Thyroid function inside and outside of pregnancy: what do we know and what don't we know?

Iodized Salt May Not Be Sufficient to Guarantee an Adequate Iodine Intake in Pregnant Women

Adequate iodine intake is of crucial importance in pregnancy to meet the thyroid hormone needs of both mother and fetus. In the present study, undertaken as a part of the surveillance actions following the introduction in Italy of a national salt iodination program in 2005, the iodine intake was investigated in 123 pregnant women and 49 control women living in the same area of central Italy. All the participants were screened for urinary iodine concentration (UIC), serum level of thyrotropin, free-thyroxine, free-triiodothyronine, and thyroid volume. Moreover, they were provided with a questionnaire on the use of iodine-containing salt or supplements. Control women had a median UIC of 102 µg/L, consistent with an iodine sufficiency, while in pregnant women the median UIC value was 108 µg/L, lower than the endorsed UIC of 150 µg/L. In addition, pregnant women showed a significantly increased median thyroid volume compared to controls. Interestingly, the median UIC did not differ between pregnant women not using iodine-containing salt or supplements and those regularly consuming iodized salt alone, while pregnant women with a daily intake of iodine-containing supplements had an adequate median UIC (168 µg/L). In conclusion, the data reported here showed that pregnant women and their fetuses are still exposed to the detrimental effects of iodine deficiency and that the consumption of iodine-containing supplements should be recommended in pregnancy.

Maternal hypothyroidism and its effect on placental histopathology in singleton live births resulting from in vitro fertilization treatment

We aimed to examine the impact of maternal hypothyroidism on placental pathology and perinatal outcomes in singleton live births resulting from IVF, using medical records of IVF births between 2009 and 2017 at a tertiary hospital. The primary outcomes included anatomical, inflammation, vascular malperfusion, and villous maturation placental features. Secondary outcomes included foetal, maternal, perinatal, and delivery complications. There were 1,057 live births, of which 103 (9.7%) and 954 (90.3%) were in the study and control groups, respectively. Patients in the study group were more likely to have diabetes mellitus, polycystic ovarian syndrome, gestational diabetes mellitus, and non-reassuring foetal heart rate (NRFHR) tracing during delivery. After adjustment for potential confounding factors, hypothyroidism was significantly associated with the bilobed placenta (aOR 4.1; 95% CI 1.2-14.3), retroplacental haematoma (aOR 2.4; 95% CI 1.2-4.9), decidual arteriopathy (aOR 2.0; 95% CI 1.2-4.1) and subchorionic thrombi (aOR 2.4; 95% CI 1.3-5.0). Additionally, there was a statistically significant relationship with NRFHR tracing. The incidence of acute chorioamnionitis and severe foetal inflammatory response was higher in the study group. In conclusion, the placental histopathology patterns of singleton IVF live births show that maternal hypothyroidism has a significant impact on adverse perinatal outcomes.

The Thyroid Hormone Axis and Female Reproduction

Thyroid function affects multiple sites of the female hypothalamic-pituitary gonadal (HPG) axis. Disruption of thyroid function has been linked to reproductive dysfunction in women and is associated with menstrual irregularity, infertility, poor pregnancy outcomes, and gynecological conditions such as premature ovarian insufficiency and polycystic ovarian syndrome. Thus, the complex molecular interplay between hormones involved in thyroid and reproductive functions is further compounded by the association of certain common autoimmune states with disorders of the thyroid and the HPG axes. Furthermore, in prepartum and intrapartum states, even relatively minor disruptions have been shown to adversely impact maternal and fetal outcomes, with some differences of opinion in the management of these conditions. In this review, we provide readers with a foundational understanding of the physiology and pathophysiology of thyroid hormone interactions with the female HPG axis. We also share clinical insights into the management of thyroid dysfunction in reproductive-aged women.

