Bedeutung der TSH-Rezeptor-Antikörper für die Diagnose des Morbus Basedow sowie die Prognoseabschätzung der Schilddrüsenüberfunktion und der endokrinen Orbitopathie

[Commentary on the latest DGN procedure guidelines for radioiodine therapy for benign thyroid diseases]

Die aktuelle DGN-Handlungsempfehlung behandelt das Thema der Entwicklung der TRAK-Spiegel nach der Radiojodtherapie der Immunhyperthyreose erstmals im Vergleich zu den vorangehenden Versionen. Diese neuen Hinweise sollten differenziert eingeordnet und anschließend dem Patienten z.B. in den Aufklärungsunterlagen geeignet zugänglich gemacht werden. Bei der Verwendung fertiger kommerzieller Aufklärungsbögen, herausgegeben von einigen medizinisch orientierten Verlagsgesellschaften, ist auf deren Aktualität zu achten, ggf. sind die noch nicht berücksichtigten Aspekte im Einzelfall handschriftlich nachzutragen. Die Verwendung eigener klinikinterner Aufklärungsblätter zur Radiojodtherapie gutartiger Schilddrüsenerkrankungen bietet den Vorteil, dass neue Aspekte durch den behandelnden Nuklearmediziner selbst eingefügt werden können.

A dense mapping study of six European AITD susceptibility regions in a large Chinese Han Cohort of Graves' disease

OBJECTIVE

We aimed to investigate the six susceptibility loci of GD identified from European population in Chinese Han population and further to estimate the genetic heterogeneity of them in stratification of our GD patients.

DESIGN

Dense mapping studies based on GWAS.

PATIENTS

A total of 1536 GD patients and 1516 controls in GWAS stage and 1994 GD patients and 2085 controls and 5033 GD patients and 5389 controls in two replication stages.

MEASUREMENTS

Based on our previous GWAS data, independently GD-associated SNPs in each region were identified by TagSNP analysis and logistic regression analysis. The association of these SNPs was investigated in 1994 GD patients and 2085 controls, and then, the significantly associated SNPs (P < 0.05) were further genotyped in a second cohort including 5033 GD patients and 5389 controls.

RESULTS

After the first replication stage, four SNPs from three regions with P_first  < 0.05 were further selected and genotyped in another independent cohort. The association of two SNPs with GD was confirmed in combined Chinese cohorts: rs12575636 at 11q21 (P_combined  = 7.55 × 10^-11 , OR = 1.27) and rs1881145 in TRIB2 at 2p25.1 (P_combined  = 5.59 × 10^-8 , OR = 1.14). Further study disclosed no significant difference for these SNPs between GD subsets. However, eQTL data revealed that SESN3 could be a potential susceptibility gene of GD in 11q21 region.

CONCLUSIONS

Out of the six susceptibility loci of GD identified from European population, two risk loci were confirmed in a large Chinese Han population. There is variability in GD genetic susceptibility in different ethnic groups. SESN3 is a potential susceptible gene of GD in 11q21.

[Autoimmune diseases of the thyroid gland]

Autoimmune diseases of the thyroid gland are considered to be the most frequent cause of thyroid gland disorders. Autoimmune thyroid diseases consist of two subgroups: autoimmune thyroiditis (AIT) and Graves' disease. The AIT is the most common human autoimmune disease. Infiltration of the thyroid gland with cytotoxic T‑cells can lead to an initial thyrotoxicosis und during the course to hypothyroidism due to destruction of the thyroid gland. Substitution with Levothyroxine is indicated for manifest hypothyroidism and subclinical hypothyroidism with increased thyroid antibodies with the intention of normalizing the serum thyroid stimulating hormone (TSH). Graves' disease is characterized by the appearance of stimulating TSH receptor antibodies leading to hyperthyroidism. Endocrine ophthalmopathy may also occur. Ablative therapy with radioiodine therapy or thyroidectomy is administered to patients with Graves' disease without remission after at least 1 year of antithyroid drug therapy.

