The sonographic appearances in postpartum thyroiditis

Thyroid dysfunction following pregnancy and implications for breastfeeding

Subclinical autoimmune thyroiditis exacerbates after delivery through immune rebound mechanisms and results in 5 types of thyroid dysfunction. The prevalence of postpartum thyroid dysfunction is around 5% in mothers in the general population. Typically, an exacerbation induces destructive thyrotoxicosis followed by transient hypothyroidism, known as postpartum thyroiditis. Late development of permanent hypothyroidism is found frequently and patients should be followed up once every one to two years. Destructive thyrotoxicosis in postpartum thyroiditis should carefully be differentiated from post-partum Graves' disease. Postpartum thyroiditis typically occurs 1-4 months after parturition whereas Graves' disease develops at 4-12 months postpartum. Anti-TSH receptor antibodies (TRAb) are typically positive and thyroid blood flow is high in Graves' disease, whereas these features are absent in postpartum thyroiditis. Postpartum Graves' disease should be treated with antithyroid drugs.

Risk Factors for Postpartum Thyroid Dysfunction in Euthyroid Women Prior to Pregnancy

BACKGROUND

Thyroid dysfunction is common during the postpartum and the predisposing factors for its development are considered specific for the population studied. The aim of this study was to evaluate the risk factors for the occurrence of postpartum thyroid dysfunction (PPTD) in euthyroid women prior to pregnancy.

MATERIALS AND METHODS

Forty-five women with PPTD and 55 age-matched euthyroid postpartum women from Plovdiv, Bulgaria were included in the study. TSH, FT4, FT3, TPOAb, TgAb, TRAb were measured and ultrasound evaluation of the thyroid was performed in the first trimester of pregnancy and during the postpartum.

RESULTS

The study found higher risk of developing PPTD in women with family history of thyroid disease (OR 4.42; 95% CI 1.87,10.43), smokers (OR 4.01; 95% CI 1.72,9.35), personal history of autoimmune thyroid disease (OR 5.37; 95% CI 1.15,28.53), positive TPOAb (OR 18.12; 95% CI 4.93,66.65) and thyroid US hypoechogenicity during early pregnancy (OR 6.39; 95% CI 2.53,16.12) and those who needed levothyroxine during pregnancy (OR 3.69; 95% CI 1.28,10.61). BMI before pregnancy was significantly lower in women with PPTD than in euthyroid postpartum women (22.80±0.55 vs 26.25±0.97, p=0.013). The multivariate logistic regression analysis identified as most important independent risk factors for PPTD occurrence the TPOAb positivity during early pregnancy, family history of thyroid disease, smoking and lower BMI before pregnancy.

CONCLUSION

Our data suggest that in the population studied several factors are associated with an increased risk of PPTD and screening for thyroid disorders among those women can be beneficial.

Acoustic Structure Quantification Analysis of the Thyroid in Patients with Diffuse Autoimmune Thyroid Disease

The aim of this study was to assess whether acoustic structure quantification (ASQ) can differentiate normal from pathological thyroid parenchyma in patients with diffuse autoimmune thyroid disease (AITD). We evaluated 83 subjects (72 [87%] women and 11 [13%] men) aged 19 to 94 years with a mean age of 53 years. We performed a prospective study (from March 2011 to November 2014) that included 43 (52%) patients with chronic autoimmune thyroiditis (CAT), 22 (26%) patients with Graves' disease (GD), and 18 (22%) healthy volunteers. The ASQ values were significantly lower in normal subjects than in subjects with CAT and GD (p < 0.001). In contrast, the differences between the GD and the CAT patients (p = 0.23) were not statistically significant. The optimal cutoff ASQ value for which the sum of sensitivity and specificity was the highest for the prediction of diffuse thyroid pathology was 103 (95% confidence interval = [0.79, 0.95]). At this cutoff value, the sensitivity was 83% and the specificity was 89%. Our findings suggest that ASQ is a useful method for the assessment of the thyroid in patients with AITD.