Persistent Thyroid Carcinoma and Pregnancy: Outcomes in an Italian Series and Review of the Literature

Scanty data are available on the progression risk in patients with persistent thyroid cancer (TC) before pregnancy. We aimed to evaluate this topic in our series and to review available literature data. This was a retrospective study performed in a tertiary care Italian TC center. We included 8 patients with persistent papillary TC who became pregnant after initial treatments (mean time interval of 62 months). Seven patients had the structural disease (lung and/or neck node metastases), while one patient had biochemical persistence. During a mean follow-up of 97 months, none of the patients showed disease progression either during pregnancy or during a follow-up of at least 12 months after delivery, and no additional treatments were needed. A sequential biochemical evaluation showed that thyroglobulin levels can significantly increase during pregnancy, returning to preconception levels after delivery. In conclusion, our data confirm that pregnancy is not associated with disease progression in patients with stable local and/or distant persistence before conception. Thus, pregnancy should not be contraindicated in metastatic women, although a precise clinical characterization, including the disease stage at diagnosis, the ATA risk class, and the dynamic risk stratification, should be conducted before conception.

Relationship between Maternal Vitamin D Levels and Adverse Outcomes

Vitamin D (VD), a fat-soluble vitamin, has a variety of functions that are important for growth and development, including regulation of cell differentiation and apoptosis, immune system development, and brain development. As such, VD status during pregnancy is critical for maternal health, fetal skeletal growth, and optimal pregnancy outcomes. Studies have confirmed that adverse pregnancy outcomes, such as preeclampsia, low birth weight, neonatal hypocalcemia, poor postnatal growth, skeletal fragility, and increased incidence of autoimmune diseases, can be associated with low VD levels during pregnancy and infancy. Thus, there is growing interest in the role of VD during pregnancy. This review summarizes the potential adverse health outcomes of maternal VD status during pregnancy for both mother and offspring (gestational diabetes mellitus, hypertensive gestational hypertension, intrauterine growth restriction, miscarriage, stillbirth, and preterm birth) and discusses the underlying mechanisms (regulation of cytokine pathways, immune system processing, internal secretion, placental function, etc.) of VD in regulating each of the outcomes. This review aims to provide a basis for public health intervention strategies to reduce the incidence of adverse pregnancies.

Pregnancy has no significant impact on the prognosis of differentiated thyroid cancer

OBJECTIVE

To evaluate the impact of pregnancy on differentiated thyroid carcinomas (DTC) behavior.

METHODS

Retrospective study of patients diagnosed with DTC before or during pregnancy and treated with standard therapy. In women diagnosed with DTC before pregnancy, we evaluated the occurrence of progression according to categories of response to therapy based on imaging and non-stimulated thyroglobulin (TG) levels.

RESULTS

Of 96 analyzed patients, 76 became pregnant after DTC treatment and 20 were diagnosed with DTC during pregnancy. Among women who became pregnant after a DTC diagnosis, no difference was observed regarding response to therapy before and after pregnancy. Disease progression after pregnancy was documented in six of these patients, while seven of them presented progression before pregnancy but were only treated after delivery. Patients with DTC diagnosed during pregnancy had a higher rate of distant metastases at diagnosis (30%) compared with the patients who became pregnant after DTC diagnosis (9.2%, p = 0.01).

CONCLUSION

Pregnancy had no impact on the natural course of DTC. Disease progression after pregnancy was limited and probably related to more aggressive disease and higher risk stratification at diagnosis. Still, mild disease progression may have occurred asymptomatically in some patients.

