Transient Hypothyroxinemia in Severe Hypertensive Disorders of Pregnancy

Effect of Levothyroxine on Pregnancy Outcomes in Pregnant Women With Hypothyroxinemia: An Interventional Study

CONTEXT

Adverse maternal outcomes and perinatal complications are associated with maternal hypothyroidism. However, the utility of levothyroxine (L-T4) in the treatment of pregnant women with hypothyroxinemia is unclear.

OBJECTIVE

This study aimed to evaluate the effects of L-T4 on maternal and perinatal outcomes in pregnant women with hypothyroxinemia.

METHODS

The nonrandomized interventional study was conducted at Shanghai First Maternity and Infant Hospital, Punan Hospital of Shanghai, and Beicai Community Health Center of Shanghai. The pregnant women with hypothyroxinemia from the first trimester were enrolled and divided into treatment and control groups. 463 taking L-T4 and 501 not administering L-T4 were analyzed in the study. All participants were screened for TPOAB/TGAB antibody status.

MAIN OUTCOME

The primary outcome of the study was the hypertensive disorder of pregnancy (HDP), measured as the proportion of HDP. In addition to this primary outcome, some secondary outcomes will be measured: miscarriage, gestational diabetes mellitus, premature rupture of membranes, placental abruption, intrahepatic cholestasis of pregnancy, fetal distress, macrosomia, and neonates admitted to the neonatal intensive care unit (NICU). The effects of L-T4 on the incidence of adverse pregnancy outcomes and perinatal complications were compared.

RESULTS

Multivariate logistic regression analysis showed that L-T4 treatment (adjusted odds ratio = 1.78 [95% CI = 1.00-3.16], p = 0.04) significantly reduced the incidence of miscarriage. Otherwise, lower neonates admitted to the NICU were strongly associated with the L-T4 group (adjusted odds ratio = 1.36 [95% CI = 1.01 - 1.83], p = 0.04). There were no significant differences in the incidence rates of other adverse maternal outcomes and perinatal complications between pregnant women with hypothyroxinemia receiving and those not receiving L-T4 treatment.

CONCLUSION

The incidence of HDP was not significantly reduced using L-T4 in pregnant women with hypothyroxinemia. The results of this study also showed that L-T4 treatment significantly reduced the miscarriages rate and the proportion of newborns admitted to the NICU.

Controversies in endocrinology: On the need for universal thyroid screening in pregnant women

There is a well-known controversy among scientific societies regarding the recommendation to screen for thyroid dysfunction (TD) during pregnancy. Although several studies have shown an association between maternal subclinical hypothyroidism and/or hypothyroxinemia with obstetric problems and/or neurocognitive impairment in the offspring, there is only limited evidence on the possible positive effects of thyroxine (T4) treatment in such cases. Despite the scarcity of this evidence, there is a widespread agreement among clinicians on the need for treatment of clinical hypothyroidism during pregnancy and the risks that could arise due to therapeutic abstention. As maternal TD is a quite prevalent condition, easily diagnosed and for which an effective and safe treatment is available, some scientific societies have proposed to assess thyroid function during the first trimester of pregnancy and ideally before week 10 of gestational age. Given the physiologic changes of thyroid function during pregnancy, hormone assessment should be performed using trimester-specific reference values ideally based on locally generated data as geographic variations have been detected. Screening of TD should be based on an initial determination of TSH performed early during the first trimester and only if abnormal should it be followed by either a free or total T4 measurement. Furthermore, adequate iodine supplementation during pregnancy is critical and if feasible it should be initiated before the woman attempts to conceive.

[Detection of thyroid dysfunction in pregnant women: universal screening is justified]

There is a controversy among different scientific societies in relation to the recommendations on whether universal screening for the detection of thyroid dysfunction during gestation should be performed or not. Although various studies have shown an association between subclinical hypothyroidism or hypothyroxinemia with obstetric problems and/or neurocognitive impairment in the offspring, no evidence on the possible positive effects of treatment of such conditions with thyroxin has been demonstrated so far. However, there is a general agreement about the need for treatment of clinical hypothyroidism during pregnancy and the risks of not doing so. Because it is a common, easily diagnosed and effectively treated disorder without special risk, the working Group of Iodine Deficiency Disorders and Thyroid Dysfunction of the Spanish Society of Endocrinology and Nutrition and Spanish Society of Gynaecology and Obstetrics recommends an early evaluation (before week 10) of thyroid function in all pregnant women. Given the complex physiology of thyroid function during pregnancy, hormone assessment should be performed according to reference values for each gestational trimester and generated locally in each reference laboratory. Thyrotropin determination would be sufficient for screening purposes and only if it is altered, free thyroxin or total thyroxin would be required. Adequate iodine nutrition is also highly recommended before and during pregnancy to contribute to a normal thyroid function in the pregnant women and fetus.

Correlation between the TSHRc-Asp727Glu polymorphism and plasma thyroid stimulating hormone levels in Romanian preeclamptic women

AIM

To analyze the influence of thyroid stimulating hormone (TSH) levels and/or the Asp727Glu polymorphism on the severity and perinatal outcome of preeclampsia.