Ultrasonographic characteristics and follow-up in post-partum thyroiditis

Post-partum thyroiditis (PPT) is an autoimmune disorder of the thyroid gland, which occurs in the first year after parturition. This study was designed to evaluate sonographic characteristics in a group of PPT patients in Tehran. The study group consisted of 119 PPT patients and 97 normal post-partum women as the control group. Physical examination of thyroid and ultrasonography were carried out monthly in PPT patients until remission for up to 12 months post-partum and 65 patients were followed-up until the end of the study. Visible goiter was detected in 21.8% of patients and 6.7% of the control group (p < 0.001). Hypoechogenecity in thyroid sonography was present in 98.5% of patients and 7% of the control group (p < 0.001). Initially mean thyroid volume in PPT patients was found to be 77% more than that of the control group. After remission, mean thyroid volume decreased by 25% in PPT patients. At 12 months after delivery, only 6 patients had abnormal thyroid function tests, while 4 patients with TSH > 10 mU/I still showed hypoechogenicity in thyroid sonography. In conclusion, sonography may be recommended as an adjuvant to laboratory tests in evaluation of PPT patients.

The spectrum of postpartum thyroid dysfunction: diagnosis, management, and long-term prognosis

OBJECTIVE

To provide an overview of thyroid abnormalities that can occur after delivery.

METHODS

We review the diagnosis and management of various types of postpartum thyroid dysfunction.

RESULTS

A common problem during the postpartum period, thyroid dysfunction is found in approximately 5% of new mothers in the general population. Such thyroid dysfunction can manifest in various forms (hyperthyroid or hypothyroid, transient or persistent), each of which necessitates different treatment. The most common type of thyroid dysfunction is destructive thyrotoxicosis, which is due to the aggravation of autoimmune thyroiditis. It occurs at 1 to 3 months after delivery as sudden thyrotoxicosis and lasts for 1 to 3 months, after which transient hypothyroidism may ensue in some cases. Simply symptomatic treatment may be sufficient for such transient thyroid dysfunctions. Postpartum Graves' disease is found in approximately 11% of the cases of postpartum thyroid dysfunction. Graves' hyperthyroidism usually occurs at 3 to 6 months after parturition. In the treatment of postpartum Graves' disease, one may choose radioactive iodine, antithyroid drugs, or surgical therapy; however, transient Graves' hyperthyroidism, which often occurs in patients with postpartum Graves' disease, may require neither radioactive iodine therapy nor thyroidectomy. Mothers at high risk for development of postpartum thyroid dysfunction can be screened by testing for antimicrosomal antibodies. Although a strong correlation exists between the presence of antimicrosomal antibodies and postpartum thyroid dysfunction, the cost-effectiveness of screening for postpartum autoimmune thyroid syndrome remains controversial.

CONCLUSION

For optimal management of the postpartum conditions of Graves' disease, destructive thyrotoxicosis, and hypothyroidism, the clinician should be aware of diagnostic techniques that will facilitate early intervention or will prompt careful surveillance.

Postpartum thyroiditis

Postpartum thyroiditis (PPT) is the occurrence, in the postpartum period, of transient hyperthyroidism and/or transient hypothyroidism, with most women returning to the euthyroid state by 1 year postpartum. The prevalence of PPT varies from 1.1 to 16.7%, with a mean prevalence of 7.5%. Women with type I diabetes mellitus have a three-fold increase in the prevalence of PPT. PPT is an autoimmune disorder which is a transient form of Hashimoto's thyroiditis occurring postpartum as a consequence of the immunologic flare following the immune suppression of pregnancy. Women experience symptoms in both the hyperthyroid and hypothyroid phase, but the association between PPT and postpartum depression remains undefined. Approximately 25% of women with a history of PPT will develop permanent hypothyroidism in the ensuing 10 years. Treatment for the hyperthyroid phase, when required, is a short dose of beta-blockers. Women with a TSH greater than 10 mU/l, or between 4 and 10 mU/l with symptoms or attempting pregnancy, require thyroid hormone replacement. Whether or not to screen for PPT remains controversial.

Postpartum thyroiditis and autoimmune thyroiditis in women of childbearing age: recent insights and consequences for antenatal and postnatal care

Postpartum thyroiditis is a syndrome of transient or permanent thyroid dysfunction occurring in the first year after delivery and based on an autoimmune inflammation of the thyroid. The prevalence ranges from 5-7%. We discuss the role of antibodies (especially thyroid peroxidase antibodies), complement, activated T cells, and apoptosis in the outbreak of postpartum thyroiditis. Postpartum thyroiditis is conceptualized as an acute phase of autoimmune thyroid destruction in the context of an existing and ongoing process of thyroid autosensitization. From pregnancy an enhanced state of immune tolerance ensues. A rebound reaction to this pregnancy-associated immune suppression after delivery explains the aggravation of autoimmune syndromes in the puerperal period, e.g., the occurrence of clinically overt postpartum thyroiditis. Low thyroid reserve due to autoimmune thyroiditis is increasingly recognized as a serious health problem. 1) Thyroid autoimmunity increases the probability of spontaneous fetal loss. 2) Thyroid failure due to autoimmune thyroiditis-often mild and subclinical-can lead to permanent and significant impairment in neuropsychological performance of the offspring. 3) Evidence is emerging that as women age subclinical hypothyroidism-as a sequel of postpartum thyroiditis-predisposes them to cardiovascular disease. Hence, postpartum thyroiditis is no longer considered a mild and transient disorder. Screening is considered.