Endocrine disrupting chemicals and thyroid hormone action

Thyroid hormones (predominantly thyroxine, T4, and triiodothyronine, T3) are essential for normal development and for adult physiology. There are several challenges, however, that make identifying chemicals that produce adverse effects by interfering with the thyroid system difficult. First, individual variability in serum concentrations of thyroid hormones represent only about 10% of the population reference range that is considered to be "normal." This means that populations studies evaluating the relationship between chemical exposure and serum thyroid hormones must be large enough to overcome this internal variance. In addition, we know that there are chemicals that do not produce changes in thyroid hormone levels, but nevertheless impact thyroid signaling in target tissues. A good example is that of polychlorinated biphenyls (PCBs). PCB exposure during development are clearly associated with cognitive deficits in humans. But PCB exposure isn't uniformly associated with a reduction in serum thyroid hormone in human populations despite mechanistic studies showing that PCBs reduce serum T4 in animals. In contrast, perchlorate is a chemical that inhibits iodide uptake, thereby reducing thyroid hormone synthesis and serum hormone levels. Human studies have been variable in identifying a relationship between thyroid hormone and perchlorate exposure, but studies also show that dietary iodine, cigarette smoking and other factors can modify this relationship. The conclusion is that identifying chemicals that interfere with thyroid hormone could depend on in vitro analysis of chemicals that interact with different proteins important for thyroid hormone to function properly.

Positive Impact of Levothyroxine Treatment on Pregnancy Outcome in Euthyroid Women with Thyroid Autoimmunity Affected by Recurrent Miscarriage

Impaired thyroid hormone availability during early pregnancy is associated with recurrent miscarriage (RM) and adverse pregnancy outcomes. The main cause of thyroid dysfunction is thyroid-related autoimmunity (TAI), characterized by a significantly higher serum level of thyroid-stimulating hormone (TSH) compared to that of women without thyroid autoimmunity. TAI is associated with a significantly increased risk of miscarriage, and the incidence of TAI in women experiencing RM is higher compared to normal fertile women. In the present study, we have performed a retrospective analysis comparing the ability to conceive, the number of miscarriages and full-term pregnancies between 227 euthyroid women with autoimmune thyroid disease affected by RM and treated with levothyroxine (LT4) as adjuvant therapy, and a control group of 230 untreated women. We have observed a significant improvement of full-term pregnancies in treated women (59%) compared to untreated women (13%, p < 0.0001). Compared to the control group, treated women had a lower percentage of miscarriages (12% vs. 30%) and improved capacity to conceive (57% vs. 29%). Using age as a variable, the outcome in women younger than 35 years was not influenced by the LT4 therapy. Whereas, in women over 35 years, supplementation with LT4 significantly reduced the miscarriage rate (p < 0.05). We can conclude that a transient impairment of TH availability, not easily detectable before pregnancy, could be an important cause of RM in a subset of euthyroid women with autoimmune thyroid disease. This transient impairment may be reverted using adjuvant treatment with low doses of LT4.

Impact of pregnancy on papillary thyroid carcinoma prognosis

Introduction

thyroid carcinoma is more frequent in women of reproductive age. It can affect both fertility and the course of pregnancy. The aim of the study was to investigate the influence of pregnancy as a factor of recurrence or progression, on the prognosis of thyroid carcinoma.

Methods

we conducted a retrospective cohort study of 117 young female patients followed up for papillary thyroid carcinoma (PTC) at the Department of Endocrinology, Diabetology and Metabolic Diseases of Ibn Rochd University Hospital of Casablanca, from January 2010 to December 2018, divided into 2 groups: group 1 composed of pregnant patients (n=42) and group 2 being the control group (n=75). Statistical analysis was made using SPSS software version 22.0.0.

Results

average age of pregnant patients was 35 ± 6.5 years old. Mean duration between first pregnancy and treatment completion was 4.4 ± 3.1 years. Over an average treatment duration of 14.4 months in postpartum, 30 patients were in remission (thyroglobulin (Tg) <1μg/l, negative thyroglobulin antibody and no morphological abnormality), while 12 had persistent symptoms (detectable Tg/thyroglobulin antibody and/or morphological abnormality). Thyroid stimulating hormone (TSH) during pregnancy was on average 0.83 mIU/l. Cancer progression was correlated with persistence of thyroid cancer to treatment before pregnancy (p = 0.01), pre-existing distant or locoregional metastases (p = 0.02) and delayed administration of radio-iodine therapy (p = 0.01). Interval between diagnosis and pregnancy, TSH level during pregnancy or the pre-conception thyroglobulin level did not have a statistically significant impact. Pregnancy was not associated with progression or recurrence of thyroid cancer (adjusted risk ratio 1.04, 95% confidence interval 0.91-1.32).

