC evidence of antibody-bound insulin. Neither ELISA nor RIA result proved diagnostic for every case. MS provided a more robust quantification of insulin in the context of IA. One patient was managed conservatively, four were treated with diazoxide without sustained benefit, and four were treated with immunosuppression with highly variable responses. IA affinity did not appear to influence presentation or prognosis.

Conclusions

IAS should be considered in patients with hyperinsulinemic hypoglycemia and a high insulin/C-peptide ratio. Low insulin recovery on PEG precipitation supports the presence of insulin-binding antibodies, with GFC providing definitive confirmation. Immunomodulatory therapy should be customized according to individual needs and clinical response.

Graves' orbitopathy occurs sex-independently in an autoimmune hyperthyroid mouse model

Graves’ orbitopathy (GO) is the most common extra thyroidal complication of Graves’ disease (GD) and occurs predominantly in women but more severe in men. The reason for this effect of gender on GO is unknown. Herein we studied the manifestation of GO in both sexes of an induced mouse model in absence of additional risk factors present in patients like advanced age, genetic variabilities or smoking. Male and female mice were immunized with human TSHR A-subunit encoding plasmid. Both sexes comparably developed autoimmune hyperthyroidism characterized by TSHR stimulating autoantibodies, elevated T4 values, hyperplastic thyroids and hearts. Autoimmune mice developed inflammatory eye symptoms and proptosis, although males earlier than females. Serial in vivo¹H/¹⁹F-magnetic resonance imaging revealed elevated inflammatory infiltration, increased fat volume and glycosaminoglycan deposition in orbits of both sexes but most significantly in female mice. Histologically, infiltration of T-cells, extension of brown fat and overall collagen deposition were characteristics of GO in male mice. In contrast, female mice developed predominately macrophage infiltration in muscle and connective tissue, and muscle hypertrophy. Apart from sex-dependent variabilities in pathogenesis, disease classification revealed minor sex-differences in incidence and total outcome. In conclusion, sex does not predispose for autoimmune hyperthyroidism and associated GO.

NGS based identification of mutational hotspots for targeted therapy in anaplastic thyroid carcinoma

CONTEXT

Anaplastic thyroid carcinoma (ATC) represents one of the most aggressive carcinomas with no consistent survival benefit when treated with conventional radiochemotherapy. Approaches targeting "oncogene addiction" of ATC are increasingly explored and first promising results have been reported in single case studies.

OBJECTIVE

To determine the prevalence of mutations in known thyroid oncogenes and signalling pathways amendable to targeted therapy in a large cohort of ATC.

RESULTS

In 118 ATC (57 male/ 61 female) a total of 165 mutations were found. Genes involved in the MAPK/ERK and PI3K pathway (BRAF 11.0%, HRAS 4.2%, KRAS 7.6%, NRAS 7.6%, PI3KCA 11.8%) were altered in 33%. Targetable receptor tyrosine kinases were mutated in 11%. The most frequently altered genes were TERT in 86/118 (73%) and p53 in 65/118 (55%) cases. No mutations were found analysing ALK, KIT, MET and mTOR.

MATERIALS AND METHODS

Next generation sequencing (NGS) was performed in FFPE samples from 118 ATC using MiSeq (Illumina) and CLC Cancer Research Workbench (CLCbio; Qiagen) for mutation analysis in: ALK, BRAF, CDKN2A, EGFR, ERBB2, HRAS, KIT, KRAS, MET, mTOR, NRAS, PDGFRA, PI3KCA, p53, RB1, RET and TSC2. Sanger sequencing was used to detect TERT promotor mutations.

CONCLUSIONS

To our knowledge this is the largest study analysing mutations for targeted therapy of ATC. We found that 33% of ATC harbour mutations in pathways amendable to targeted therapy. Molecular screening in ATC is suggested for targeted therapies since current conventional treatment for ATC proved mainly futile.

Mycophenolate plus methylprednisolone versus methylprednisolone alone in active, moderate-to-severe Graves' orbitopathy (MINGO): a randomised, observer-masked, multicentre trial

BACKGROUND

European guidelines recommend intravenous methylprednisolone as first-line treatment for active and severe Graves' orbitopathy; however, it is common for patients to have no response or have relapse after discontinuation of treatment. We aimed to compare the efficacy and safety of add-on mycophenolate to methylprednisolone in comparison with methylprednisolone alone in patients with moderate-to-severe Graves' orbitopathy.

