Thyroid disease in pregnant women with systemic lupus erythematosus: increased preterm delivery

Thyroid disease is common in pregnancy and is associated with miscarriage, preterm delivery and postpartum thyroiditis (PPT). Systemic lupus erythematosus (SLE) is associated with miscarriage and preterm delivery. The hypotheses of the study are (1) pregnant women with SLE will have a high prevalence of undiagnosed hypothyroidism and a high prevalence of PPT, and (2) women with SLE and thyroid disease will have an increased incidence of adverse pregnancy outcomes as compared with pregnant women with SLE who do not have thyroid disease. This was a retrospective study of the Hopkins Lupus Cohort. All women had thyroid-stimulating hormone and thyroid antibodies assayed on frozen sera. In total, 63 pregnant women who met the ACR classification for SLE were evaluated. Outcome measures were the prevalence of thyroid disease during pregnancy and postpartum, and pregnancy outcomes. Some 13% of the women were on thyroid hormone prior to becoming pregnant, 11% were diagnosed with hypothyroidism during pregnancy, and 14% developed PPT. The prevalence of preterm delivery was 67% in women with thyroid disease and 18% in women who were thyroid disease free (p?=?0.002). The presence of thyroid antibodies was not correlated with preterm delivery. Pregnant women with SLE have an increased prevalence of thyroid disease. Women with SLE and thyroid disease have an increased prevalence of preterm delivery.     

Subclinical hypothyroidism is an independent risk factor for atherosclerosis and myocardial infarction in elderly women: the Rotterdam Study

BACKGROUND: Overt hypothyroidism has been found to be associated with cardiovascular disease. Whether subclinical hypothyroidism and thyroid autoimmunity are also risk factors for cardiovascular disease is controversial. OBJECTIVE: To investigate whether subclinical hypothyroidism and thyroid autoimmunity are associated with aortic atherosclerosis and myocardial infarction in postmenopausal women. DESIGN: Population-based cross-sectional study. SETTING: A district of Rotterdam, The Netherlands. PARTICIPANTS: Random sample of 1149 women (mean age +/- SD, 69.0 +/- 7.5 years) participating in the Rotterdam Study. MEASUREMENTS: Data on thyroid status, aortic atherosclerosis, and history of myocardial infarction were obtained at baseline. Subclinical hypothyroidism was defined as an elevated thyroid-stimulating hormone level (>4.0 mU/L) and a normal serum free thyroxine level (11 to 25 pmol/L [0.9 to 1.9 ng/dL]). In tests for antibodies to thyroid peroxidase, a serum level greater than 10 IU/mL was considered a positive result. RESULTS: Subclinical hypothyroidism was present in 10.8% of participants and was associated with a greater age-adjusted prevalence of aortic atherosclerosis (odds ratio, 1.7 [95% CI, 1.1 to 2.6]) and myocardial infarction (odds ratio, 2.3 [CI, 1.3 to 4.0]). Additional adjustment for body mass index, total and high-density lipoprotein cholesterol level, blood pressure, and smoking status, as well as exclusion of women who took beta-blockers, did not affect these estimates. Associations were slightly stronger in women who had subclinical hypothyroidism and antibodies to thyroid peroxidase (odds ratio for aortic atherosclerosis, 1.9 [CI, 1.1 to 3.6]; odds ratio for myocardial infarction, 3.1 [CI, 1.5 to 6.3]). No association was found between thyroid autoimmunity itself and cardiovascular disease. The population attributable risk percentage for subclinical hypothyroidism associated with myocardial infarction was within the range of that for known major risk factors for cardiovascular disease. CONCLUSION: Subclinical hypothyroidism is a strong indicator of risk for atherosclerosis and myocardial infarction in elderly women.     

The role of thyroid autoimmunity in fertility and pregnancy

The thyroid gland and gonadal axes interact continuously before and during pregnancy. Hypothyroidism influences ovarian function by decreasing levels of sex-hormone-binding globulin and increasing the secretion of prolactin. In women of reproductive age, hypothyroidism can be reversed by thyroxine therapy to improve fertility and avoid the need for use of assisted reproduction technologies. For infertile women, preparation for medically assisted pregnancy comprises controlled ovarian hyperstimulation that substantially increase circulating estrogen concentrations, which in turn can severely impair thyroid function. In women without thyroid autoimmunity these changes are transient, but in those with thyroid autoimmunity estrogen stimulation might lead to abnormal thyroid function throughout the remaining pregnancy period. Prevalence of thyroid autoimmunity is significantly higher among infertile women than among fertile women, especially among those whose infertility is caused by endometriosis or ovarian dysfunction. Presence of thyroid autoimmunity does not interfere with normal embryo implantation, but the risk of early miscarriage is substantially raised. Subclinical and overt forms of hypothyroidism are associated with increased risk of pregnancy-related morbidity, for which thyroxine therapy can be beneficial. Systematic screening for thyroid disorders in pregnant women remains controversial but might be advantageous in women at high risk, particularly infertile women.     

