RESUMO
OBJECTIVE: Postpartum thyroid dysfunction (PPTD) is an autoimmune disorder characterized by the development of transient hyperthyroidism and, more frequently, hypothyroidism (or both) during the first six months of the puerperal period. A variable incidence has been reported in part because of differences in the number of women studied, the frequency of thyroid assessment postpartum, diagnostic criteria and methodology. The aim of this study was to evaluate thyroid function, ultrasound images and titre of autoantibodies against thyroid antigens in a cohort of pregnant women who met the criteria of 'normal' thyroid gland structure on clinical examination and imaging and normal thyroid function tests without a significantly positive anti-thyroid peroxidase (TPO) antibody titre (i.e. < 100 U/ml) in the first trimester. DESIGN AND PATIENTS: Eight hundred nulliparous or multiparous (one to seven previous pregnancies) pregnant women (age 26.1 +/- 4.8 years, mean +/- SD), were submitted to clinical, laboratory and ultrasonographic examination in the first trimester of pregnancy. Among these forty-six patients were excluded because of thyroid dysfunction, ultrasound structural abnormalities or a positive anti-TPO antibody titre (> 100 U/ml). A total number of 754 women were available for further studies in the postpartum period. A relatively large number of these patients (386) were lost for follow-up either before or after delivery. MEASUREMENTS: A cohort of 368 puerperal women was followed up regularly at 3, 6, 12 and 24 months after delivery, with periodic thyroid function tests, random urine iodine measurements, assays for serum autoantibodies against thyroid antigens and imaging by ultrasound. RESULTS: The provisional diagnosis of PPTD was established in 78 out of 368 who had positive anti-TPO levels and ultrasonographic thyroid structural changes. Twenty-nine of these patients had a transient rise of anti-TPO autoantibodies characterizing an autoimmune reaction. These autoantibodies levels progressively declined or became negative. Moreover none of these patients had evidence for altered thyroid function during the 18-24 months of follow-up. The remaining 49 patients (13.3%) progressively developed thyroid function abnormalities (mainly hypothyroidism) indicating the presence of thyroid gland changes due to PPTD. Further follow-up studies indicated that at 18-24 months, 42 patients had serum levels of anti-TPO-Ab that were more elevated, as compared with the first year values. Predictive factors found during pregnancy for developing PPTD were: (1) relatively low levels of anti-TPO, between 60 and 100 U/ml (odds ratio 3.1 : 1), and (2) ultrasonographic thyroid structural changes in the first trimester (odds ratio 6.4 : 1). CONCLUSIONS: We conclude that the prevalence of postpartum thyroid dysfunction in our geographical area ranges from 6.7% to 13.3%, considering, respectively, all pregnant women that were examined (n = 754) or only the number of puerperal women actually followed-up (n = 368). A transient form of thyroid autoimmune reaction characterized by elevated serum levels of anti-TPO that progressively declined or disappeared was observed in 29 puerperal women. Sonographic structural and echogenicity changes in the thyroid gland and borderline positive anti-TPO levels (between 60 and 100 U/ml) during pregnancy were considered to be of predictive value for development of postpartum thyroid dysfunction.
Assuntos
Doenças Autoimunes/epidemiologia , Transtornos Puerperais/epidemiologia , Doenças da Glândula Tireoide/epidemiologia , Adolescente , Adulto , Autoanticorpos/sangue , Doenças Autoimunes/diagnóstico , Brasil/epidemiologia , Feminino , Seguimentos , Humanos , Valor Preditivo dos Testes , Gravidez , Prevalência , Transtornos Puerperais/diagnóstico , Fatores de Risco , Tireoglobulina/sangue , Doenças da Glândula Tireoide/diagnóstico , Testes de Função Tireóidea , Glândula Tireoide/diagnóstico por imagem , Glândula Tireoide/imunologia , Hormônios Tireóideos/sangue , UltrassonografiaRESUMO
Anti-Gal is a human polyclonal antibody that constitutes approximately 1% of the circulating immunoglobulin G (IgG), interacts specifically with the mammalian carbohydrate alpha-galactosyl epitope. Furthermore, it was found to mimic in vitro thyrotropin (TSH) effects regarding stimulation for cyclic adenosine monophosphate (cAMP) synthesis, 125I uptake, and cellular proliferation on cultured porcine thyrocytes and on Graves' disease thyrocytes, but not on normal human thyrocytes. As immune activation in sporadic and endemic goiters might play a secondary role in regulating thyrocyte proliferation and function, we evaluated anti-Gal titers in endemic goiter. Serum was obtained from 109 Chagas'-negative patients living in an endemic goiter area of Brazil (Grao Mogol, MG) and 160 controls. The patients were divided into 3 groups, according to their goiter size (World Health Organization [WHO] classification): grade 0 (group 1, n = 24), grade I-II (group 2, n = 41), and grade III-IV (group 3, n = 44). Anti-Gal was assessed by a radioimmunological procedure (results expressed as the percentage of bound radioactivity/total activity [%B/T]). The antibody titer was significantly more elevated in group 1 (mean +/- SEM: 9.27%+/-0.80%), in group 2 (mean +/- SEM: 16.17%+/-0.97%), and in group 3 (20.97%+/-1.30%) than in normal controls (6.46%+/-0.33%). Analysis of the male and female data separately for anti-Gal titer did not substantially alter these results. We concluded that the anti-Gal titer is higher in patients with endemic goiter and presented a possible relationship with the size of goiter. Whether these antibodies contribute to the pathogenesis of the disease needs further clarification.