METHODS

MINGO was an observer-masked, multicentre, block-randomised, centre-stratified trial done in two centres in Germany and two in Italy. Patients with active moderate-to-severe Graves' orbitopathy were randomly assigned to receive intravenous methylprednisolone (500 mg once per week for 6 weeks followed by 250 mg per week for 6 weeks) either alone or with mycophenolate (one 360 mg tablet twice per day for 24 weeks). The prespecified primary endpoints were rate of response (reduction of at least two parameters of a composite ophthalmic index [eyelid swelling, clinical activity score, proptosis, lid width, diplopia, and eye muscle motility] without deterioration in any other parameter) at 12 weeks and rate of relapse (a worsening of symptoms that occurred after a response) at 24 and 36 weeks. Rates of response at week 24 and sustained response at week 36 were added as post-hoc outcomes. Prespecified primary outcomes and post-hoc outcomes were assessed in the modified intention-to-treat population (defined as all patients assigned to treatment who received at least one infusion of methylprednisolone, when outcome data were available), and safety was assessed in all patients who received at least one dose of study drug. This trial is registered with the EU Clinical Trials Register, EUDRACT number 2008-002123-93.

FINDINGS

164 patients were enrolled and randomised between Nov 29, 2009, and July 31, 2015. 81 were randomly assigned to receive methylprednisolone alone and 83 to receive methylprednisolone with mycophenolate. In the intention-to-treat population at 12 weeks, responses were observed in 36 (49%) of 73 patients in the monotherapy group and 48 (63%) of 76 patients in the combination group, giving an odds ratio (OR) of 1·76 (95% CI 0·92-3·39, p=0·089). At week 24, 38 (53%) of 72 patients remaining in the monotherapy group and 53 (71%) of 75 patients remaining in the combination therapy group had responded to treatment (2·16, 1·09-4·25, p=0·026). At week 24, relapse occurred in four (11%) of 38 patients in the monotherapy group and four (8%) of 53 patients in the combination group (OR 0·71, 0·17-3·03, p=0·72). At week 36, relapse occurred in an additional three (8%) patients in the monotherapy group and two (4%) patients in the combination group (0·65, 0·12-3·44, p=0·61). At week 36, 31 (46%) of 68 patients in the monotherapy group and 49 (67%) of 73 patients in the combination group had a sustained response (OR 2·44, 1·23-4·82, p=0·011). 23 patients had 24 serious adverse events, with 11 events in ten patients in the combination group and 13 events in 13 patients in the monotherapy group. Mild and moderate (grade 1-2) drug-related adverse events occurred in 16 (20%) of 81 patients receiving monotherapy and 21 (25%) of 83 patients receiving combination therapy (p=0·48).

INTERPRETATION

Although no significant difference was seen in the rate of response at 12 weeks or rate of relapse at 24 and 36 weeks, post-hoc analysis suggested that addition of mycophenolate to treatment with methylprednisolone improved rate of response to therapy by 24 weeks in patients with active and moderate-to-severe Graves' orbitopathy.

FUNDING

Novartis, Germany.

Clinical Characterization of the Pheochromocytoma and Paraganglioma Susceptibility Genes SDHA, TMEM127, MAX, and SDHAF2 for Gene-Informed Prevention

Importance

Effective cancer prevention is based on accurate molecular diagnosis and results of genetic family screening, genotype-informed risk assessment, and tailored strategies for early diagnosis. The expanding etiology for hereditary pheochromocytomas and paragangliomas has recently included SDHA, TMEM127, MAX, and SDHAF2 as susceptibility genes. Clinical management guidelines for patients with germline mutations in these 4 newly included genes are lacking.

Objective

To study the clinical spectra and age-related penetrance of individuals with mutations in the SDHA, TMEM127, MAX, and SDHAF2 genes.

Design, Setting, and Patients

This study analyzed the prospective, longitudinally followed up European-American-Asian Pheochromocytoma-Paraganglioma Registry for prevalence of SDHA, TMEM127, MAX, and SDHAF2 germline mutation carriers from 1993 to 2016. Genetic predictive testing and clinical investigation by imaging from neck to pelvis was offered to mutation-positive registrants and their relatives to clinically characterize the pheochromocytoma/paraganglioma diseases associated with mutations of the 4 new genes.

Main Outcomes and Measures

Prevalence and spectra of germline mutations in the SDHA, TMEM127, MAX, and SDHAF2 genes were assessed. The clinical features of SDHA, TMEM127, MAX, and SDHAF2 disease were characterized.

Results

Of 972 unrelated registrants without mutations in the classic pheochromocytoma- and paraganglioma-associated genes (632 female [65.0%] and 340 male [35.0%]; age range, 8-80; mean [SD] age, 41.0 [13.3] years), 58 (6.0%) carried germline mutations of interest, including 29 SDHA, 20 TMEM127, 8 MAX, and 1 SDHAF2. Fifty-three of 58 patients (91%) had familial, multiple, extra-adrenal, and/or malignant tumors and/or were younger than 40 years. Newly uncovered are 7 of 63 (11%) malignant pheochromocytomas and paragangliomas in SDHA and TMEM127 disease. SDHA disease occurred as early as 8 years of age. Extra-adrenal tumors occurred in 28 mutation carriers (48%) and in 23 of 29 SDHA mutation carriers (79%), particularly with head and neck paraganglioma. MAX disease occurred almost exclusively in the adrenal glands with frequently bilateral tumors. Penetrance in the largest subset, SDHA carriers, was 39% at 40 years of age and is statistically different in index patients (45%) vs mutation-carrying relatives (13%; P < .001).

