Pregnancy and thyroid diseases in China

2017 Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and the Postpartum

BACKGROUND

Thyroid disease in pregnancy is a common clinical problem. Since the guidelines for the management of these disorders by the American Thyroid Association (ATA) were first published in 2011, significant clinical and scientific advances have occurred in the field. The aim of these guidelines is to inform clinicians, patients, researchers, and health policy makers on published evidence relating to the diagnosis and management of thyroid disease in women during pregnancy, preconception, and the postpartum period.

METHODS

The specific clinical questions addressed in these guidelines were based on prior versions of the guidelines, stakeholder input, and input of task force members. Task force panel members were educated on knowledge synthesis methods, including electronic database searching, review and selection of relevant citations, and critical appraisal of selected studies. Published English language articles were eligible for inclusion. The American College of Physicians Guideline Grading System was used for critical appraisal of evidence and grading strength of recommendations. The guideline task force had complete editorial independence from the ATA. Competing interests of guideline task force members were regularly updated, managed, and communicated to the ATA and task force members.

RESULTS

The revised guidelines for the management of thyroid disease in pregnancy include recommendations regarding the interpretation of thyroid function tests in pregnancy, iodine nutrition, thyroid autoantibodies and pregnancy complications, thyroid considerations in infertile women, hypothyroidism in pregnancy, thyrotoxicosis in pregnancy, thyroid nodules and cancer in pregnant women, fetal and neonatal considerations, thyroid disease and lactation, screening for thyroid dysfunction in pregnancy, and directions for future research.

CONCLUSIONS

We have developed evidence-based recommendations to inform clinical decision-making in the management of thyroid disease in pregnant and postpartum women. While all care must be individualized, such recommendations provide, in our opinion, optimal care paradigms for patients with these disorders.

Thyroid function testing in women who had a stillbirth

CONTEXT

Thyroid dysfunction is thought to be associated with stillbirth. Therefore, thyroid function is often recommended in the diagnostic investigations for stillbirth.

OBJECTIVE

We aimed to evaluate the added value of thyroid function testing in the diagnostic investigations for stillbirth.

DESIGN AND PATIENTS

A nationwide multicentre prospective cohort study in 1025 women who suffered stillbirth >20 weeks of gestation performed between 2002 and 2008. In each woman, an extensive diagnostic work-up was performed, including placental examination and autopsy. TSH and FT4 values below the 2·5th percentile or above the 97·5th percentile according local laboratory reference values were regarded as abnormal. Women with a history of thyroid disease were evaluated separately.

MAIN OUTCOME MEASURES

Thyroid function abnormalities in women with stillbirth.

RESULTS

Of 1025 included women, 21 had a history of thyroid disease (2%). In the 875 with TSH and FT4 results and no history of thyroid disease, 10% had hypothyroxinemia, 4·6% subclinical hypothyroidism, 1·6% overt hypothyroidism and 1·5% subclinical hyperthyroidism. Women with a subclinical hyperthyroidism more often had a foetal death caused by foetal hydrops: 23% vs 2·9% (adjusted OR 10·3, 95% CI 2·5-42).

CONCLUSIONS

Women with a stillbirth had a slightly higher prevalence of overt hypothyroidism, subclinical hypothyroidism and hypothyroxinaemia compared to previous studies on thyroid dysfunction in pregnant women. Given the absence of a strong associations with the cause of stillbirth, and no demonstrated beneficial effects of treating thyroid dysfunction in these women, routine screening after stillbirth is not justified.

Thyroid screening in pregnancy

The adverse impact of overt hypothyroidism that complicates pregnancy outcomes is well-established and not debated. For more than a decade, however, endocrinologists and obstetricians have been debating whether screening for subclinical thyroid disorders during pregnancy should be routine or should continue to be based on symptoms and risk factors. Several observational studies have suggested that offspring of women with asymptomatic thyroid dysfunction were at increased risk for impaired neurodevelopment. Other studies have suggested that pregnant women with subclinical thyroid disease, particularly those identified with an elevated thyroid-stimulating hormone (TSH) level may be at increased risk for pregnancy complications such as fetal death, preterm birth, or placental abruption. These data have prompted both obstetric and endocrinologic professional societies to draft recommendations regarding screening for thyroid disease during pregnancy, some of which are not entirely based on available evidence. The prevalence of overt thyroid disease is estimated to be 1-2 per 1000 pregnancies and historically has not been considered high enough to justify routine screening. Lower TSH thresholds (>2.5 mU/L) for the diagnosis of hypothyroidism have been promoted, and women with subclinical thyroid dysfunction commonly are included in estimates of thyroid disease during pregnancy, both of which exaggerate prevalence rates. The most compelling recent evidence on this issue has come from the Controlled Antenatal Thyroid Screening trial. After almost 22,000 pregnant women were screened for either isolated high TSH or isolated low free thyroxine level, 390 children of treated women with either diagnosis were compared with 404 children of similar women who were not treated during pregnancy. Treatment had no effect on mean offspring IQ at age 3 years or the number of children with an IQ <85. Authors of this landmark study concluded that antenatal screening and maternal treatment for women with subclinical thyroid dysfunction did not result in improved cognitive function. An ongoing intervention trial conducted by the Eunice Kennedy-Shriver National Institute of Child Health and Human Development's Maternal-Fetal Medicine Units Network will provide further clarity to this important question. In the interim, the debating authors have concluded, after careful review of the currently published literature, that routine screening for subclinical thyroid dysfunction during pregnancy is not currently warranted at this time.

Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association

OBJECTIVE

Hypothyroidism has multiple etiologies and manifestations. Appropriate treatment requires an accurate diagnosis and is influenced by coexisting medical conditions. This paper describes evidence-based clinical guidelines for the clinical management of hypothyroidism in ambulatory patients.

METHODS

The development of these guidelines was commissioned by the American Association of Clinical Endocrinologists (AACE) in association with American Thyroid Association (ATA). AACE and the ATA assembled a task force of expert clinicians who authored this article. The authors examined relevant literature and took an evidence-based medicine approach that incorporated their knowledge and experience to develop a series of specific recommendations and the rationale for these recommendations. The strength of the recommendations and the quality of evidence supporting each was rated according to the approach outlined in the American Association of Clinical Endocrinologists Protocol for Standardized Production of Clinical Guidelines-2010 update.

RESULTS

Topics addressed include the etiology, epidemiology, clinical and laboratory evaluation, management, and consequences of hypothyroidism. Screening, treatment of subclinical hypothyroidism, pregnancy, and areas for future research are also covered.

CONCLUSIONS

Fifty-two evidence-based recommendations and subrecommendations were developed to aid in the care of patients with hypothyroidism and to share what the authors believe is current, rational, and optimal medical practice for the diagnosis and care of hypothyroidism. A serum thyrotropin is the single best screening test for primary thyroid dysfunction for the vast majority of outpatient clinical situations. The standard treatment is replacement with L-thyroxine. The decision to treat subclinical hypothyroidism when the serum thyrotropin is less than 10 mIU/L should be tailored to the individual patient.

Subclinical thyroid disease

INTRODUCTION

Subclinical thyroid disease is a common finding on testing of thyroid function and its management remains controversial.

SOURCE OF DATA

Epidemiological data from large population studies from USA and Europe.

AREAS OF AGREEMENT

There is an increased risk of progression to overt hypothyroidism or hyperthyroidism. The treatment of mild thyroid failure is of importance in optimizing pregnancy outcome.

AREAS OF CONTROVERSY

Diagnostic criteria differ and there is variation between management guidelines. The difference was found in long-term clinical outcomes between endogenous and exogenous subclinical hyperthyroidism.

GROWING POINTS

Meta-analyses have provided epidemiological data in cardiovascular mortality and morbidity in subclinical thyroid disease. Increased use of echocardiography and bone markers in identifying those who benefit from intervention.

AREAS TIMELY FOR DEVELOPING RESEARCH

A randomized controlled trial to identify those subjects identified from screening programmes that benefit from intervention in terms of morbidity and mortality.

Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association

BACKGROUND

Hypothyroidism has multiple etiologies and manifestations. Appropriate treatment requires an accurate diagnosis and is influenced by coexisting medical conditions. This paper describes evidence-based clinical guidelines for the clinical management of hypothyroidism in ambulatory patients.

METHODS

The development of these guidelines was commissioned by the American Association of Clinical Endocrinologists (AACE) in association with American Thyroid Association (ATA). AACE and the ATA assembled a task force of expert clinicians who authored this article. The authors examined relevant literature and took an evidence-based medicine approach that incorporated their knowledge and experience to develop a series of specific recommendations and the rationale for these recommendations. The strength of the recommendations and the quality of evidence supporting each was rated according to the approach outlined in the American Association of Clinical Endocrinologists Protocol for Standardized Production of Clinical Guidelines-2010 update.

RESULTS

Topics addressed include the etiology, epidemiology, clinical and laboratory evaluation, management, and consequences of hypothyroidism. Screening, treatment of subclinical hypothyroidism, pregnancy, and areas for future research are also covered.

CONCLUSIONS

Fifty-two evidence-based recommendations and subrecommendations were developed to aid in the care of patients with hypothyroidism and to share what the authors believe is current, rational, and optimal medical practice for the diagnosis and care of hypothyroidism. A serum thyrotropin is the single best screening test for primary thyroid dysfunction for the vast majority of outpatient clinical situations. The standard treatment is replacement with L-thyroxine. The decision to treat subclinical hypothyroidism when the serum thyrotropin is less than 10 mIU/L should be tailored to the individual patient.

Variable iodine intake persists in the context of universal salt iodization in China

Iodine deficiency disorders were prevalent in China until the introduction of universal salt iodization in 1995. Concerns have recently arisen about possible excess iodine intake in this context. To document iodine intake and the contribution from iodized salt in China, we surveyed dietary iodine intake during China's nationally representative 2007 total diet study (TDS) and during an additional TDS in 4 coastal provinces and Beijing in 2009. Iodine intake was broken down by age and sex in 2009. Mean daily iodine and salt intake and the contribution from different food and beverage groups (and in 2009, individual items) was measured. The iodine in food cooked with iodized and noniodized salt was also assessed. The mean calculated iodine intake of a standard male in China was 425 μg/d in 2007 and 325 μg/d in coastal areas in 2009, well below the upper limit (UL) in all provinces. In 2009, iodine intake was above the UL in only 1-7% of age-sex groups, except among children (18-19%). A concerning number of individuals consumed less than the WHO-recommended daily allowance, including 31.5% of adult women. Salt contributed 63.5% of food iodine, and 24.6% of salt iodine was lost in cooking. Overall salt consumption declined between the surveys. Salt iodization assures iodine nutrition in China where environmental iodine is widely lacking. The risk of iodine excess is low, but planned decreases in salt iodization levels may increase the existing risk of inadequate intake. Regular monitoring of urinary iodine and more research on the impact of excess iodine intake is recommended.