Aspectos ultra-sonográficos e prevalência da tireoidite pós-parto em gestantes sem disfunção tireóidea atendidas em hospital público de São Paulo

Avaliamos prospectivamente a função, as imagens ultra-sonográficas e a auto-imunidade tireóidea em grupo racial heterogêneo de 800 mulheres grávidas, primíparas ou multíparas (1 a 7 gestações prévias) atendidas em hospital universitário de São Paulo durante o pré-natal. Quarenta e seis pacientes foram excluídas do estudo por apresentarem diagnóstico confirmado de doença tireóidea anterior; das 754 restantes, 386 abandonaram o seguimento antes ou após o parto. Assim, a coorte avaliada no puerpério constituiu-se de 368 puérperas, examinadas aos 3, 6, 12 meses e no 2º ano pós-parto. Embora 29 pacientes tenham tido aumento transitório daqueles anticorpos antitireóideos, caracterizando reação de auto-imunidade, estes progressivamente declinaram ou tornaram-se negativos durante o puerpério. Entretanto, nenhuma destas evoluiu com disfunção tireóidea durante o acompanhamento. Quarenta e nove pacientes (13,3%) desenvolveram progressivamente alterações funcionais da tireóide (principalmente hipotireoidismo), provavelmente devido à TPP. Além disso, a continuação do seguimento mostrou que em 18 a 24 meses, 42 mostraram níveis séricos de anti-TPO mais elevados, em comparação aos valores do primeiro ano. Os fatores de risco para o desenvolvimento da TPP, presentes durante a gravidez, foram: (1) níveis relativamente baixos de anti-TPO, entre 60 e 100U/mL [risco relativo ou odds ratio de 3,1] e (2) alterações estruturais ultra-sonográficas da tireóide no primeiro trimestre [odds ratio de 6,4]. Concluímos que a prevalência de TPP em hospital público de São Paulo foi de 13,3%, considerando as 368 pacientes seguidas. Em 29 puérperas foi diagnosticada forma transitória de reação tireóidea auto-imune, caracterizada por elevação dos níveis séricos de anti-TPO, que posteriormente regrediram.

Postpartum thyroid dysfunction in women with normal thyroid function during pregnancy

OBJECTIVE

The aim of this study was to establish the risk of postpartum thyroid dysfunction (PPTD) in women who had normal thyroid function during pregnancy and no history of thyroid disease.

DESIGN

Four thousand and twenty-two consecutive pregnant women were screened for thyroid function and antithyroid antibody. Among women with normal thyroid function during pregnancy and no history of thyroid disease, thyroid function were assessed in 131 of 388 antithyroid antibody positive (Group I) and 1030 of 3503 antibody negative (Group II) women at 1 and 3 months postpartum. In Group I women who experienced PPTD, the frequency of later manifestation of Hashimoto's disease was compared according to titres of antithyroid antibodies.

MEASUREMENTS

Blood samples in early pregnancy, and at 1 month and 3 months postpartum were obtained using the dried blood spot method. Levels of fT4 were measured by RIA, TSH by fluoroimmunoassay or ELISA, antimicrosome antibody (AMC) and antithyroglobulin antibody (ATG) by indirect agglutination reactions.

RESULTS

The prevalence of PPTD at 1 month and 3 months postpartum were found to be 6.9% and 21.3% in Group I, and 5.3% and 4.7% in Group II, respectively. The prevalence of PPTD was significantly higher at 3 months postpartum in Group I (P<0.05). 27.3% of women with PPTD in Group I were later found to have Hashimoto's disease and 9.1% manifested hypothyroidism without goitre. A high AMC titre (> or = 25600) at 3 months postpartum in women with PPTD was related to the manifestation of Hashimoto's disease. AMC titres of PPTD women and women who developed Hashimoto's disease were significantly higher than those of control women who did not experience PPTD.