Conclusions and Relevance

The SDHA, TMEM127, MAX, and SDHAF2 genes may contribute to hereditary pheochromocytoma and paraganglioma. Genetic testing is recommended in patients at clinically high risk if the classic genes are mutation negative. Gene-specific prevention and/or early detection requires regular, systematic whole-body investigation.

Fetal Exposure to High Maternal Thyroid Hormone Levels Causes Central Resistance to Thyroid Hormone in Adult Humans and Mice

Context

Fetuses exposed to the high thyroid hormone (TH) levels of mothers with resistance to thyroid hormone beta (RTH-β), due to mutations in the THRB gene, have low birth weight and suppressed TSH.

Objective

Determine if such exposure to high TH levels in embryonic life has a long-term effect into adulthood.

Design

Observations in humans with a parallel design on animals to obtain a preliminary information regarding mechanism.

Setting

University research centers.

Patients or other participants

Humans and mice with no RTH-β exposed during intrauterine life to high TH levels from mothers who were euthyroid due to RTH-β. Controls were humans and mice of the same genotype but born to fathers with RTH-β and mothers without RTH-β and thus, with normal serum TH levels.

Interventions

TSH responses to stimulation with thyrotropin-releasing hormone (TRH) during adult life in humans and male mice before and after treatment with triiodothyronine (T3). We also measured gene expression in anterior pituitaries, hypothalami, and cerebral cortices of mice.

Results

Adult humans and mice without RTH-β, exposed to high maternal TH in utero, showed persistent central resistance to TH, as evidenced by reduced responses of serum TSH to TRH when treated with T3. In mice, anterior pituitary TSH-β and deiodinase 3 (D3) mRNAs, but not hypothalamic and cerebral cortex D3, were increased.

Conclusions

Adult humans and mice without RTH-β exposed in utero to high maternal TH levels have persistent central resistance to TH. This is likely mediated by the increased expression of D3 in the anterior pituitary, enhancing local T3 degradation.

A Novel Mutation in the TBG Gene Producing Partial Thyroxine-Binding Globulin Deficiency (Glencoe) Identified in 2 Families

BACKGROUND

Thyroxine-binding globulin (TBG) is the major thyroid hormone transport protein in serum. Located on the long arm of the X chromosome, TBG (SERPINA7) gene mutations most commonly produce inherited partial TBG deficiency (TBG-PD).

OBJECTIVE

We report a novel TBG variant associated with TBG-PD identified in 2 different families of Ashkenazi origin residing in greater Chicago.

METHODS

Family 1: The proband was 12.6 years old when she presented for delayed puberty and was placed on L-T₄. Although her serum TSH normalized, her serum T₄ remained low. Affected family members had low total T₄ and T₃, but a normal free T₄ index, even when serum TSH concentrations were normal. Family 2: A 71-year-old male presented with a history of a nonfunctioning pituitary adenoma and normal pituitary axes except for low total T₄ and T₃. His brother had a similar thyroid phenotype.

RESULTS

Following direct DNA sequencing, both index patients were found to carry a missense mutation in the TBG gene (c.751T>G) producing p.V215G. The proposita of family 1 was heterozygous and the proband in family 2 was hemizygous for the mutation. Isoelectric focusing showed no alteration in the TBG isoforms and in vitro expression demonstrated a TBG with reduced affinity for T₄.

CONCLUSIONS

We report a novel mutation in the TBG gene in 2 unrelated families that produces a molecule with reduced affinity for T₄ resulting in low serum T₄. However, the physical properties of the mutant molecule remained unaltered as determined by isoelectric focusing.

Thyroid Hormone Signaling Pathways: Time for a More Precise Nomenclature

Current literature makes a distinction between two pathways for thyroid hormone signaling: genomic and nongenomic. However, this classification is a source of confusion. We propose a clarification in the nomenclature that may help to avoid unproductive controversies and favor progress in this field of research. Four types of thyroid hormone signaling are defined, and the experimental criteria for classification are discussed.

A 6-Base Pair in Frame Germline Deletion in Exon 7 Of RET Leads to Increased RET Phosphorylation, ERK Activation, and MEN2A

CONTEXT

Multiple endocrine neoplasia type 2 (MEN2) is usually caused by missense mutations in the proto-oncogene, RET.

OBJECTIVE

This study aimed to determine the mutation underlying MEN2A in a female patient diagnosed with bilateral pheochromocytoma at age 31 years and with medullary thyroid carcinoma (MTC) 6 years later.

