Management of thyroid dysfunction during pregnancy and postpartum: an Endocrine Society Clinical Practice Guideline

Unmasking of Gitelman Syndrome during Pregnancy in an Adolescent with Thyrotoxic Crisis

BACKGROUND

Gitelman syndrome (GS) is an inherited salt-losing renal tubulopathy characterized by hypokalemic metabolic alkalosis with hypomagnesemia and hypocalciuria. Patients can be asymptomatic until late adolescence or adulthood, and hence may be discovered incidentally during presentation with other illnesses. GS has been described in association with thyroid disorders and should be considered in patients with hyperthyroidism and persistent hypokalemia, especially in those with associated hypomagnesemia and hypocalciuria.

CASE SUMMARY

In this report, we describe an 18-year-old female who presented with hyperemesis gravidarum and thyrotoxicosis, and was incidentally found to have GS, confirmed by the sequence analysis of SLC12A3. Conclusions. Thyroid dysfunctions, such as hypothyroidism, thyrotoxicosis, and thyroid nodules, may develop during pregnancy. A structural homology between the beta-human chorionic gonadotropin and thyroid stimulating hormone molecules, as well as their receptors is probably the basis for the transient thyrotoxicosis crisis during pregnancy. Since hyperemesis in pregnancy can also lead to hypokalemia and alkalosis, a high index of suspicion for GS during pregnancy is required for timely diagnosis and management.

Relationship between Thyroid Status during the First Trimester of Pregnancy and Neonatal Well-Being

Iodine is an essential micronutrient for the synthesis of thyroid hormones. The proper functioning of the thyroid axis is essential for the normal development of the nervous system, especially in the first trimester of gestation. The aim of the present study was to analyze the perinatal outcomes, anthropometry, and APGAR test scores of newborns and to relate them to maternal thyroid status. A total of 190 newborns participated in the study. No correlation was found between thyroid stimulating hormone (TSH) and maternal ioduria values in the first trimester of gestation with the weight or length of the newborn, or the APGAR score at one minute after birth. However, we found significant differences between the APGAR scores of children whose mothers had an iodine sufficiency level in the first trimester compared to the children of mothers with iodine deficiency. Similarly, the APGAR scores of children whose mothers had a TSH > 4 have significantly better APGAR scores than the children of mothers with a TSH < 4. Likewise, we found significant differences between the measurements of the newborns depending on whether their mothers smoked. The children of mothers who took iodine supplements or iodized salt obtained the highest APGAR score at one and five minutes after birth. It is essential to focus on recommending adequate consumption of iodine supplements and iodized salt prior to gestation and at least during the first trimester to achieve better fetal well-being.

Reference Values of Thyroid Hormones During the First Trimester of Pregnancy in Valencian Community (Spain) and Their Relationship with Iodine Intake

Thyroid hormones require special monitoring during the first trimester of gestation. Local reference values should be applied if available, especially in iodine-deficient areas, as generalized iodine supplementation is controversial. The aim of the present study was to establish thyroid stimulating hormone (TSH) and free thyroxine (FT4) reference values in the first trimester of gestation in the Valencian community (Spain) and relate them to iodine intake. A total of 261 healthy pregnant women participated in the study. The calculated reference values were 0.128-4.455 mIU/L for TSH and 0.9-1.592 ng/dL for FT4. The upper TSH reference value for pregnant women in the first trimester in our environment was similar to the latest American Thyroid Association (ATA) recommendation (4 mIU/L). The mean TSH value was significantly lower in smokers, and there were no significant differences when analyzing the influence of iodine supplementation, although the low duration of supplement intake needs to be taken into consideration. Ioduria levels (median 57 µg/L) confirmed iodine deficiency. We found statistically significant differences in ioduria levels among patients who consumed iodized salt and iodine supplements and those who did not. It is essential to focus on recommending adequate consumption of iodized salt and iodine supplements prior to gestation and at least during the first trimester to avoid possible maternal thyroid dysfunction and perinatal complications.

Screening strategies for thyroid disorders in the first and second trimester of pregnancy in China

BACKGROUND

Thyroid dysfunction during pregnancy is associated with multiple adverse outcomes, but whether all women should be screened for thyroid disorders during pregnancy remains controversial.

OBJECTIVE

To evaluate the effectiveness of the targeted high risk case-finding approach for identifying women with thyroid dysfunction during the first and second trimesters of pregnancy.

METHODS

Levels of thyroid stimulating hormone (TSH), free thyroxine (FT4), and thyroid peroxidase antibodies (TPOAb) were measured in 3882 Chinese women during the first and second trimester of pregnancy. All tested women were divided into the high risk or non-high risk groups, based on their history, findings from physical examination, or other clinical features suggestive of a thyroid disorder. Diagnosis of thyroid disorders was made according to the standard trimester-specific reference intervals. The prevalence of thyroid disorders in each group was determined, and the feasibility of a screening approach focusing exclusively on high risk women was evaluated to estimate the ability of finding women with thyroid dysfunction.

