The research on hypothyroidism during pregnancy has been a hot field concerned by endocrinologists. This editorial highlights six aspects of consensus reached by American Endocrine Association in "Management of Thyroid Dysfunction during Pregnancy and Postpartum: An Endocrine Society Clinical Practice Guideline" in 2007. The appropriate diagnosis of thyroid dysfunction depends on gestational specific reference intervals of thyroid hormones, and otherwise the pregnant women with subclinical hypothyroidism will suffer from missed diagnosis. There are three types of subclinical thyroid disorders during pregnancy, namely subclinical hypothyroidism, hypothyroxinemia and simple positive thyroid peroxidase autoantibodies. The opinions on thediagnosis of these disorders are proposed in the context.

“The guideline for the diagnosis and management of thyroid diseases during pregnancy and postpartum in China” written by Chinese Society of Endocrinology and Chinese Society of Perinatal Medicine is now formally published.This guideline was written following the principles of “based on the national conditions,evidencebased medicine,being innovative and realistic,and resource sharing”.It is modeled on the guideline issued by American Thyroid Association in 2011,joining the research of domestic scholars and combining with the actual situation of domestic clinical work and maternal and child health.This guideline contains 11 chapters,taking question terms and recommendation terms in the model,and a total of 68 problem terms and 57 recommendation terms.This paper deeply discusses the problems about the diagnosis and treatment of subclinical hypothyroidism during pregnancy,as well as the importance of establishing gestation-specific TSH reference interval.

Guidelines on the Diagnosis and Treatment of Thyroid Nodules and Differentiated Thyroid Carcinomas is written by Chinese Society of Endocrinology,Chinese Society of General Surgery Endocrinology Group,China Anti-Cancer Association Head and Neck Tumor Professional Committee,and Chinese Society of Nuclear Medicine.The guideline has systematically established a series of standards related to thyroid nodules.It reflects the scientific spirit of multidisciplinary cooperation and mutual understanding.

For the first time,the iodine-induced thyroid diseases group of China Medical University has finished a five-year prospective epidemiological study on the incidences of thyroid diseases in the three communities with various levels of iodine intake.The results indicated that increased incidences of subclinical hypothyroidism and autoimmune thyroiditis in the communities with more than adequate and excessive iodine intake.The individuals with positive thyroid autoantibodies at baseline more likely became hypothyroid due to more than adequate and excessive iodine intake.These adverse effects are mainly involved in the susceptible populations for thyroid diseases.Hence it appears to be reasonable that iodine supplementation should be conducted by localization and individualization.

hypothyroidism is a common subclinical disease in endocrinology. Its diagnosis is based on an elevated serum TSH but normal FT 4 levels. The adverse outcome of subclinical hypothyroidism is progressing to overt hypothyroidism with an increased risk for atherosclerosis and myocardial infarction . Two factors may affect the development of overt hypothyroidism: the levels of serum TSH and thyroid autoantibodies and both factors have additional effects on the outcome. The benefits of treatment with T 4for preventing the development of overt hypothyroidism is not yet certain; subclinical hypothyroidism is a strong indicator of risk for atherosclerosis and myocardial infarction, just like other known major risk fators such as hypercholestrolemia, hypertension, smoking and diabetes (odds ratio for aortic atherosclerosis 1.9; odds ratio for myocardial infarction 3.1). The treatment with T 4 for the patients could reduce the levels of serum cholesterol. The effects of subclinical hypothyroidism in pregnant women on the IQ of their children have been widely focused. According to the results from a published epidemiological study, the normal reference values of TSH, thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TgAb) detected by immunochemiluminesence assay (ICMA) method and the cut-off values of TPOAb and TgAb associated with thyroid diseases have been proposed.

Recently, more and more attention have been paid to the impact of maternal thyroid hormones on neuropsychologic development of offspring. In the first 20 weeks of gestation, neuropsychologic development of the fetus is mostly dependent on thyroxine from the mother. Limited epidemiological data showed that full-scale WISC IQs averaged 7 points lower among children born to mothers with undiagnosed thyroid deficiency during pregnancy, in comparison with control children. The main cause of subclinical maternal hypothyroidism is autoimmune thyroiditis. Data from basic studies have confirmed the impacts of maternal thyroid hormones on the neurodevelopmental outcomes of offspring. In a Chinese female population, the positive rate of thyroid autoantibodies was 11.0%, and the prevalence of postpartum thyroiditis was 11.9%. Hence, it is necessary to set up a screening schedule for subclinical hypothyroidism and autoimmne thyroiditis in pregnant women, which is of great value for the health of both women and children.

Guidelines of the American Thyroid Association (ATA) proposed two diagnostic criteria for subclinical hypothyroidism during the first trimester of pregnancy:criterion 1 was based on the pregnancy-specific TSH reference range and criterion 2 on serum TSH＞2.5 mIU/L level with normal serum FT4.According to the results of the Subclinical hypothyroidism during early pregnancy study,author proposed that criterion 2 is not appropriate for Chinese pregnant women because the TSH concentration has become significantly higher in whole Chinese population.By using criterion 2,the prevalence may be as high as 27.8％,which may result in over-diagnosis and over treatment.

[Summary] The incidence of thyroid cancer in China is increasing rapidly, at an annual percentage change (APC)of 20. 1%, while the APC of mortality of thyroid cancer is only 1. 6%, which is defined asoverdiagnosis by the experts of tumor field. This tendency is due to the over-screening for thyroid nodules and cancers with high resolution of B ultrasound equipments. The prevalence of latent thyroid cancer is 11. 5% in human-being as found by the autopsy. However, the prognosis of the majority of patients is good. The clinical doctors and health-care department of government in China should take actions to deal with the tendency of over-screening andoverdiagnosisfor thyroid nodules and cancers.

Thyroid hormones play important roles in growth, development, and metabolism of various cells and tissues. It has been assumed for a long time that thyroid hormones are lipophilic and enter cells by passive diffusion, but it has become increasingly clear that cellular uptake and efflux of thyroid hormones are mediated by transporters. The discovery of these thyroid hormone transporters will lead to a better understanding of the tissuespecific regulation of thyroid hormones.

Maternal hypothyroidism can cause adverse outcomes for both the pregnancy and fetus, and may affect intelligence quotient of the offspring. This article reviews mainly the diagnosis and treatment of maternal hypothyroidism.