Thyroid autoimmunity and aging

Aging is associated with the appearance of several serum autoantibodies, including thyroid autoantibodies. The biological and clinical significance of this phenomenon is still unknown, because, with the exception of primary myxedema, the prevalence of clinically overt thyroid autoimmune diseases is not increased in the elderly. The peculiar link between autoimmune thyroid failure and aging is also underscored by the high prevalence of subclinical hypothyroidism in elderly subjects with positive serum thyroid autoantibodies, and could be the consequence of preferential age-dependent expression of destructive effector mechanisms and/or increased target gland susceptibility. Thyroid autoimmunity and subclinical hypothyroidism have been also implicated in the pathogenesis of other age-associated disorders, in particular coronary heart disease. Interestingly, recent data from our laboratories showed that thyroid autoantibodies are rare in healthy centenarians and in other highly selected aged populations, while they are frequently observed in unselected or hospitalized elderly. Taken together, these data suggest that thyroid autoimmune phenomena are not the consequence of the aging process itself, but rather might be related to age-associated disease.     

亚临床甲状腺功能减退症

亚临床甲状腺功能减退症(甲减)是一种业临床甲状腺疾病.诊断标准是血清促甲状腺激素(TSH)水平高于正常上限而游离T4水平尚在正常范围.目前全世界业临床甲减的平均患病率为4%～10%,主要发生在女性和老年人群.桥本甲状腺炎是最常见的病因.其卡要的临床危害包括引起血脂异常、导致动脉粥样硬化和,冠心病、影响认知功能,还可导致不孕和流产.治疗主要针对血清TSH10 mIU/L的患者,应用左旋-T4替代治疗.对于血清TSH 4～10 mIU/L,特别是甲状腺自身抗体阳性者需密切监测.此外,对妊娠期亚临床甲减患者的治疗要求控制TSH<2.5 mlU/L.     

亚临床甲状腺功能减退症

亚临床甲状腺功能减退症（甲减）是一种亚临床甲状腺疾病。诊断标准是血清促甲状腺激素（TSH）水平高于正常上限而游离T4水平尚在正常范围。目前全世界亚临床甲减的平均患病率为4％-10％,主要发生在女性和老年人群。桥本甲状腺炎是最常见的病因。其主要的临床危害包括引起血脂异常、导致动脉粥样硬化和冠心病、影响认知功能,还可导致不孕和流产。治疗主要针对血清TSH〉10ml U／L的患者,应用左旋-T4替代治疗。对于血清TSH4～10ml U／L,特别是甲状腺自身抗体阳性者需密切监测。此外,对妊娠期亚临床甲减患者的治疗要求控制TSH〈2．5ml U／L。     

Long-term follow-up of 106 multiple sclerosis patients undergoing interferon-beta 1a or 1b therapy: predictive factors of thyroid disease development and duration

BACKGROUND: Conflicting data have been reported on the association between interferon (IFN)-beta therapy of multiple sclerosis (MS) patients and thyroid disease development. AIMS: The goals of this study are as follows: to assess the actual occurrence of thyroid dysfunction and autoimmunity during long-term IFN-beta therapy; to establish the possible presence of predictive factors for thyroid dysfunction development and duration; and to suggest an effective follow-up protocol for patients receiving long-term IFN-beta therapy. STUDY PROTOCOL: A total of 106 MS patients (76 women) underwent IFN-beta 1a or 1b therapy for up to 84 months (median, 42 months). Thyroid function and autoimmunity were assessed at baseline and every 3-6 months throughout the treatment course. RESULTS: Baseline thyroid autoimmunity was detected in 8.5% of patients and hypothyroidism in 2.8%. Thyroid dysfunction (80% hypothyroidism, 92% subclinical, 56% transient) developed in 24% (68% with autoimmunity) of patients and autoimmunity in 22.7% (45.5% with dysfunction), without significant differences between the two cytokines; 68% of dysfunctions occurred within the first year. Autoimmunity emerged as the only predictive factor for dysfunction development (relative risk, 8.9), whereas sustained disease was significantly associated with male gender (P < 0.003). CONCLUSIONS: Both incident thyroid autoimmunity and dysfunction frequently occur in MS patients during IFN-beta therapy, particularly within the first year of treatment. Thyroid dysfunction is generally subclinical and transient in over than half of cases; preexisting or incident autoimmunity emerged as the only significant predictive factor for thyroid dysfunction development. Thyroid function and autoimmunity assessment is mandatory within the first year of IFN-beta therapy; thereafter, serum TSH measurement only in patients with thyroid disease could be sufficient.     