[Graves' ophthalmopathy]

Graves' orbitopathy (GO) is the main extrathyroidal manifestation of Graves' disease and the full clinical picture can impair the quality of life of the patients considerably. Active inflammation can often be effectively treated by intravenous steroids/immunosuppression, however does not lead to full remission, since inflammation rather quickly results in irreversible fibrosis and increase of orbital fat. Very important is the control of risk factors (smoking cessation, good control of thyroid function, selenium supplementation) to prevent progression to severe stages. Treatment should rely on a thorough assessment of activity and severity of GO. Rehabilitative surgery (orbital decompression, squint surgery, eyelid surgery) is needed in many patients to restore function and appearance. Anti-thyroid-stimulating hormone (TSH) receptor antibodies do specifically occur in these patients and correlate to the course of thyroid and eye disease. The levels of these antibodies can be used for treatment decisions at certain time points of the disease.

[Update on endocrine orbitopathy]

Graves' orbitopathy is an autoimmune disease of the ocular adnex connective tissue and most commonly occurs together with Grave's hyperthyroidism. Anti-TSH receptor antibodies are specific for Graves' disease and are related to both the course of thyroid and orbital diseases. An active inflammatory disease stage is followed by an inactive stage of incomplete remission in most patients. Periorbital swelling, proptosis, diplopia and lid retraction severely impair the patients' quality of life. In the active state anti-inflammatory treatment consists of i.v. steroids, off-label use of immunomodulatory medication, selenium and in emergency cases orbital decompression. Fortunately, defects in inactive stable Graves' orbitopathy can be successfully treated by surgery and involve decompression for proptosis reduction, muscle recession to correct diplopia and (finally) lid surgery.

Refined association of TSH receptor susceptibility locus to Graves' disease in the Chinese Han population

BACKGROUND

Convincing evidence has demonstrated the association of TSH receptor (TSHR) with Graves' disease (GD) in the Chinese Han population.

OBJECTIVE

The aim of this study was to identify the causal variants for GD in the region encompassing TSHR by a refining association study.

DESIGN AND METHODS

GD patients (1536) and 1516 sex-matched controls were recruited in the first stage, and an additional 3832 GD patients and 3426 sex-matched controls were recruited in the replication stage. Genotyping was performed using Illumina Human660-Quad BeadChips or TaqMan single nucleotide polymorphism (SNP) Genotyping Assays and the Fluidigm EP1 platform.

RESULTS

When the results of regression analysis for 74 genotyped SNPs and 922 imputed SNPs in the first-stage cohort were combined, rs179243 and rs3783949 were the probable susceptibility SNPs associated with GD in TSHR. Eleven SNPs, including rs179243 and rs3783949, were selected to further refine the association in the replication study. Finally, rs12101261 and rs179243 were confirmed as independent GD susceptibility variants in the replication and combined populations. Further, we also found that the rate of persistent TSHR autoantibody positivity (pTRAb+) was significantly higher in the GD patients with the susceptible genotypes rs12101261 or rs179243 than in the GD patients carrying the protective genotypes, after the GD patients had been treated for more than 1 year.

CONCLUSIONS

These findings indicate that rs12101261 and rs179243 are the possible causal SNPs for GD susceptibility in the TSHR gene and could serve as genetic markers to predict the outcome of pTRAb+ in GD patients.

[Hyperthyroidism]

Thyrotoxicosis is mainly caused by autonomous adenomas of the thyroid gland and by Graves' disease. A less frequent cause for thyrotoxicosis is Hashimoto's thyroiditis. Thyrotoxicosis in autonomous adenomas and Graves' disease is caused by an increased thyroid hormone production whereas hyperthyroidism in Hashimoto's thyroiditis results from destruction of the thyroid gland. Drug therapy depends on the cause of the disease. Autonomous adenomas and Graves' disease are treated with methimazole and potentially with β-blockers. Regarding thyroid ablative therapy, radioiodine is mostly preferred compared to thyroidectomy. Drug therapy of Hashimoto's thyroiditis is purely symptomatic using β-blockers and rarely corticosteroids. Hyperthyroidism in pregnancy is a major issue and pregnant women in the first trimester are treated with propylthiouracil (PTU) whereas women in the second and third trimesters are treated with methimazole. The aim is to maintain the serum fT4 levels within the upper normal range.

Surgical treatment of Graves' ophthalmopathy

The aims of surgical treatment in Graves's orbitopathy (GO) are improvement of function and appearance. Since antiinflammatory treatment of GO rarely results in a complete resolution of symptoms, surgical treatment is very important for patients well being. Rehabilitative surgery includes orbital decompression, squint correction, lid lengthening and blepharoplasty and these procedures have to be performed in centres of expertise. Various techniques have been developed for orbital decompression which allow now a graded approach to proptosis reduction and optic nerve decompression in emergency situations. Extraocular muscle recessions can be successfully performed to treat most of the patients with diplopia. Only large or complex squint angles are difficult to treat and step by step procedures are recommended in these patients. Lid lengthening procedures are performed most often in GO patients and should be performed under local anaesthesia to get a good result. Serious complications are rare.