Conclusion

this study shows that pregnancy has no impact on recurrence or progression of thyroid cancer in patients declared in remission prior to conception.

Thyroid nodules and cancer during pregnancy, post-partum and preconception planning: Addressing the uncertainties and challenges

Thyroid nodules and thyroid cancer have become increasingly common worldwide. When discovered during pregnancy, they pose unique diagnostic and therapeutic challenges for both the treating physician and the patient. The benefits of treatment should be carefully weighed against risks that may adversely impact maternal and fetal health. In this review, we present current knowledge and controversies surrounding the management of thyroid nodules and thyroid cancer in pregnancy, in the post-partum period and during preconception planning.

Iodine deficiency in pregnancy: Still a health issue for the women of Cassino city, Italy

OBJECTIVE

The World Health Organization, the United Nations Children's Fund, and the International Council for the Control of Iodine Deficiency Disorders recommend a median urinary iodine concentration (UIC) in pregnant women between 150 µg/L and 249 µg/L. In the present study, we evaluated whether in the urban area of Cassino (central Italy), after a national salt iodination program (30 mg/kg) was introduced in 2005, the increased demand of iodine during pregnancy was satisfied.

METHODS

Between January 2016 and April 2017, 99 pregnant women were enrolled to evaluate UIC in spot urine samples, serum level of thyrotropin, free thyroxine, antithyroglobulin and antithyroperoxidase autoantibodies, and thyroid volume by ultrasonography. Eighty clinically healthy non-pregnant women were evaluated as controls.

RESULTS

The median UIC was of 97.7 µg/L and 110.3 µg/L, respectively, in control and pregnant women. A significant increase (P < 0.001) of median thyroid volume was found in pregnant women, relative to control women, being, respectively, 10.4 mL (range 3.68-19.49 mL) and 7.16 mL (range 2.57-14.00 mL). A positive correlation was found between thyroid volume and anthropometric parameters, and an inverse correlation was identified between free thyroxine serum levels and anthropometric parameters.

CONCLUSIONS

This observational study found that the majority of pregnant women and their fetuses appear not to be protected from the detrimental consequences of iodine deficiency. Therefore, the identification of new strategies to increase the knowledge and awareness of the general population regarding the beneficial effects of iodine supplementation during pregnancy is highly required.

Expression of Thyroid Hormone Receptors in Villous Trophoblasts and Decidual Tissue at Protein and mRNA Levels Is Downregulated in Spontaneous and Recurrent Miscarriages

Thyroid hormones are essential for the maintenance of pregnancy, and a deficiency in maternal thyroid hormones has been associated with early pregnancy losses. The expression of THRα1, THRβ1 and THRα2 increases with gestational age. The aim of this study was the investigation of the protein and mRNA-levels of THR isoforms THRα1, THRα2, THRβ1 and THRβ2 in normal, spontaneous and recurrent miscarriages. The identification of THR-expressing cells in the decidua was done with double immunofluorescence. The nuclear expression of THRα1, THRα2, THRβ1 and THRβ2 is downregulated at protein level in spontaneous and recurrent miscarriages in villous trophoblast tissue. In decidual tissue, we found a significant downregulation only for THRα1 in spontaneous miscarriages. For recurrent miscarriages, THRα1 and THRβ1 were both significantly downregulated in decidual tissue. By applying HLA-G as a trophoblast marker, we found a significant co-expression only for THRβ2. The results of our study show that thyroid hormone receptors THRα1, THRα2, THRβ1 and THRβ2 are downregulated in spontaneous and recurrent miscarriages. The majority of cells expressing the thyroid hormone receptors in the decidua are decidual stromal cells.