为我们的儿童而安全补碘

补碘预防碘缺乏性疾病的益处已不言而喻，但也发生甲状腺毒症和引起甲状腺功能减退症（甲减）的甲状腺炎等不良反应。碘致甲状腺炎以前的证据仅来自实验性研究、病理学检查和横断面流行病学调查。本期发表的滕卫平等在中国轻度碘缺乏、超足量碘补充和碘过量摄取地区的3个人群的研究已证实随着较高的碘摄取，甲状腺自身免疫和亚临床甲减的发病率呈轻度、但已有统计学意义的上升。然而，临床甲减的发病率并未见升高。这些发现再次从临床和公共卫生方面消除了人们的疑虑，证实了补碘方案对人类健康会产生巨大的效益而风险甚小。     

Thyroid disease in pregnancy and childhood

The subject of thyroid disease in pregnancy is receiving increasing attention from many scientific disciplines. Thyroid function in pregnancy is characterised by a T4 surge at 12 weeks declining thereafter. Serum thyroid hormone concentrations fall in the second half of pregnancy but there are few data on normal reference ranges. Fetal brain development depends on T4 transport into the fetus which in turn depends on sufficient maternal iodine supply. There is current concern that adequate iodisation is not present in large parts of Europe. There is increasing evidence that thyroid autoimmunity is associated with fetal loss but the mechanism is unclear and therapy requires carefully conducted studies. While hyperthyroidism in pregnancy is uncommon, effects on both mother and child are critical if untreated. The use of propylthiouracil is recommended together with measurement of TSH receptor antibodies at 36 weeks gestation. Women receiving thyroxine therapy for hypothyroidism or as suppressive therapy should have their dose increased by up to 50% during pregnancy. There are now substantial data to show deleterious effects on child IQ resulting from low maternal T4 (or high TSH) during gestation. Major advances in molecular biology have contributed to elucidation of many genetic causes of congenital hypothyroidism. However, the aetiology of the majority of cases is still unclear and further research is required. The presence of TPO antibodies in about 10% of pregnant women in early gestation is a predictor of an increased incidence of subclinical hypothyroidism during pregnancy and also of postpartum thyroid dysfunction. The latter condition occurs in 5-9% of women and 25-30% progress to permanent hypothyroidism. This review suggests that screening for thyroid function in early pregnancy and levothyroxine intervention therapy for maternal subclinical hypothyroidism should be considered but evidence is awaited. Screening for both thyroid dysfunction and thyroid antibodies ideally at a preconception clinic but certainly in early gestation is recommended.     

The thyroid during pregnancy: a physiological and pathological stress test

Pregnancy and the postpartum are times of marked and rapid change in the thyroid gland. Normal physiological changes include enhanced thyroid hormone production, modulation of thyroid hormone metabolism by placental deiodinases, and decreasing titers of thyroid antibodies in thyroid antibody positive women. Hyperemesis gravidarum is associated with suppressed thyroid stimulating hormone levels and free T4 elevations. Graves' disease typically becomes quiescent during pregnancy, followed by a postpartum flare. Women with pre-existing hypothyroidism frequently require an increase in their levothryoxine requirement in the 1(st) trimester, and subclinical hypothyroidism early in pregnancy is linked to both miscarriage and impaired neurological development in the unborn child. Postpartum thyroiditis occurs in 7.2% of women, and euthyroid women who are thyroid antibody positive in the 1(st) trimester of pregnancy have a doubling of the miscarriage rate.     