METHODS

Leukocyte DNA was used for exome and Sanger sequencing. Wild-type (WT) RET and mutants were expressed in HEK293 cells. Activation of MAPK/ERK and PI3K/AKT was analyzed by Western blotting and luciferase assay. The effect of RET mutants on cell proliferation was tested in a colony forming assay.

RESULTS

Exome sequencing revealed a 6-nucleotide/2-amino acid in-frame deletion in exon 7 of RET (c.1512_1517delGGAGGG, p.505_506del). In vitro expression showed that phosphorylation of the crucial tyrosine 905 was much stronger in the p.505_506del RET mutant compared with WT RET, indicating ligand-independent autophosphorylation. Furthermore, the p.505_506del RET mutant induced a strong activation of the MAPK/ERK pathway and the PI3K/AKT pathway. Consequently, the p.505_506del RET mutant cells increased HEK293 colony formation 4-fold compared with WT RET.

CONCLUSION

The finding of bilateral pheochromocytoma and MTC in our patient was highly suspicious of a RET mutation. Exome sequencing revealed a 6-base-pair deletion in exon 7 of RET, an exon not yet associated with MEN2. Increased ligand-independent phosphorylation of the p.505_506del RET mutant, increased activation of downstream pathways, and stimulation of cell proliferation demonstrated the pathogenic nature of the mutation. We therefore recommend screening the whole sequence of RET in MTC and pheochromocytoma patients with red flags for a genetic cause.

Differences in Mouse Hepatic Thyroid Hormone Transporter Expression with Age and Hyperthyroidism

BACKGROUND

Clinical features of thyroid dysfunction vary with age, and an oligosymptomatic presentation of hyperthyroidism is frequently observed in the elderly. This suggests age modulation of thyroid hormone (TH) action, which may occur, for example, by alterations in TH production, metabolism and/or TH action in target organs.

OBJECTIVES

In this paper, we address possible changes in TH transporter expression in liver tissues as a mechanism of age-dependent variation in TH action.

METHODS

Chronic hyperthyroidism was induced in 4- and 20-month-old C57BL6/NTac male mice (n = 8-10) by intraperitoneal injections of 1 µg/g body weight L-thyroxine (T4) every 48 h over 7 weeks. Control animals were injected with PBS. Total RNA was isolated from liver samples for analysis of the TH transporter and TH-responsive gene expression. TH concentrations were determined in mice sera.

RESULTS

Baseline serum free T4 (fT4) concentrations were significantly higher in euthyroid young compared to old mice. T4 treatment increased total T4, fT4 and free triiodothyronine to comparable concentrations in young and old mice. In the euthyroid state, TH transporter expression was significantly higher in old than in young mice, except for Mct8 and Oatp1a1 expression levels. Hyperthyroidism resulted in upregulation of Mct10, Lat1 and Lat2 in liver tissue, while Oatp1a1, Oatp1b2 and Oatp1a4 expression was downregulated. This effect was preserved in old animals.

CONCLUSION

Here, we show age-dependent differences in TH transporter mRNA expression in the euthyroid and hyperthyroid state of mice focusing on the liver as a classical TH target organ.

Sex-Dependent Claudin-1 Expression in the Liver of Euthyroid and Hypothyroid Mice

BACKGROUND

In the liver the tight junction protein claudin-1 plays an important role in bile secretion by maintaining the paracellular barrier of bile canaliculi and the bile duct. A diminished bile excretion has been found in hypothyroid patients, and the prevalence of gallstones is increased in hypothyroidism. This association, however, only applies for men and is in contrast to the well-established female preponderance of biliary disease in the general population.

OBJECTIVES

We hypothesized that hypothyroidism could lead to altered claudin-1 expression in the liver, and that this effect may be sex specific.

METHODS

We characterized claudin-1 expression and localization in livers of euthyroid and hypothyroid male and female C57BL/6NTac mice by real-time PCR, Western blot and immunofluorescence.

RESULTS

Claudin-1 is expressed in canalicular regions and the bile ducts of the murine liver. Livers of female mice showed lower claudin-1 expression than male livers. In hypothyroid livers, female animals showed an elevated claudin-1 expression, whereas reduced claudin-1 expression was found in male animals compared to the euthyroid controls.

CONCLUSION

We demonstrate a correlation between claudin-1 expression and hypothyroidism in the murine liver. Furthermore, a sex-dependent alteration of claudin-1 expression was found.

Two Novel Mutations in the Serpina7 Gene Are Associated with Complete Deficiency of Thyroxine-Binding Globulin

BACKGROUND

Thyroxine-binding globulin (TBG) is the main transport protein for T4 in blood. Until now, 22 mutations leading to complete TBG deficiency (TBG-CD) have been reported.

OBJECTIVE

We report two mutations associated with TBG-CD found in patients from Andrews, S.C., USA (TBG-CD-Andrews), and Berlin, Germany (TBG-CD-Berlin).