[Graves' ophthalmopathy from the internist's perspective]

Graves' orbitopathy (GO) is the most frequently observed extrathyroidal manifestation of Graves' disease occurring in up to 40% of patients. Most patients with Graves' orbitopathy are tested positive for TSH receptor autoantibodies (TRAb), which are pathognomonic for Graves' disease and also play a central pathogenetic role in the development of GO. For the diagnosis of Graves' disease, symptoms of hyperthyroidism, low TSH and high fT3 and/or fT4 levels and positive TRAbs are typical. All patients with Graves' disease must be regularly examined for extrathyroidal manifestations, especially for Graves' orbitopathy. For hyperthyroidism, treatment with antithyroidal drugs, such as thiamazole or propylthiouracil is initiated to quickly restore euthyroidism, which also frequently leads to improvement of Graves' orbitopathy. Smoking cessation is also heavily mandated. In cases of relapse or ineffective antithyroidal treatment, radioiodine therapy or thyroid surgery is a further definitive therapeutic option to treat hyperthyroidism. The management of Graves' orbitopathy remains clinically challenging and demands involvement of a multidisciplinary team including endocrinologists, ophthalmologists, surgeons, radiotherapists and nuclear medicine specialists.

Clinical review about TRAb assay's history

Commercial assays to measure thyroid stimulating hormone (TSH) receptor (TSHR) autoantibodies (TRAb) have been available for the serological diagnosis of autoimmune thyroid diseases (AITD) for several years. The widespread assessment of this parameter has identified Graves' disease (GD) as a common organ-specific autoimmune disease. Within the present article we aim to review immunobiological and epidemiological aspects as well as diagnostic methods available for the detection of TRAb. Over the last decade, TRAb detection in GD became more sensitive since TRAb assays were being largely improved by named research groups. Therefore, functional assay (fas) and diagnostic sensitivity of current TRAb assays will be discussed. Within the second part of this review we will focus on clinical applications of TRAb measurement for outcome prediction of GD as well as the importance of this method to distinguish GD from other AITD.

[Update hyperthyreoidism]

Hyperthyroidism is mainly caused by Graves' disease and toxic adenoma or multinodular goiter. In Europe, treatment of both disorders is usually started with antithyroidal drugs such as methimazole. Complications include agranulocytosis and the risk is dose-dependent. The starting dose of methimazole should not exceed 15-20 mg/d. Propylthiouracil can cause severe liver failure, leading to liver transplantation or death. Propylthiouracil, therefore, should not be used as first line agent and is only recommended when an antithyroid drug is to be started during the first trimester of pregnancy or in individuals who have experienced adverse responses to methimazole. Toxic adenoma is finally treated with radioioidine. To reduce the risk of treatment failure, antithyroidal drugs should be stopped at least one week prior to radioiodine. For Graves' disease, remission is unlikely if antibodies against the TSH-receptor remain above 10 mU/l after 6 months of antithyroidal treatment and radioiodine or thyroidectomy can be recommended. Thyroidectomy should be performed as (near) total thyreoidectomy.

[Graves' ophthalmopathy]

Graves' orbitopathy is part of an autoimmune systemic disease which compiles hyperthyroidism, orbitopathy, dermopathy and acropachy. Stimulating antibodies against the TSH receptor play the central pathogenetic role. Main symptoms of Graves' orbitopathy comprise soft tissue inflammation, proptosis impairment of ocular motility and lid retraction. Inflammatory reactions of orbital fibroblasts are responsible for the symptoms. To restrict damage anti-inflammatory therapy (mainly systemic steroids, orbital irradiation) is indicated in moderate to severe active disease stages, and surgical orbital decompression in sight threatening states. In mild cases expectant strategy and selenium administration is sufficient. In inactive disease stages surgery is performed to improve appearance and function. Restoring euthyroidism leads to improvement of Graves' orbitopathy in about 60% of the patients. Radioiodine therapy without glucocorticoids is associated with a small but significant risk (15%) of deterioration or relapse. Thyroidectomy is neutral in later stages but may improve Graves' orbitopathy in early active stages.