老年人甲状腺功能异常与心血管疾病

甲状腺功能异常与心血管疾病密切相关。老年人促甲状腺激素分布曲线向高水平方向偏移,因此,需应用年龄特异的参考范围判断甲状腺功能状态。近来,亚临床甲状腺疾病日益得到重视。研究表明亚临床甲状腺功能亢进（亚甲亢）可引起心脏结构和功能的改变,可引起房颤的发生率增加。而亚临床甲状腺功能减退（亚甲减）可能是心力衰竭、缺血性心脏病、全因死亡的一个潜在危险。异常甲状腺功能经纠正后,与甲亢和甲减相关的心血管疾病可得到缓解。基于老老年患者中亚临床甲减可能有保护作用,因此,亚临床甲状腺功能异常对心血管疾病的影响以及何种患者经过治疗可以获益,需要更多的循证医学的证据用以指导临床实践。     

开展亚临床甲状腺功能减退症的临床研究

亚临床甲状腺功能减退症 (甲减 )是一种常见的内分泌专业亚临床疾病 ,主要诊断依据是血清TSH水平增高 ,而血清FT4正常。亚临床甲减的主要不良后果是发展为临床甲减和促进缺血性心脏病的发生。影响亚临床甲减发展为临床甲减的主要因素有两个 :血清TSH水平和甲状腺自身抗体 ,两个因素有叠加作用。甲状腺激素替代治疗对于阻止亚临床甲减发展为临床甲减的效果尚不确切 ;亚临床甲减与高胆固醇血症、高血压、吸烟和糖尿病一样 ,构成动脉粥样硬化和心肌梗塞的独立危险因素 ,其对此两病的危险度分别为 1.9和 3 .1。甲状腺素纠正亚临床甲减对降低血清胆固醇有一定效果 ;妊娠妇女的亚临床甲减对后代的智力影响已经引起高度关注。我国一组根据对流行病学调查的结果 ,提出了血清TSH、甲状腺自身抗体 (TPOAb、TgAb)的正常值范围 ,以及与疾病相关的甲状腺自身抗体的切割点值 ,可供参考。     

High prevalence of thyroid autoimmunity and hypothyroidism in patients with psoriatic arthritis

OBJECTIVE:To evaluate the prevalence of thyroid disorders in a group of patients with psoriatic arthritis (PsA). METHODS: A complete thyroid investigation was carried out in 80 patients with PsA, in gender- and age-matched subjects (1:5) drawn from the general population (controls), and in 112 patients with rheumatoid arthrtitis (RA) with similar iodine intake. RESULTS: Anti-thyroid peroxidase antibodies (AbTPO), a hypoechoic thyroid, and subclinical hypothyroidism were significantly more frequent in women with PsA than in control women, and their frequency was similar to that in patients with RA (positive AbTPO titer 28%, 12%, and 31%; hypoechoic thyroid 31%, 16%, and 36%; subclinical hypothyroidism 25%, 8%, and 12%, respectively). Among men, positive AbTPO titers and a hypoechoic thyroid were found more frequently in the patients with PsA and RA than in controls (positive AbTPO titer 14%, 5%, and 2%; hypoechoic thyroid 16%, 10%, and 3%, respectively). All patients with PsA with subclinical hypothyroidism had polyarticular involvement (p 相似文献   

甲状腺过氧化物酶抗体检测的临床意义

甲状腺过氧化物酶表达于甲状腺滤泡细胞表面,主要参与甲状腺激素的合成与释放,并与细胞介导的细胞毒效应有关.甲状腺过氧化物酶能诱导机体产生高亲和力的IgG抗体(TPOAb)与甲状腺过氧化物酶特异的T淋巴细胞,分别参与甲状腺的浸润与破坏.TPOAb定量检测最常用的方法为酶联免疫吸附法.与TPOAb相关的疾病包括恶性贫血、结缔组织病、糖尿病、炎症性肠病、情感障碍以及一些妇产科疾病如流产、不孕、体外受精失败、早产、产后甲状腺炎等.正确认识TPOAb检测的指征,如对甲状腺肿以及Graves病或桥本甲状腺炎等自身免疫性甲状腺疾病的诊断和鉴别诊断、预测亚临床甲状腺疾病发生甲状腺功能减退症的风险等具有十分重要的临床意义.     

Does Treating Subclinical Hypothyroidism Improve Markers of Cardiovascular Risk?