CONCLUSION

A high prevalence of PPTD was found in women with antithyroid antibodies who were euthyroid during pregnancy. Prolonged follow-up of the subsequent thyroid function may be needed in women who experience PPTD and/or show a high titre of antithyroid antibody.

Thyroid disease in relation to pregnancy: a decade of change

Inspection of the references cited in this review indicates that much work has occurred in the area of thyroid and pregnancy during the last decade. Significant advances in our understanding of the immunology of pregnancy and the effect of thyroid disease on this process have taken place. The role of hCG in the physiology of pregnancy and its relevance to thyroid function has been an emerging theme. There is still no clear explanation for the association between thyroid antibodies and infertility or miscarriage. During the last decade a general concensus has developed in relation to the management of hyperthyroidism in pregnancy although there are still variations in antithyroid drug use at this time. The aetiological classification of congenital hyper- and hypothyroidism utilizing new technologies has opened up a new perspective on these disorders. Attention has been drawn to the importance of treating maternal hypothyroidism with adequate thyroid replacement therapy and to the possibility of impaired child neuropsychological development consequent on low maternal thyroid hormone concentration in early gestation in non iodine deficient areas. Significant advances have been made during the last decade in the description of the clinical features and in our understanding of the pathogenesis of postpartum thyroid disease. The importance of long-term follow up of selected patient groups has also been emphasized.

Prevalence and characteristics of postpartum thyroid dysfunction in São Paulo, Brazil

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.

Recognizing, understanding, and treating postpartum thyroiditis

Postpartum thyroiditis is the most common endocrinologic disorder, with an incidence that varies geographically from 5% to 10%. It has important clinical sequelae including symptoms of hyperthyroidism, hypothyroidism, and depression. Long-term follow-up of women who experience postpartum thyroiditis reveals a high recurrence rate in subsequent pregnancies. Postpartum thyroiditis is an autoimmune disorder, and thyroid antibody-positive women in the first trimester have a 33% to 50% chance of developing thyroiditis in the postpartum period. Whether or not to screen for postpartum thyroiditis remains controversial.

The value of ultrasonography in predicting autoimmune thyroid disease

Ultrasonography (US) may demonstrate a diffuse reduction in thyroid echogenicity (low-amplitude echoes) in autoimmune thyroid disease (AITD), which includes chronic lymphocytic thyroiditis and Graves' disease, as well as in subacute thyroiditis. The reported occurrence of this finding in AITD varies from 19% to 95%. To assess the validity of diffuse reduction in thyroid echogenicity as a predictor of AITD, 3,077 patients referred for US of the thyroid were examined prospectively with regard to reduced versus normal thyroid echogenicity. The most frequent reasons for referral were goiter, thyroid dysfunction, neck discomfort, and/or difficulty in swallowing. Ultrasonography demonstrated diffuse reduction in thyroid echogenicity in 485 patients. Of these, 452 patients had available records of fine-needle aspiration biopsy (FNAB), and were included in the study. From the remaining patients, with normal thyroid echogenicity, 100 consecutive patients were selected as controls. In 411 of the 452 study patients (90.9%) there was at least one laboratory finding consistent with possible AITD: cytology indicating lymphocytic thyroiditis, 287 of 363 patients (79.1%) with diagnostic specimens; elevated levels of peroxidase antibodies (TPOAb), 225 of 337 (66.8%); elevated thyrotropin (TSH) levels, 290 of 450 (64.4%); or low TSH levels, 79 of 450 (17.6%). The final diagnosis was: chronic autoimmune (Hashimoto's) thyroiditis in 352 patients; Graves' disease in 47 patients; subacute (granulomatous) thyroiditis in 7 patients; toxic nodular goiter in 3 patients; and toxic adenoma in 2 patients. In the remaining 41 patients, those without laboratory results consistent with AITD, the final diagnosis was colloid goiter in 37 and thyroid cancer in 4 patients. In the 100 controls, laboratory results were consistent with possible AITD in 14 patients: elevated TPOAb levels in 5 of 49 patients with retrieved antibody results; lymphocytic thyroiditis in 2 patients; elevated TSH levels in 2 patients; and low TSH levels in 2 patients. In these controls, the final diagnosis was: chronic autoimmune thyroiditis in 7; toxic nodular goiter in 6 patients, and toxic adenoma in 1 patient. The corresponding positive and negative predictive values of reduced thyroid echogenicity as an indicator of AITD were 399 of 452 (88.3% [95% CI, 85% to 91%]), and 93 of 100 (93.0% [95% CI, 88% to 98%]), respectively. Thus, diffuse reduction in thyroid echogenicity was a valid predictor of AITD.