METHODS

Forty-nine women with preeclampsia and 58 normal pregnant women were genotyped for the TSHRc-Asp727Glu polymorphism using PCR-RFLP methods. The plasma TSH levels were measured by ELISA method.

RESULTS

Fourteen (77.78%) women of 18 pregnant women with abnormal TSH levels had preeclampsia compared to 35 (39.33%) of 89 pregnant women with normal TSH levels who had preeclampsia (OR 5.4, p = 0.003). The mean TSH levels were 2.13 ± 1.44 μU/ml, 2.47 ± 2.03 μU/ml and 4.27 ± 2.75 μU/ml in women with pregnancy induced hypertension (PIH), mild and severe preeclampsia, respectively. OR for PIH and mild preeclampsia was 1.08 (p = 1) and 9.45 (p = 0.06), respectively, in association with the Asp/Asp genotype. All women with severe preeclampsia had the Asp/Asp genotype. The risk for preeclampsia in association with TSH > 4 μU/ml and Asp/Asp genotype is 20.8 (p < 0.01). Preeclamptic women with TSH levels > 4 μU/ml and the Asp/Asp genotype delivered earlier (weeks, 34.92 ± 4.33 vs. 36.6 ± 3.21, p = 0.3) neonates with lower birth weight (grams, 2361.54 ± 1155.81 vs. 3000 ± 1072.38, p = 0.3) than preeclamptic women with TSH levels  < 4 μU/ml and the Asp/Glu genotype.

CONCLUSIONS

Higher TSH levels and/or the TSHRc-Asp727Glu polymorphism represent risk factors for preeclampsia and could be correlated with the severity of preeclampsia.

Thyroid function and pregnancy: before, during and beyond

Thyroid disturbances are common in women during the reproductive years of their lives. Autoimmunity and altered iodine status together account for a high proportion of the abnormalities. Autoimmune thyroid disease is present in around 4% of young females, and up to 15% are at risk because they are thyroid antibody-positive. There is a strong relationship between thyroid immunity on the one hand and infertility, miscarriage, and thyroid disturbances in pregnancy and postpartum on the other hand. Suboptimal iodine status affects a large proportion of the world's population, and pregnancy further depletes iodine stores. There is controversy surrounding the degree to which iodine should be supplemented and the duration of supplementation. Recent studies have helped to clarify the relationship between maternal thyroid status and neuropsychological development of the child. The role of other environmental factors including smoking and selenium status is also now recognised. Universal screening for thyroid hormone abnormalities is not routinely recommended at present. However, measurement of thyroid function and autoantibodies should certainly be considered in those who are at high risk of thyroid disease and in those whose pregnancy is otherwise high risk. The practicing clinician needs to be aware of the thyroid changes which accompany pregnancy.

Trials with thyroid hormone in preterm infants: clinical and neurodevelopmental effects

A large number of articles exist on thyroid hormone function and its clinical correlates, but only a few exist on trials with thyroid hormones in premature infants. Most of these trials had clinical short-term endpoints, while only one trial had a long-term neurodevelopmental endpoint. None of the trials reported changes in mortality and morbidities. A trend toward a lower occurrence of patent ductus arteriosus is found in thyroid hormone treated infants. A gestational age-dependent effect of thyroxine on neurodevelopmental outcome was found in post-hoc subgroup analyses up until the age of 10 years. Thyroxine treatment was associated with improved mental, motor, and neurological outcomes in infants <28 weeks gestation, but with worse mental and neurological outcome in infants of 29 weeks gestation. Future trials should focus on neurodevelopmental outcomes. Continuous administration of thyroid hormone may be more effective than bolus administration.

Thyroid insufficiency during pregnancy: complications and implications for screening

In 2007, clinical practice guidelines concerning the management of thyroid dysfunction during pregnancy and postpartum were published in the Journal of Clinical Endocrinology and Metabolism. They were elaborated on by a panel of experts, representative of the Latin American Thyroid Society, the Asia and Oceania Thyroid Society, the American Thyroid Association, the European Thyroid Association, the American Association of Clinical Endocrinologists and the Endocrine Society. In women not known to have thyroid dysfunction, universal screening during pregnancy is not recommended, but thyroid function tests are advised in those with prior therapeutic head or neck irradiation, a history of preterm delivery, in cases of infertility and in the presence of risk factors for thyroid disease. Risks factors for thyroid dysfunction are considered as a personal or family history of thyroid diseases, presence of thyroid antibodies (when known), personal history of autoimmune diseases and the presence of signs or symptoms suggesting hypo- or hyperthyroidism. In this review, we summarize the modifications of the pituitary-thyroid axis during pregnancy, with particular attention on thyroid insufficiency. We consider the most important risk factors for thyroid dysfunction and focus our attention on the complications for the progeny, deriving from a condition of maternal thyroid impairment. We will discuss the matters in favor of or against a thyroid-screening program at the beginning of pregnancy.