Subclinical hypothyroidism is defined as an elevated serum thyroid-stimulating hormone (TSH) level in the face of normal free thyroid hormone values. The overall prevalence of subclinical hypothyroidism is 4-10% in the general population and up to 20% in women aged >60 years. The potential benefits and risks of therapy for subclinical hypothyroidism have been debated for 2 decades, and a consensus is still lacking. Besides avoiding the progression to overt hypothyroidism, the decision to treat patients with subclinical hypothyroidism relies mainly on the risk of metabolic and cardiovascular alterations. Subclinical hypothyroidism causes changes in cardiovascular function similar to, but less marked than, those occurring in patients with overt hypothyroidism. Diastolic dysfunction both at rest and upon effort is the most consistent cardiac abnormality in patients with subclinical hypothyroidism, and also in those with slightly elevated TSH levels (>6 mIU/L). Moreover, mild thyroid failure may increase diastolic blood pressure as a result of increased systemic vascular resistance. Restoration of euthyroidism by levothyroxine replacement is generally able to improve all these abnormalities. Early clinical and autopsy studies had suggested an association between subclinical hypothyroidism and coronary heart disease, which has been subsequently confirmed by some, but not all, large cross-sectional and prospective studies. Altered coagulation parameters, elevated lipoprotein (a) levels, and low-grade chronic inflammation are regarded to coalesce with the hypercholesterolemia of untreated patients with subclinical hypothyroidism to enhance the ischemic cardiovascular risk. Although a consensus is still lacking, the strongest evidence for a beneficial effect of levothyroxine replacement on markers of cardiovascular risk is the substantial demonstration that restoration of euthyroidism can lower both total and low-density lipoprotein-cholesterol levels in most patients with subclinical hypothyroidism. However, the actual effectiveness of thyroid hormone substitution in reducing the risk of cardiovascular events remains to be elucidated. In conclusion, the multiplicity and the possible reversibility of subclinical hypothyroidism-associated cardiovascular abnormalities suggest that the decision to treat a patient should depend on the presence of risk factors, rather than on a TSH threshold. On the other hand, levothyroxine replacement therapy can always be discontinued if there is no apparent benefit. Levothyroxine replacement therapy is usually safe providing that excessive administration is avoided by monitoring serum TSH levels. However, the possibility that restoring euthyroidism may be harmful in the oldest of the elderly population of hypothyroid patients has been recently raised, and should be taken into account in making the decision to treat patients with subclinical hypothyroidism who are aged >85 years.     

Prevalence of hypothyroidism and Graves disease in sarcoidosis

BACKGROUND: The association of sarcoidosis (S) and thyroid autoimmunity has been reported by several studies in a wide range of variability. The aim of our study was to evaluate the prevalence of clinical and subclinical thyroid disorders in patients with S vs gender-matched and age-matched control subjects. METHODS: Thyroid hormones and antithyroid antibodies, thyroid ultrasonography and fine-needle aspiration were performed in 111 patients with S who had been consecutively referred to the Respiratory Pathophysiology Section of the University of Pisa, and the results were compared to 333 gender-matched and age-matched control subjects from the same geographic area. RESULTS: The odds ratio for subclinical hypothyroidism for female patients with S vs control subjects was 2.7 (95% confidence interval [CI], 1.3 to 5.9); for anti-thyroid peroxidase antibody titer (AbTPO) positivity, 2.2 (95% CI, 1.2 to 3.9); and for thyroid autoimmunity, 1.9 (95% CI, 1.1 to 3.2). The mean values of thyroid-stimulating hormone and AbTPO were higher in female S patients than in control subjects (p < 0.01). A significantly higher prevalence of clinical hypothyroidism (four patients) and Graves disease (three patients) was observed in female S patients than in control subjects (none; p = 0.005 and 0.0026, respectively). Two cases of papillary thyroid cancer were detected in S patients. No significant difference between S patients and control subjects was detected for free triiodothyronine and thyroxine, antithyroglobulin autoantibodies, thyroid volume and nodularity, and subclinical hyperthyroidism. CONCLUSIONS: Thyroid function, AbTPO antibodies, and ultrasonography should be tested as part of the clinical profile in female S patients. Subjects who are at high risk (female subjects, those with positive AbTPOs, and those with hypoechoic and small thyroid) should have thyroid function follow-up and appropriate treatment in due course.     