Transient diffuse low thyroid echogenicity in painless postpartum thyroiditis: report of two cases

We report two cases of chronic autoimmune thyroiditis, one patient with recurrent painless thyroiditis and another with recurrent postpartum thyroiditis. In these two patients, the episode of subacute thyroiditis seemed to be immune mediated. Thyroid ultrasonography showed a diffuse, markedly hypoechogenic gland, coinciding with each of the episodes of transient thyroid dysfunction that reverted to a normal echographic appearance with recovery of normal thyroid function. These two cases show that a diffuse low echogenicity of the thyroid, frequently seen in autoimmune thyroid disorders, can be a reversible event and suggest that the transient nature of certain forms of hypothyroidism may be predicted by a follow-up echographic examination. Further studies with a larger number of patients are required to confirm this observation.

Clinical manifestations of postpartum thyroid disease

Postpartum thyroiditis (PPT) occurs in 5%-9% of unselected postpartum women; hyperthyroidism and hypothyroidism develop, the latter being permanent, in up to 25 %-30% of women. PPT is strongly associated with antithyroid peroxidase (anti-TPO) antibodies, but 50% of anti-TPO positive women do not develop thyroid dysfunction. Symptom analysis has shown that lack of energy and irritability were the most frequent hyperthyroid symptoms whereas lack of energy, aches and pains, poor memory, dry skin, and cold intolerance were the significant hypothyroid features. Some of these symptoms were more frequently observed than in antibody-negative controls even when these patients were euthyroid and in anti-TPOAb positive women who did not develop PPT at all. The diagnosis of PPT is based on the observation of abnormal thyroid function tests in a postpartum anti-TPOAb-positive woman: transient hyperthyroidism occurs at 14 weeks and hypothyroidism at 19 weeks postpartum. Diffuse or multifocal hypoechogenicity of the thyroid is seen on echography and a thyroid destructive process is evidenced by an increase in serum thyroglobulin and urinary iodine excretion. In addition to the 25%-30% of women who develop permanent hypothyroidism at 3 years, recent data indicate that 50% of women who have developed PPT will be hypothyroid 7-9 years later. The long-term risk is only 5% for those anti-TPOAb positive women not developing thyroid dysfunction postpartum. The risk of recurrent PPT is 70% if previous PPT was experienced and 25% if the patient was euthyroid after the first pregnancy.

The value of thyroid parenchymal echogenicity as an indicator of pathology using the sternomastoid muscle for comparison

This study was undertaken to evaluate the diagnostic accuracy of comparison of the echogenicity of the thyroid gland with the sternomastoid muscle in diagnosis of thyroid disorders. Fifty healthy subjects underwent a thyroid ultrasound, and 80 patients with archived thyroid ultrasound examinations (50 thyrotoxicosis and 30 thyroiditis) were reviewed. Images were measured for the image density of the thyroid gland and the sternomastoid muscle, using a transmission densitometer. Healthy thyroid was relatively hyperechoic when compared with the sternomastoid muscle (100%). Of the thyrotoxic patients, 70% showed a relatively hyperechoic thyroid compared to 47% of the thyroiditis patients. Mean image density difference in healthy thyroid, thyrotoxicosis and thyroiditis ranged from 0.1 to 1, -0.42 to 0.83, and -0.55 to 0.58, respectively. In conclusion, the relative echogenicity of the thyroid gland when compared with the sternomastoid muscle may be useful to differentiate healthy thyroid from thyrotoxicosis and thyroiditis, but does not help to distinguish thyrotoxicosis from thyroiditis. An image density difference of less than 0.1 may be considered to be abnormal, whereas a value greater than 0.83 may be considered to be normal.

Imaging the thyroid

Thyroid imaging has historically relied heavily on scintigraphy, although, not surprisingly in view of the superficial position of the gland, ultrasound has assumed an increasingly prominent role in recent years. The other cross-sectional imaging modalities can also be useful, and the emergence of new radiopharmaceuticals and the increasingly central role of fine needle aspiration cytology have further added to the range of diagnostic techniques available. This review attempts to summarize the current state of knowledge, and makes some suggestions for the most efficient use of imaging resources in the investigation of thyroid disease.