METHODS

Automated chemiluminescence immunoassays were used for the determination of TSH, free and total T4 and T3 (fT4, TT4, TT3) and TBG. Direct DNA sequencing was used to identify the TBG mutations in the propositi.

RESULTS

TBG-CD-Andrews was found in a 1-month-old boy who was euthyroid with normal TSH and fT4, but reduced TT4, indicating TBG deficiency. TBG was not detectable, confirming TBG-CD. No mutation in the coding region and the promoter of the TBG gene was found, but a single nucleotide substitution in intron 1 disrupts the donor splice site of exon 0 (IVS1+2T>C). Another mutation was found in an 11-year-old boy. He was also euthyroid with normal fT4 and TSH. However, TT4 and TT3 were low, suggesting TBG-CD. Sequencing revealed a 79-nucleotide deletion, ranging from intron 3 into exon 3.

CONCLUSION

We report two novel mutations of the TBG gene associated with TBG-CD. Whereas most TBG-CDs are caused by small deletions, in TBG-CD-Andrews the disruption of a donor splice site was detected, whilst in TBG-CD-Berlin the largest deletion in the Serpina7 gene to date was found.

The Effects of Thyroid Hormones on Gene Expression of Acyl-Coenzyme A Thioesterases in Adipose Tissue and Liver of Mice

BACKGROUND

Thyroid hormones (TH) exert pleiotropic effects on glucose and lipid homeostasis. However, it is as yet unclear how TH regulate lipid storage and utilization in order to adapt to metabolic needs. Acyl-CoA thioesterases (ACOTs) have been proposed to play a regulatory role in the metabolism of fatty acids.

OBJECTIVES

We investigated the interaction between thyroid dysfunction and Acot expression in adipose tissues and livers of thyrotoxic and hypothyroid mice.

METHODS

Ten-week-old female C57BL/6NTac mice (n = 10/group) were made hyperthyroid by the application of L-thyroxine (2 µg/ml in drinking water) for 4 weeks. Hypothyroidism was induced in 10-week-old mice by feeding an iodine-free chow supplemented with 0.15% PTU for 4 weeks. We measured mRNA expression levels of Acot8, 11 and 13 in the liver and epididymal and inguinal white and brown adipose tissues (BAT). Furthermore, we investigated hepatic Acot gene expression in TRα- and TRβ-deficient mice.

RESULTS

We showed that the expression of Acot8, 11 and 13 is predominantly stimulated by a thyrotoxic state in the epididymal white adipose tissue. In contrast, hypothyroidism predominantly induces the expression of Acot8 in BAT in comparison with BAT of thyrotoxic and euthyroid mice (p < 0.01). However, no significant changes in Acot expression were observed in inguinal white adipose tissue. In liver, Acot gene expression is collectively elicited by a thyrotoxic state.

CONCLUSIONS

These data suggest that ACOTs are targets of TH and are likely to influence 3,5,3'-triiodo-L-thyronine-orchestrated mechanisms of lipid uptake, storage and utilization to adapt the regulation of metabolic demands.

Higher Thyroid-Stimulating Hormone, Triiodothyronine and Thyroxine Values Are Associated with Better Outcome in Acute Liver Failure

Introduction

Changes in thyroid hormone levels, mostly as non-thyroidal illness syndrome (NTIS), have been described in many diseases. However, the relationship between acute liver failure (ALF) and thyroid hormone levels has not yet been clarified. The present study evaluates potential correlations of select thyroid functional parameters with ALF.

Methods

84 consecutively recruited ALF patients were grouped according to the outcome of ALF (spontaneous recovery: SR; transplantation or death: NSR). TSH, free thyroxine (fT4), free triiodothyronine (fT3), T4, and T3 were determined.

Results

More than 50% of patients with ALF presented with abnormal thyroid parameters. These patients had greater risk for an adverse outcome than euthyroid patients. SR patients had significantly higher TSH, T4, and T3 concentrations than NSR patients. Albumin concentrations were significantly higher in SR than in NSR. In vitro T3 treatment was not able to rescue primary human hepatocytes from acetaminophen induced changes in mRNA expression.

Conclusions

In patients with ALF, TSH and total thyroid hormone levels differed significantly between SR patients and NSR patients. This might be related to diminished liver-derived transport proteins, such as albumin, in more severe forms of ALF. Thyroid parameters may serve as additional indicators of ALF severity.

Successful treatment of type B insulin resistance with rituximab

CONTEXT

Type B insulin resistance is a very rare disease caused by autoantibodies against the insulin receptor. The mortality of type B insulin resistance is high (>50%), and management of this disease is not yet standardized. We report the successful treatment of a patient with type B insulin resistance with rituximab, cyclophosphamide, and prednisone.