Management of thyroid peroxidase antibody euthyroid women in pregnancy: comparison of the american thyroid association and the endocrine society guidelines

The presence of thyroid autoantibodies is relatively high in women of childbearing age. There is evidence that positive thyroperoxidase antibody even in euthyroid women may increase the risk of spontaneous and recurrent pregnancy loss and preterm delivery. However, the evidence is not enough to justify recommendation on the screening of pregnant women for thyroid autoantibodies or LT4 supplementation for reducing maternal or fetal complications. In this paper we reviewed the related evidence and compared the new guidelines of the American Thyroid Association and Endocrine Society with respect to the screening and management of positive thyroperoxidase antibody in euthyroid pregnant women. As there was no major contradiction or disagreement between the two guidelines, either one of two guidelines may be used by clinicians for the appropriate management of thyroid autoimmunity during pregnancy.

Upstream adverse effects in risk assessment: a model of polychlorinated biphenyls, thyroid hormone disruption and neurological outcomes in humans

BACKGROUND

Increasing data on early biological changes from chemical exposures requires new interpretation tools to support decision-making.

OBJECTIVES

To test the possibility of applying a quantitative approach using human data linking chemical exposures and upstream biological perturbations to overt downstream outcomes.

METHODS

Using polychlorinated biphenyl (PCB) exposures and maternal thyroid hormone (TH) perturbations as a case study, we model three relationships: (1) prenatal PCB exposures and TH changes, using free T(4) (FT(4)); (2) prenatal TH and childhood neurodevelopmental outcomes; and (3) prenatal PCB exposures and childhood neurodevelopmental outcomes (IQ). We surveyed the epidemiological literature; extracted relevant quantitative data; and developed models for each relationship, applying meta-analysis where appropriate.

RESULTS

For relationship 1, a meta-analysis of 3 studies gives a coefficient of -0.27 pg/mL FT(4) per ln(sum of PCBs) (95% confidence interval [CI] -0.82 to 0.27). For relationship 2, regression coefficients from three studies of maternal FT(4) levels and cognitive scores ranged between 0.99 IQ points/(pg/mL FT(4)) (95% CI -0.31 to 2.2) and 7.6 points/(pg/mL FT(4)) (95% CI 1.2 to 16.3). For relationship 3, a meta-analysis of five studies produces a coefficient of -1.98 IQ points (95% CI -4.46 to 0.50) per unit increase in ln(sum of PCBs). Combining relationships 1 and 2 yields an estimate of -2.0 to -0.27 points of IQ per unit increase in ln(sum of PCBs).

CONCLUSIONS

Combining analysis of chemical exposures and early biological perturbations (PCBs and FT(4)) with analysis of early biological perturbations and downstream overt effects (FT(4) and IQ) yields estimates within the range of studies of exposures and overt effects (PCBs and IQ). This is an example approach using upstream biological perturbations for effect prediction.

Pregnant French women living in the Lyon area are iodine deficient and have elevated serum thyroglobulin concentrations

BACKGROUND

Iodine deficiency (ID) remains common in Europe, and may be especially detrimental during pregnancy. The aim of our study was to assess iodine status and thyroid function in healthy pregnant women in the Lyon metropolitan area.

METHODS

In a cross-sectional study, healthy pregnant women (n=228) with no history of thyroid disease were consecutively recruited from an obstetric clinic during all trimesters. Thyrotropin (TSH), free thyroxine (FT4), anti-thyroid peroxidase (anti-TPO) antibodies, thyroglobulin (Tg), and urinary iodine concentration (UIC) (n=100) were measured. Thyroid functions were compared with those in a control group of nonpregnant adults.

RESULTS

The median (range) UIC was 81 (8-832) μg/L, and 77% of pregnant women had a UIC <150 μg/L, indicating inadequate iodine intake. Overall, 11% of women had abnormal TSH or anti-TPO. The median FT4 (pmol/L) was 14.9, 12.6, and 11.5 in the first, second, and third trimesters, respectively. The median Tg in pregnant women was 16.2 μg/L, did not differ across trimesters, and was significantly higher than in the control group of nonpregnant adults (11.7 μg/L) (p=0.02). Controlling for maternal age and week of gestation, UIC was not a significant predictor of any of the thyroid function tests.

