Utilização dos testes de função tireoidiana na prática clínica

Abstract

Laboratory tests are essential for the accurate diagnosis and cost-effective monitoring of thyroid dysfunction. Hormone levels can only confirm a diagnosis when there is a high level of clinical suspicion. For most patients, symptoms are nonspecific and subtle, so biochemical tests are necessary to identify the disorder. The purpose of this article is to critically analyze the use of standard thyroid function tests, which include measuring the levels of serum thyroid-stimulating hormone (TSH), thyroid hormones and antithyroid antibodies. The pitfalls of and impediments to the routine use of these tests are discussed based on a Medline database survey, and recommendations are presented to optimize the use of these diagnostic tools in clinical practice. RESUMOExames laboratoriais são fundamentais para o diagnóstico acurado e o monitoramento custo--efetivo das disfunções tireoidianas. Quando há alta suspeita clínica, as dosagens hormonais apenas confirmam o diagnóstico. No entanto, na maioria dos pacientes, a sintomatologia é sutil e inespecífica, de forma que apenas testes bioquímicos podem detectar o transtorno. O objetivo deste artigo é fazer uma análise crítica do uso apropriado dos principais testes de função tireoidiana, entre eles a dosagem sérica do hormônio estimulante da tireoide (TSH), dos hormônios tireoidianos e dos anticorpos antitireoidianos. Mediante um levantamento na base de dados do Medline, são discutidas as principais armadilhas e interferências relacionadas ao uso cotidiano desses testes e são apresentadas recomendações para otimizar a utilização dessas ferramentas diagnósticas na prática clínica. Arq Bras Endocrinol Metab. 2013;57(3):193-204

Thyroid Autoimmunity: Role of Anti-thyroid Antibodies in Thyroid and Extra-Thyroidal Diseases

“…Anti-TSHR antibodies are found in 90% of GD patients, 0–20% HT, and 10–75% of atrophic thyroiditis patients (9). Other studies noted TSHR antibodies in around 10% of HT patients (10, 11).…”

“…However, their contribution to thyroid damage compared to T cell and cytokine-mediated apoptosis is minor (28). Anti-TPO antibodies are detected in 90–95% of AITD patients, 80% of GD, and 10–15% of non-AITD patients (9). While anti-TPO antibodies may act cytotoxic on thyrocytes in HT they do not have an established role in GD (29).…”

“…Among HT patients, antibody prevalence was 60–80% and in 50–60% in GD patients. Another study identified anti-Tg antibodies in 70–80% of AITD patients, 30–40% of GD patients, and 10–15% of patients with non-thyroid immune disorders (9). Anti-Tg antibodies can cross the placenta barrier, but the effect on the neonate is unclear (21).…”

Farmacêutico bioquímico: uma abordagem voltada para o TSH e doenças da tireoide

“…Entretanto, quando há uma grande suspeição clínica, as dosagens hormonais apenas confirmarão o diagnóstico. Todavia, em grande parte dos pacientes, a sintomatologia é sutil e não específica, relatando que só é possível, por testes bioquímicos, detectar o transtorno presente (6).…”

The Comparison of the Performance of a Second (Fast TSH) and Third (HYPERsensitive TSH) Generation Autometed TSH Immunassays in Healthy Euthyroid Subjects

“…The lowest detection limits of the first, which are not used nowadays, and second generation TSH kits were 1-2 µIU/mL and 0.1-0.2 µIU/mL, respectively. The lowest detection limits of the third and fourth generation TSH kits were 0.01-0.02 µIU/mL and 0.001-0.002 µIU/mL, respectively (7)(8)(9). Both third and fourth generation (ultrasensitive) TSH kits can be used as thyroid function screening tests in routine clinical laboratories (10).…”