CASE DESCRIPTION

A 45-year-old woman presented with unintended weight loss of 20 kg, unusually widespread acanthosis nigricans, and glucose levels > 500 mg/dL, which could not be controlled with up to 600 IU/d of insulin. Because of the severity of the insulin resistance combined with features of insulin deficiency, type B insulin resistance was suspected. Detection of high levels of insulin receptor autoantibodies confirmed the diagnosis. Neither immunosuppressive therapy with Ig iv nor plasmapheresis had an effect on glucose levels or insulin dose. Because the patient's condition was deteriorating, we started rituximab (750 mg/m(2) in two doses 2 wk apart) together with cyclophosphamide (100 mg/d orally) and dexamethasone 40 mg/d for 4 days. Two months after initiation of rituximab therapy, fasting glucose levels ranged from 80 to 110 mg/dL and could be controlled with very low insulin doses. Glycated hemoglobin decreased from 11.8 to 6.5%. Two months later, insulin therapy was stopped, and the patient showed normal blood glucose readings.

CONCLUSION

In this patient with type B insulin resistance, Ig treatment and plasmapheresis failed to improve the condition. Finally, treatment with rituximab, cyclophosphamide, and steroids was successful in inducing a complete remission.

Modulation of monocarboxylate transporter 8 oligomerization by specific pathogenic mutations

The monocarboxylate transporter 8 (MCT8) is a member of the major facilitator superfamily (MFS). These membrane-spanning proteins facilitate translocation of a variety of substrates, MCT8 specifically transports iodothyronines. Mutations in MCT8 are the underlying cause of severe X-linked psychomotor retardation. At the molecular level, such mutations led to deficiencies in substrate translocation due to reduced cell-surface expression, impaired substrate binding, or decreased substrate translocation capabilities. However, the causal relationships between genotypes, molecular features of mutated MCT8, and patient characteristics have not yet been comprehensively deciphered. We investigated the relationship between pathogenic mutants of MCT8 and their capacity to form dimers (presumably oligomeric structures) as a potential regulatory parameter of the transport function of MCT8. Fourteen pathogenic variants of MCT8 were investigated in vitro with respect to their capacity to form oligomers. Particular mutations close to the substrate translocation channel (S194F, A224T, L434W, and R445C) were found to inhibit dimerization of MCT8. This finding is in contrast to those for other transporters or transmembrane proteins, in which substitutions predominantly at the outer-surface inhibit oligomerization. Moreover, specific mutations of MCT8 located in transmembrane helix 2 (del230F, V235M, and ins236V) increased the capacity of MCT8 variants to dimerize. We analyzed the localization of MCT8 dimers in a cellular context, demonstrating differences in MCT8 dimer formation and distribution. In summary, our results add a new link between the functions (substrate transport) and protein organization (dimerization) of MCT8, and might be of relevance for other members of the MFS. Finally, the findings are discussed in relationship to functional data combined with structural-mechanistical insights into MCT8.

A novel mechanism of inherited TBG deficiency: mutation in a liver-specific enhancer

CONTEXT

T4-binding globulin (TBG), a protein secreted by the liver, is the main thyroid hormone (TH) transporter in human serum. TBG deficiency is characterized by reduced serum TH levels, but normal free TH and TSH and absent clinical manifestations. The inherited form of TBG deficiency is usually due to a mutation in the TBG gene located on the X-chromosome.

OBJECTIVE

Among the 75 families with X-chromosome-linked TBG deficiency identified in our laboratory, no mutations in the TBG gene were found in four families. The aim of the study was to identify the mechanism of TBG deficiency in these four families using biochemical and genetic studies.

DESIGN

Observational cohort, prospective.

SETTING

University research center.

PATIENTS

Four families with inherited TBG deficiency and no mutations in the TBG gene.

INTERVENTION

Clinical evaluation, thyroid function tests, and targeted resequencing of 1 Mb of the X-chromosome.

RESULTS

Next-generation sequencing identified a novel G to A variant 20 kb downstream of the TBG gene in all four families. In silico analysis predicted that the variant resides within a liver-specific enhancer. In vitro studies confirmed the enhancer activity of a 2.2-kb fragment of genomic DNA containing the novel variant and showed that the mutation reduces the activity of this enhancer. The affected subjects share a haplotype of 8 Mb surrounding the mutation, and the most recent common ancestor among the four families was estimated to be 19.5 generations ago (95% confidence intervals, 10.4-37).

CONCLUSIONS

To our knowledge, the present study is the first report of an inherited endocrine disorder caused by a mutation in an enhancer region.