CONCLUSIONS

Pregnant women in the Lyon area are iodine deficient and have increased serum Tg concentrations compared with nonpregnant controls, likely due to physiological thyroid hyperstimulation during gestation exacerbated by ID.

Periconceptional changes in thyroid function: a longitudinal study

BACKGROUND

Limitations in our current knowledge of normative physiologic changes in thyroid function during the periconception window narrow our ability to establish an optimal approach to screening and diagnosis of thyroid disease in pregnant women. The objective of this study was to characterize changes in thyroid function during the transition from the pre-pregnant to pregnant state in normal fertile women.

METHODS

Women (N = 60) ages 30-42 years without a history of thyroid disease, who were planning pregnancy, were observed prospectively before and during early pregnancy. Thyroid function (thyroid stimulating hormone, TSH and free thyroxine, FT4) was measured before conception and between 6 and 9 weeks gestation. Pre-pregnancy samples were analyzed for thyroid antibodies. Bivariate analyses and longitudinal curves (general estimating equation models) were used to analyze changes in thyroid function during the periconception window by antibody status.

RESULTS

Pre-pregnancy TSH values were significantly higher than early pregnancy TSH (p < 0.001), but FT4 values did not differ (p = 0.53). TSH declined as gestational age increased (P < 0.01). Thyroid antibody positive women had a higher pre-pregnancy TSH compared to antibody negative women (p < 0.01). Periconceptional change in thyroid function was more variable among women with antibodies (p < 0.001). 50% of women with elevated pre-pregnancy TSH values (TSH > 3.0 mIU/L) had normal TSH values (TSH < 2.5 mIU/L) in pregnancy.

CONCLUSIONS

TSH values decline during the transition from pre-pregnancy to early pregnancy. The change in TSH appears to be less predictable in women with thyroid antibodies. Periconceptional changes in thyroid function should be considered in formulating prenatal thyroid screening guidelines.

Polybrominated diphenyl ethers, hydroxylated polybrominated diphenyl ethers, and measures of thyroid function in second trimester pregnant women in California

Prenatal exposure to polybrominated diphenyl ethers (PBDEs) may disrupt thyroid function and contribute to adverse neurodevelopmental outcomes. We conducted a pilot study to explore the relationship between serum concentrations of lower-brominated PBDEs (BDE-17 to -154), higher-brominated PBDEs (BDE-183 to -209), and hydroxylated PBDE metabolites (OH-PBDEs) with measures of thyroid function in pregnant women. Concentrations of PBDEs, OH-PBDEs, thyroid-stimulating hormone (TSH), total thyroxine (T(4)), and free T(4) were measured in serum samples collected between 2008 and 2009 from 25 second trimester pregnant women in California. Median concentrations of lower-brominated PBDEs and OH-PBDEs were the highest reported to date in pregnant women. Median concentrations of BDE-47 and the sum of lower-brominated PBDEs (ΣPBDE(5)) were 43.1 ng/g lipid and 85.8 ng/g lipid, respectively, and the sum of OH-PBDEs (ΣOH-PBDE(4)) was 0.084 ng/mL. We observed a positive association between the weighted sum of chemicals known to bind to transthyretin (ΣTTR binders) and TSH levels. We also found positive associations between TSH and ΣPBDE(5), ΣOH-PBDE(4), BDE-47, BDE-85, 5-OH-BDE47, and 4'-OH-BDE49, and an inverse association with BDE-207. Relationships with free and total T(4) were weak and inconsistent. Our results indicate that PBDE exposures are elevated in pregnant women in California and suggest a relationship with thyroid function. Further investigation is warranted to characterize the risks of PBDE exposures during pregnancy.

