Recent recommendations from ATA guidelines to define the upper reference range for serum TSH in the first trimester match reference ranges for pregnant women in Rio de Janeiro

ABSTRACT Objectives: American Thyroid Association (ATA)'s new guidelines recommend use of population-based trimester-specific reference range (RR) for thyrotropin (TSH) in pregnancy. The aim of this study was to determine first trimester TSH RR for a population of pregnant women in Rio de Janeiro State. Subjects and methods: Two hundred and seventy pregnant women without thyroid illness, defined by National Academy of Clinical Biochemistry, and normal iodine status were included in this sectional study. This reference group (RG) had normal median urinary iodine concentration (UIC = 219 μg/L) and negative anti-thyroperoxidase antibodies (TPOAb). Twin pregnancy, trophoblastic disease and use of drugs or supplements that influence thyroid function were excluded. In a second step, we defined a more selective reference group (SRG, n = 170) by excluding patients with thyroiditis pattern on thyroid ultrasound and positive anti-thyroglobulin antibodies. This group also had normal median UIC. At a final step, a more selective reference group (MSRG, n = 130) was defined by excluding any pregnant women with UIC < 150 μg/L. Results: In the RG, median, 2.5th and 97.5th percentiles of TSH were 1.3, 0.1, and 4.4 mIU/L, respectively. The mean age was 270 ± 5.0 and the mean body mass index was 25.6 ± 5.2 kg/m2. In the SRG and MSRG, 2.5th and 975th percentiles were 0.06 and 4.0 (SRG) and 0.1 and 3.6 mIU/L (MSRG), respectively. Conclusions: In the population studied,TSH upper limit in the first trimester of pregnancy was above 2.5 mIU/L. The value of 3.6 mIU/L, found when iodine deficiency and thyroiditis (defined by antibodies and ultrasound characteristics) were excluded, matches recent ATA guidelines.

Reference interval for thyrotropin in a ultrasonography screened Korean population

BACKGROUND/AIMS: The diagnostic accuracy of thyroid dysfunctions is primarily affected by the validity of the reference interval for serum thyroid-stimulating hormone (TSH). Thus, the present study aimed to establish a reference interval for TSH using a normal Korean population. METHODS: This study included 19,465 subjects who were recruited after undergoing routine health check-ups. Subjects with overt thyroid disease, a prior history of thyroid disease, or a family history of thyroid cancer were excluded from the present analyses. The reference range for serum TSH was evaluated in a normal Korean reference population which was defined according to criteria based on the guidelines of the National Academy of Clinical Biochemistry, ultrasound (US) findings, and smoking status. Sex and age were also taken into consideration when evaluating the distribution of serum TSH levels in different groups. RESULTS: In the presence of positive anti-thyroid peroxidase antibodies or abnormal US findings, the central 95 percentile interval of the serum TSH levels was widened. Additionally, the distribution of serum TSH levels shifted toward lower values in the current smokers group. The reference interval for TSH obtained using a normal Korean reference population was 0.73 to 7.06 mIU/L. The serum TSH levels were higher in females than in males in all groups, and there were no age-dependent shifts. CONCLUSIONS: The present findings demonstrate that the serum TSH reference interval in a normal Korean reference population was higher than that in other countries. This result suggests that the upper and lower limits of the TSH reference interval, which was previously defined by studies from Western countries, should be raised for Korean populations.

Utilização dos testes de função tireoidiana na prática clínica / The clinical use of thyroid function tests

Exames 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 apresentadas recomendações para otimizar a utilização dessas ferramentas diagnósticas na prática clínica.

Laboratory tests are essential for accurate diagnosis and cost-effective management of thyroid disorders. When the clinical suspicion is strong, hormonal levels just confirms the diagnosis. However, in most patients, symptoms are subtle and unspecific, so that only biochemical tests can detect the disorder. The objective of this article is to do a critical analysis of the appropriate use of the most important thyroid function tests, including serum concentrations of thyrotropin (TSH), thyroid hormones and antithyroid antibodies. Through a survey in the MedLine database, we discuss the major pitfalls and interferences related to daily use of these tests and recommendations are presented to optimize the use of these diagnostic tools in clinical practice.

Pruebas de función tiroidea

Las pruebas de función tiroidea se han convertido en pruebas de rutina en los laboratorios clínicos, así como de común solicitud en las ordenes médicas, lo que hace necesario que los médicos tengan un dominio amplio y útil de las diferentes pruebas y técnicas que se utilizan para evaluar función tiroidea. La mejor comprensión de la fisiología y metabolismo de las hormonas T3 y T4, ha hecho que desde hace algunos años se venga haciendo énfasis en la mayor utilidad y especificidad de las fracciones libres, lo que ha mejorado el diagnóstico y seguimiento de los pacientes y ha llevado a una mejor utilización e interpretación del comportamiento de éstas en el paciente con una determinada enfermedad tiroidea. Se ha definido también la importancia de los anticuerpos, muy especificamente en las enfermedades tiroideas que tienen un componente autoinmune. Estas pruebas deben hacer parte de las pruebas de rutina solicitadas en la evaluación de los pacientes con afecciones tiroideas.