Serum thyroglobulin: an early indicator of autoimmune post-partum thyroiditis

OBJECTIVE

The aim of this study was to assess whether autoimmune thyroid damage in post-partum thyroiditis was accompanied by a significant rise in the concentration of thyroglobulin in the serum and whether its measurement could be useful in the prediction of the risk and severity of an episode of post-partum thyroid dysfunction.

PATIENTS

Fifty-one women, who had taken part in a larger survey of post-partum thyroiditis, were selected at random for this study. Fourteen women without elevated circulating thyroid autoantibodies and 21 with raised thyroid autoantibodies remained euthyroid throughout the post-partum year. A third group of 14 women had raised thyroid autoantibody levels and showed one or more episodes of thyroid dysfunction during the course of the first year post partum.

MEASUREMENTS

Thyroid autoantibodies were measured by ELISA, free T3 and free T4 by the Amerlex M method and TSH by an immunoradiometric method. Serum thyroglobulin was measured by a method free from interference by circulating endogenous thyroglobulin autoantibodies. Thyroid ultrasonography was performed using a General Electric RT3600 scanner operating at 7.5 MHz.

RESULTS

Fourteen control women had a mean serum thyroglobulin concentration of 3.3 micrograms/l (SD 4.4; range < 1-12 micrograms/l; 95% confidence interval up to 6.0 micrograms/l). Twenty-one thyroid autoantibody positive euthyroid women had a mean serum thyroglobulin level of 5.8 micrograms/l (SD 6.2; range < 1-36 micrograms/l) which was not significantly different from that seen in the control group. Sixteen thyroid autoantibody positive women who showed one or more episodes of thyroid dysfunction during the post-partum period had a mean serum thyroglobulin of 31 micrograms/l (SD 24.8; range up to 88 micrograms/l) and this was significantly elevated compared with both the control and antibody positive groups (P < 0.001). Serum thyroglobulin concentrations at 3 months post partum correlated with the degree of post-partum hypothyroidism (as indicated by the maximum TSH and the minimum free thyroxine concentrations post partum) and, in those cases where thyroid ultrasound examinations were performed, with the degree of lymphocytic infiltration of the thyroid gland.

CONCLUSIONS

The data presented in this paper confirm the destructive nature of post-partum thyroiditis and indicate that the measurement of serum thyroglobulin concentration could assist in the identification of those women at risk of post-partum thyroiditis.

The iodide perchlorate discharge test in women with previous post-partum thyroiditis: relationship to sonographic appearance and thyroid function

BACKGROUND

Post-partum thyroid disease occurs in 50% of anti-thyroid peroxidase (TPO) antibody positive women (detected at 16 weeks' gestation) and is characterized by a transient episode of hyper, hypo or hyper-hypothyroidism. In approximately 20% of these women the hypothyroidism is permanent. However, the extent of long-term thyroid dysfunction, possibly mediated by immune attack, in those anti-TPO Ab + ve women who have had only transient or no thyroid dysfunction during the postpartum period is not clear.

OBJECTIVE

We have therefore studied the frequency of iodide organification defects by iodide perchlorate discharge testing, and of thyroid morphological abnormalities by ultrasound scanning in euthyroid women following their episode of post-partum thyroiditis (PPT).

DESIGN

The study group comprised 17 women with previous PPT (PPT + ve) and 12 women who had positive anti-TPO antibodies during pregnancy but who did not develop PPT (PPT - ve). Women were studied 15-47 months following their episode of PPT.

RESULTS

Iodide perchlorate discharge tests were positive (more than 10% discharge) in 7 (41%) PPT + ve and 5 (42%) PPT-ve subjects (P = NS). Morphological abnormalities on thyroid ultrasound were detected in 7 of 14 (50%) PPT + ve and 7 of 9 (77%) PPT - ve subjects (P = NS). There was a strong association between abnormalities of iodide organification and morphology: of 11 subjects with positive iodide perchlorate discharge tests, 10 had abnormal (positive) ultrasound scans; of 12 subjects with negative iodide perchlorate discharge tests 8 had negative ultrasound scans (P = 0.013, Fisher's exact test).

CONCLUSIONS

Long-term subtle defects of thyroid function and morphology are common in women with anti-TPO antibodies in pregnancy, whether or not they develop post-partum thyroiditis. The clinical significance of these findings is unclear but a continuing thyroid pathological process is suggested.