Diabetes insipidus as a rare cause of acute cognitive impairment in multiple sclerosis

Multiple sclerosis (MS) is a complex neurodegenerative disease presenting with a diversity of clinical symptoms including palsy and cognitive impairment. We present a 59-year-old woman with a history of secondary progressive MS since 1987, who was referred to our department because of recent onset of confusion and polydipsia. Initial lab tests showed mildly elevated serum sodium levels and low urine osmolality. Under water deprivation, diuresis and low urine osmolality persisted and serum sodium levels rose above 150 mmol/l. Oral desmopressin resulted in normalisation of serum sodium as well as urine osmolarity, confirming a diagnosis of central diabetes insipidus. As drug-induced diabetes could be excluded, pituitary magnetic resonance imaging (MRI) was performed. A demyelinating lesion was detected in the hypothalamus. The patient was started on oral desmopressin treatment (0.2 mg/day). Fluid intake and serum sodium levels have since remained normal. In summary, we report the rare case of a patient presenting with diabetes insipidus due to progressive MS. Diabetes insipidus should be considered in MS patients who develop new onset of polydipsia.

Long-term prognosis of patients with pediatric pheochromocytoma

A third of patients with paraganglial tumors, pheochromocytoma, and paraganglioma, carry germline mutations in one of the susceptibility genes, RET, VHL, NF1, SDHAF2, SDHA, SDHB, SDHC, SDHD, TMEM127, and MAX. Despite increasing importance, data for long-term prognosis are scarce in pediatric presentations. The European-American-Pheochromocytoma-Paraganglioma-Registry, with a total of 2001 patients with confirmed paraganglial tumors, was the platform for this study. Molecular genetic and phenotypic classification and assessment of gene-specific long-term outcome with second and/or malignant paraganglial tumors and life expectancy were performed in patients diagnosed at <18 years. Of 177 eligible registrants, 80% had mutations, 49% VHL, 15% SDHB, 10% SDHD, 4% NF1, and one patient each in RET, SDHA, and SDHC. A second primary paraganglial tumor developed in 38% with increasing frequency over time, reaching 50% at 30 years after initial diagnosis. Their prevalence was associated with hereditary disease (P=0.001), particularly in VHL and SDHD mutation carriers (VHL vs others, P=0.001 and SDHD vs others, P=0.042). A total of 16 (9%) patients with hereditary disease had malignant tumors, ten at initial diagnosis and another six during follow-up. The highest prevalence was associated with SDHB (SDHB vs others, P<0.001). Eight patients died (5%), all of whom had germline mutations. Mean life expectancy was 62 years with hereditary disease. Hereditary disease and the underlying germline mutation define the long-term prognosis of pediatric patients in terms of prevalence and time of second primaries, malignant transformation, and survival. Based on these data, gene-adjusted, specific surveillance guidelines can help effective preventive medicine.

Thyroid hormone, thyroid hormone receptors, and cancer: a clinical perspective

Thyroid hormones (THs) may play a role in diseases other than hyper- and hypothyroidism. Several lines of evidence suggest tumor-promoting effects of TH and TH receptors. They are possibly mediated by phosphatidylinositol-3-kinase and MAPK and involve among others stimulation of angiogenesis via αvβ3. Thus, an increased risk for colon, lung, prostate, and breast cancer with lower TSH has been demonstrated in epidemiological studies, even suggesting a TH dose effect on cancer occurrence. Furthermore, higher TH levels were associated with an advanced clinical stage of breast and prostate cancer. In rodent models, TH stimulated growth and metastasis of tumor transplants, whereas hypothyroidism had opposite effects. In clinical studies of glioblastoma and head and neck cancer, hypothyroid patients showed longer survival than euthyroid patients. Also, patients with renal cell cancer that were treated with the tyrosine kinase inhibitor sunitinib and developed hypothyroidism in due course showed significantly longer survival than patients that remained euthyroid. Development of hypothyroidism was an independent predictor for survival in two studies. Yet, it is still possible that hypothyroidism is only a surrogate marker for treatment efficacy and does not positively influence treatment outcome by itself. Future cancer treatment studies, especially with substances that can induce hypothyroidism, should therefore be designed in a way that allows for an analysis of thyroid function status and its contribution on treatment outcome.

Treatment of advanced medullary thyroid carcinoma with a combination of cyclophosphamide, vincristine, and dacarbazine: a single-center experience

OBJECTIVE

Experience with chemotherapy in patients with medullary thyroid carcinomas (MTC) is limited. This retrospective study evaluated the outcome of a combination of cyclophosphamide, vincristine, and dacarbazine ('CVD-regimen'), which has previously been suggested for treatment of malignant pheochromocytomas.

METHODS

9 patients (5 males; age 55.0 ± 4.0 years) with MTC were enrolled. Prior to chemotherapy, progressive disease was established in all patients by use of WHO criteria. On day 1 of each cycle, patients started with cyclophosphamide 750 mg/m(2), vincristine 1.4 mg/m(2), and dacarbazine 600 mg/m(2); on day 2, patients received dacarbazine alone (600 mg/m(2)). Treatment cycles were repeated at 21-day intervals and 6 cycles were planned for each patient. The standard imaging procedure was computed tomography, and the primary end point was the objective tumor response rate. After chemotherapy, patients were followed up until progression.