RESULTS

The prevalence of overt hypothyroidism or hyperthyroidism in the high risk group was higher than in the non-high risk group during the first trimester (0.8% vs 0, χ2 = 7.10, p = 0.008; 1.6% vs 0.2%, χ2 = 7.02, p = 0.008, respectively). The prevalence of hypothyroxinemia or TPOAb positivity was significantly higher in the high risk group than in the non-high risk group during the second trimester (1.3% vs 0.5%, χ2 = 4.49, p = 0.034; 11.6% vs 8.4%, χ2 = 6.396, p = 0.011, respectively). The total prevalence of hypothyroidism or hyperthyroidism and the prevalence of subclinical hypothyroidism or hyperthyroidism were not statistically different between the high risk and non-high risk groups, for either the first or second trimester.

CONCLUSION

The high risk screening strategy failed to detect the majority of pregnant women with thyroid disorders. Therefore, we recommend universal screening of sTSH, FT4, and TPOAb during the first trimester and second trimester of pregnancy.

Thyroid autoantibodies in pregnancy: their role, regulation and clinical relevance

Autoantibodies to thyroglobulin and thyroid peroxidase are common in the euthyroid population and are considered secondary responses and indicative of thyroid inflammation. By contrast, autoantibodies to the TSH receptor are unique to patients with Graves' disease and to some patients with Hashimoto's thyroiditis. Both types of thyroid antibodies are useful clinical markers of autoimmune thyroid disease and are profoundly influenced by the immune suppression of pregnancy and the resulting loss of such suppression in the postpartum period. Here, we review these three types of thyroid antibodies and their antigens and how they relate to pregnancy itself, obstetric and neonatal outcomes, and the postpartum.

Thyroid hormone testing by tandem mass spectrometry

In the euthyroid person, absolute free thyroxine concentrations remain constant and correlate with the tissue hormone level, its biologic effect and the metabolic status of the patient. However, most circulating thyroid hormone is bound to plasma proteins and only a minute amount is in the unbound free form. Studies have shown that current free thyroxine immunoassays are binding protein dependent. Novel high-performance liquid chromatography tandem mass spectrometry (LC/MS/MS) methods have successfully dealt with problems inherent in many immunoassays for thyroid hormones and afforded improved specificity and accuracy in thyroid hormone measurements. We emphasize problems with thyroid hormone testing employing immunoassays including direct and indirect thyroid hormone immunoassays, sample processing, methods of free hormone separation and review the emerging role of liquid chromatography-tandem mass spectrometry in thyroid hormone testing. The latest generation of tandem mass spectrometers has superior limits of quantification, permitting omission of previously employed derivatization steps. Liquid chromatography-tandem mass spectrometry affords the specificity, precision, and limits of quantification necessary for the reliable measurement of thyroid hormones, enhancing diagnostic capabilities, and affording the profiles of the iodothyronines and thyronamines. These methods are especially important in states of disease and during pregnancy when protein binding is a factor that interferes with other methods for thyroid hormone analysis.

J, Hajdú J. Severe circulatory insufficiency in a patient with neonatal hyperthyroidism

A szerzők egy Basedow–Graves-kór miatt korábban thyreoidectomián átesett, kezeletlen anya koraszülöttjének esetét ismertetik. Gondozatlan terhességből magzati tachycardia, fenyegető intrauterin asphyxia miatt sürgős császármetszéssel született a 33. hétnek megfelelő érettségű, 1350 gramm súlyú, dysmaturus (testsúlypercentil <10), nagy nyaki strumával bíró koraszülött. Az újszülött respiratoricus elégtelenség miatt konvencionális és magas frekvenciás gépi lélegeztetésben részesült, súlyos tachycardia (>180/perc), cardialis decompensatio miatt béta-blokkoló, digoxin- és dobutaminterápiát igényelt. Kivizsgálása során cardiomegalia, pericardialis folyadékgyülem, súlyos tüdőhypoplasia, mitralis és tricuspidalis insufficientia, hepatosplenomegalia igazolódott. A pajzsmirigy-szabadhormonok szintje többszörösen meghaladta a referenciaértéket (fT4: > 6 ng/dl, fT3: > 30 pg/ml), a TSH-szint ugyanakkor 0 volt. Légzéstámogatást 7, keringéstámogatást 10 napig igényelt, propranolol- mellett K-jodid-kezelésben részesült. Tachycardiája mérséklődött, a béta-blokkoló kezelést csökkentett adagban kapta tovább, pajzsmirigyhormonszintjei fokozatosan a normális tartományba kerültek. A szerzők felhívják a figyelmet arra, hogy a Basedow–Graves-kórban szenvedő anya újszülöttjénél jelentős súlybeli, növekedésbeli elmaradás, súlyos keringési elégtelenség, thyreotoxicosis tünetei alakulhatnak ki, és hangsúlyozzák az anyai hormon-, valamint antitestszintek nyomon követésének jelentőségét.