Thyroid disorders and hypercoagulability

Various abnormalities of coagulation and fibrinolysis, ranging from subclinical laboratory abnormalities to clinically significant disorders of hemostasis, but rarely major hemorrhage or thromboembolism, may occur in patients with thyroid diseases. This review discusses the relationships between thyroid dysfunction and the coagulation/fibrinolytic system. According to the recent literature, most of the coagulation/fibrinolytic abnormalities associated with thyroid dysfunction are the consequences of direct effects of thyroid hormones on the synthesis of various hemostatic parameters. Thyroid autoimmunity may also modify the processes of secondary hemostasis. Hyperthyroidism is generally associated with hypercoagulability and hypofibrinolysis, whereas the hemostatic profile in hypothyroidism depends on the severity of the disease. Both hypercoagulable and hypocoagulable states including increased fibrinolytic activity have been reported in hypothyroidism. Few data are available on hemostasis in subclinical thyroid diseases. In conclusion, adequate further prospective clinical studies of high quality including a larges series of patients are needed to explain the degree and type of coagulation/fibrinolytic abnormalities in patients with thyroid diseases.     

Natural course of autoimmune thyroiditis after elimination of iodine deficiency in northwestern Greece.

We have previously reported the elimination of iodine deficiency and increasing prevalence of autoimmune thyroiditis (AIT) among schoolchildren in northwestern Greece. This study followed up 29 children (12-18 years old) with AIT for 5 years to track its course in the postiodination era. At diagnosis, thyroid peroxidase autoantibodies (TPOAbs) were positive in 25 children (86%) and became positive in all children during follow-up. Thyroglobulin autoantibodies (TgAbs) were positive in 17 children at diagnosis (59%) and became positive in 3 more children (69%). Both antibody types increased by the end of the observation period (p < 0.005). Regarding thyroid function, 7 children (24%) at diagnosis had subclinical hypothyroidism that persisted and 4 more children developed subclinical hypothyroidism during the study period (38%). Only 5 of these children (45%) had positive TgAbs. There was an increase in thyrotropin (TSH) so that at the end of the study all children had TSH greater than 2.5 mU/L but none developed overt hypothyroidism. Thyroid hypoechogenicity that increased over time was seen in all children, especially in those with subclinical hypothyroidism. In conclusion, both antibody types increased in frequency and level, but TPOAbs were the predominant autoimmunity marker predictive of impending thyroid failure in children with AIT, as was thyroid hypoechogenicity on ultrasound.     

Coagulation and fibrinolysis in thyroid dysfunction

Various abnormalities of hemostasis, ranging from subclinical laboratory abnormalities to clinically significant disorders of hemostasis, and rarely major hemorrhage or thromboembolism, may occur in patients with thyroid diseases. The objective of this review is to discuss the relationships between thyroid dysfunction and hemostasis (primary hemostasis and coagulation/fibrinolytic system). According to the recent literature, most of the hemostatic abnormalities associated with thyroid dysfunction are the consequences of direct effects of thyroid hormones on the synthesis of various hemostatic parameters. Thyroid autoimmunity may also modify the processes of primary and secondary hemostasis. We have concluded that hyperthyroidism is generally associated with hypercoagulability and hypofibrinolysis, whereas the hemostatic profile in hypothyroidism depends on the severity of the disease. As few data are available on hemostasis in subclinical thyroid disease, further studies on this subject are needed.     

Optimal management of hypothyroidism,hypothyroxinaemia and euthyroid TPO antibody positivity preconception and in pregnancy

Normal physiological changes of pregnancy warrant the need to employ gestation specific reference ranges for the interpretation of thyroid function tests. Thyroid hormones play crucial roles in foetal growth and neurodevelopment which are dependent on adequate supply of maternal thyroid hormones from early gestation onwards. The prevention of significant adverse obstetric and neurodevelopmental outcomes from hypothyroidism requires a strategy of empirical levothyroxine dose increases and predictive dose adjustments in pregnancy combined with regular thyroid function testing, starting before pregnancy and until the postpartum period. Subclinical hypothyroidism has been associated with an increased risk of pregnancy loss and neurocognitive deficits in children, especially when diagnosed before or during early pregnancy. Whilst trials of levothyroxine replacement for mild hypothyroidism in pregnancy have not indicated definite evidence of improvements in these outcomes, professional guidelines recommend treatment, especially if evidence of underlying thyroid autoimmunity is present. Studies of isolated hypothyroxinaemia in pregnancy have shown conflicting evidence with regards to adverse obstetric and neurodevelopmental outcomes and no causative relationships have been determined. Treatment of this condition in pregnancy may be considered in those with underlying thyroid autoimmunity. Whilst the evidence for a link between the presence of anti‐TPO antibodies and increased risks of pregnancy loss and infertility is compelling, the results of ongoing randomized trials of levothyroxine in euthyroid women with underlying autoimmunity are currently awaited. Further studies to define the selection of women who require levothyroxine replacement and to determine the benefits of a predictive dose adjustment strategy are required.