RESULTS

9 patients underwent a total of 57 cycles (mean 6.3 ± 0.3 cycles). Treatment responses were: 0% complete response, 11% partial response, 56% stable disease, and 33% progressive disease. The median progression free survival was 13.6 months (range 5.8-24.2 months). The median change (baseline vs. end of treatment) of calcitonin was -19% (range -70% to +174%). Reversible myelosuppression and moderate gastrointestinal symptoms were the most common adverse events.

CONCLUSION

Although objective tumor response rates were low, the CVD regimen allowed disease stabilization for a substantial period of time and had acceptable toxicity. After initial surgery, chemotherapy may therefore be considered as a medical treatment option.

Transcriptional regulation by nonclassical action of thyroid hormone

Abstract

Thyroid hormone (TH) is essential for normal development, growth and metabolism. Its effects were thought to be principally mediated through triiodothyronine (T3), acting as a ligand for the nuclear TH receptors (TRs) α and β residing on thyroid hormone response elements (TREs) in the promoter of TH target genes. In this classical model of TH action, T3 binding to TRs leads to recruitment of basal transcription factors and increased transcription of TH responsive genes.

Recently, the concept of TH action on gene expression has become more diverse and now includes nonclassical actions of T3 and T4: T3 has been shown to activate PI3K via the TRs, which ultimately increases transcription of certain genes, e.g. HIF-1α. Additionally, both T3 and thyroxine (T4) can bind to a membrane integrin, αvβ3, which leads to activation of the PI3K and MAPK signal transduction pathways and finally also increases gene transcription, e.g. of the FGF2 gene. Therefore, these initially nongenomic, nonclassical actions seem to serve as additional interfaces for transcriptional regulation by TH. Aim of this perspective is to summarize the genes that are currently known to be induced by nonclassical TH action and the mechanisms involved.

Germline mutations of the TMEM127 gene in patients with paraganglioma of head and neck and extraadrenal abdominal sites

BACKGROUND

Hereditary pheochromocytoma is associated with germline mutations of a set of susceptibility genes to which the TMEM127 gene has recently been added. Patients with TMEM127 mutations have been thus far exclusively identified with adrenal tumors.

PATIENTS AND METHODS

A population-based series of 48 consecutive individuals from the European-American Pheochromocytoma Paraganglioma Registry with multiple paraganglial tumors and, of these, one extraadrenal paraganglial tumor were selected for this study. They all had normal results when screened for germline mutations of the genes RET, VHL, SDHB, SDHC, and SDHD. Germline mutation analysis of the TMEM127 gene included a search for intragenic mutations and large rearrangements.

RESULTS

Of the 48 eligible patients with extraadrenal paraganglial tumors, two (4.2%) were found to have TMEM127 mutations. One patient had multiple head and neck paraganglioma and one retroperitoneal extraadrenal and adrenal tumor.

CONCLUSION

TMEM127 germline mutations confer risks of extraadrenal paraganglial tumors in addition to the documented adrenal pheochromocytoma. Thus, surveillance for extraadrenal and adrenal paraganglial tumors is likely warranted in TMEM127 mutation carriers, although the true prevalence should be evaluated in patients with extraadrenal paraganglial tumors.

Stanniocalcin 1 induction by thyroid hormone depends on thyroid hormone receptor β and phosphatidylinositol 3-kinase activation

CONTEXT

Thyroid hormone (TH) mediated changes in gene expression were thought to be primarily initiated by the nuclear TH receptor (TR) binding to a thyroid hormone response element in the promoter of target genes. A recently described extranuclear mechanism of TH action consists of the association of TH-liganded TRβ with phosphatidylinositol 3-kinase (PI3K) in the cytosol and subsequent activation of the PI3K pathway.

OBJECTIVE

The aim of this study was to examine the effect of TH, TRβ and PI3K on stanniocalcin 1 (STC1) expression in human cells.

DESIGN

We treated human skin fibroblasts with triiodothyronine (T3) in the absence or presence of the PI3K inhibitor LY294002, a dominant negative PI3K subunit, Δp85α, and the protein synthesis inhibitor cycloheximide (CHX). The role of the TRβ was studied in cells from patients with resistance to thyroid hormone (RTH). STC-1 mRNA expression was measured by real-time PCR.

RESULTS

We found an induction of STC1 by T3 in normal cells, but less in cells from subjects with RTH (2.7 ± 0.2 vs. 1.6 ± 0.04, P < 0.01). The effect of T3 was completely abrogated by blocking PI3K with LY294002 (3.9 ± 0.5 vs. 0.85 ± 0.5; P < 0.05) and greatly reduced after transfection of a dominant negative PI3K subunit, demonstrating dependency on the PI3K pathway.

CONCLUSION

These results establish STC1 as a TH target gene in humans. Furthermore, we show that STC1 induction by TH depends on both TRβ and PI3K activation.