The terminology of TSH- receptor antibodies (Table 1) has evolved from the methods used for their measurement. In essence there are two current methods: the binding assay, which measures the capacity of immunoglobulins to inhibit the binding of labelled TSH (or a labelled monoclonal TSH- receptor antibody) to puri fied or recombinant TSH receptor; and bioassays which measure the stimulatory or inhibitory effects of immunoglobulins on some aspect of thyroid cell function. Generally, cyclic AMP production is used as the endpoint in bioassays, but there has been an irreversible move away from using primary cultures of animal or human thyroid cells in these assays, with their attendant problems of supply and standardization, to using either cell lines, such as rat FRTL- 5 cells, or Chinese hamster ovary cells transfected with TSH receptor. With the most sensitive bioassays for TSH- receptor- stimulating antibodies almost all patients with Graves’ disease are positive, but these antibodies are rarely found in the absence of Graves’ disease, and then are associated with a greatly increased risk of future hyperthyroidism. This is shown most clearly by the finding that 30– 50% of euthyroid patients with thyroid- associated ophthalmopathy have TSH- receptor antibodies, and this proportion increases if the most sensitive assays are used; the majority of these patients subsequently develop hyperthyroidism.

Table1. Nomenclature and assay of the major types of TSH- receptor antibodies

As would be predicted, there is only a weak correlation between levels of TSH- receptor antibodies measured in the binding and stimulatory bioassays. Current binding assays have a greater than 95% sensitivity and specificity for the diagnosis of Graves’ disease but these antibodies must be used with knowledge of the clinical context. For instance, 10% of patients with autoimmune hypothyroidism will have TSH- receptor blocking antibodies that will be detected as positive in the binding assay, but the thyroid status makes the interpretation of the result clear. Neutral antibodies with binding but not biological activity may also be detected. Antibodies against the TSH receptor are present at much lower concentrations than thyroid peroxidase antibodies and this makes the development of robust and simple solid- phase assays very difficult, compounded by problems in expressing the TSH receptor in its native form.

TSH- receptor antibody testing is not necessary for the diagnosis of Graves’ disease when this is clinically obvious, for instance because there is coincident ophthalmopathy, or when such information will not influence management, for instance if the decision has already been made to proceed with radioiodine treatment. However, as the cost and precision of TSH- receptor binding assays are now reasonable, there is an increasing tendency to use these assays to diagnose Graves’ disease in cases where determining the aetiology of hyperthyroidism is required, and to rule out destructive thyroiditis. Other diagnostic tools (such as measurement of thyroid peroxidase antibodies or thyroid iodine uptake, or performing a thyroid scan) are either less convenient to undertake or less specific and sensitive. Prediction of outcome after antithyroid drugs has been another frequently suggested use for these assays, but although there is no doubt that the presence of high levels of TSH- receptor antibodies before treatment, or detectable levels after treatment, is associated with a higher rate of relapse, the sensitivity and specificity of these measurements are too poor to be used alone routinely in clinical practice. However, when pretreatment serum TSH- binding inhibiting immunoglobulins (TBII) is combined with other measurements (age, goitre size, and HLA/ PTPN22 genotype), a score can be generated which has better predictive value.

The one clear situation where measurement of TSH- receptor antibodies is definitely indicated is during pregnancy in Graves’ dis ease: a high level of maternal antibodies is a strong predictor of neo natal thyrotoxicosis, which occurs in 1– 5% of women with Graves’ disease who become pregnant. Current recommendations are that TSH- receptor antibody measurement should be made in early pregnancy in (i) women taking an antithyroid drug for Graves’ disease, and (ii) women with a history of Graves’ disease successfully treated by radioiodine or surgery. Measurement should be repeated at 18– 22 weeks in (i) those still requiring an antithyroid drug to maintain euthyroidism, and (ii) those who were antibody- positive after surgery or radioiodine on initial screening; further tests in later pregnancy as well as fetal monitoring are required in those women who are positive for TSH- receptor antibodies at this stage.

اخر الاخبار

اخبار العتبة العباسية المقدسة

قسم المعارف يواصل دعم الحركة الثقافية بإصدارات متنوِّعة عَبرَ معرض الكتاب الدائم

إقبال نسوي واسع على منافذ التبرع في العتبة العباسية المقدسة لدعم الشعبين الإيراني واللبناني

العتبة العباسية المقدسة تباشر تنفيذ المرحلة الثالثة من أعمال التوسعة

بمحافظة ذي قار.. قسم الشؤون الفكرية يقيم ندوة معرفية عن دور بصيرة العلماء في سلامة المجتمع

المزيد

الآخبار الصحية

سرّ بسيط لصحة القلب.. أطعمة تخفض الكوليسترول خلال أسابيع

سبب خفي لإعتام عدسة العين ؟

عوامل خفية تسرّع شيخوخة الدماغ

أسباب الرغبة الشديدة في تناول الحلويات والأطعمة النشوية

المزيد

الآخبار التكنلوجية

كندا تصنع كاسحة جليد من جيل جديد

رواد "أرتيميس 2" يكشفون تفاصيل حياتهم في الفضاء

حفريات صينية تكشف كائنات بحرية عاشت قبل 546 مليون عام

روسيا تطلق صاروخ "سويوز-2.1 إيه" من قاعدة بليسيتسك الفضائية

المزيد

مواضيع ذات صلة

Thyroglobulin and Thyroid Peroxidase Antibodies

Interpretation of Serologic Tests

Features of the Humoral Immune Response Useful in Diagnostic Testing

Enzyme Immunoassays

Immunofluorescent assays

Particle Agglutination

Precipitation Tests

Production of Antibodies for use in Laboratory Testing

Investigation of Strain Relatedness/Pulsed-Field Gel Electrophoresis

Detection of Antimicrobial Resistance

The Light Microscope

Identification of Microorganisms Grown in Culture