Levothyroxine treatment in pregnancy: indications, efficacy, and therapeutic regimen

The prevalence of overt and subclinical hypothyroidism during pregnancy is estimated to be 0.3–0.5% and 2–3%, respectively. Thyroid autoantibodies are found in 5–18% of women in the childbearing age. The aim of this review is to underscore the clinical significance of these findings on the health of both the mother and her offspring. Methods of evaluation of thyroid function tests (TFTs) during pregnancy are described as are the threshold values for the diagnosis of overt and subclinical hypothyroidism or hypothyroxinemia. Anticipated differences in TFTs in iodine-sufficient and iodine-deficient areas are discussed and data are provided on potential complications of hypothyroidism/hypothyroxinemia and autoimmune thyroid disease during pregnancy and adverse effects for the offspring. The beneficial effects of levothyroxine therapy on pregnancy outcomes and offspring development are discussed with a proposed treatment regimen and follow up strategy.

Thyroid function at the third trimester of pregnancy in a Northern French population

OBJECTIVES

During pregnancy, the production rate of thyroid hormone increases when iodine intake is sufficient. However, the appropriateness of the free thyroxin (FT4) immunoassay is questionable. We have therefore evaluated prospectively the thyroid function in pregnancy and the relevance of the FT4 immunoassay.

PATIENTS AND METHODS

The thyroid function of 114 pregnant, healthy Parisian women with mild iodine deficiency was studied at the third trimester of pregnancy, 55 of whom served as their own control three months after delivery, and the results were compared to North American reference values.

RESULTS

All French pregnant women showed an increase in thyroxin binding globulin (TBG) serum levels. FT4 levels decreased by about 30% at the third trimester of pregnancy, as compared to 10-15% in the American population. Moreover, the increase in total thyroxin (TT4) secretion represented only 27%, as compared to 50% in the American population. Linear regression model analysis showed a positive correlation between levels of TT4 and TBG, TT4 and FT4, as well as FT4 and free thyroxin index (FTI).

CONCLUSION

The hypothyroxinemia at the third trimester of pregnancy was more prominent in the Parisian population and insufficient iodine intake could be responsible for the deficient increase in TT4. It is therefore concluded that the inability of the thyroid to establish the required equilibrium could be corrected by systematic iodine supplementation before pregnancy. Finally, the strong correlation between FT4 and FTI suggests that the quality of FT4 test immunoassay is appropriate for estimating FT4 serum levels during pregnancy.

Impact of pregnancy on outcome and prognosis of survivors of papillary thyroid cancer

BACKGROUND

Papillary thyroid cancer (PTC) commonly affects women of child-bearing age. During normal pregnancy, several factors may have a stimulatory effect on normal and nodular thyroid growth. The aim of the study was to determine whether pregnancy in thyroid-cancer survivors poses a risk of progression or recurrence of the disease.

METHODS

The files of 63 consecutive women who were followed at the Endocrine Institute for PTC in 1992-2009 and had given birth at least once after receiving treatment were reviewed for clinical, biochemical, and imaging data. Thyroglobulin levels and neck ultrasound findings were compared before and after pregnancy. Demographic and disease-related characteristics and levels of thyroid-stimulating hormone (TSH) during pregnancy were correlated with disease persistence before conception and disease progression during pregnancy using Pearson's analysis.

RESULTS

Mean time to the first delivery after completion of thyroid-cancer treatment was 5.08 ± 4.39 years; mean duration of follow up after the first delivery was 4.84 ± 3.80 years. Twenty-three women had more than one pregnancy, for a total of 90 births. Six women had evidence of thyroid cancer progression during the first pregnancy; one of them also showed disease progression during a second pregnancy. Another two patients had evidence of disease progression only during their second pregnancy. Mean TSH level during pregnancy was 2.65 ± 4.14 mIU/L. There was no correlation of disease progression during pregnancy with pathological staging, interval from diagnosis to pregnancy, TSH level during pregnancy, or thyroglobulin level before conception. There was a positive correlation of cancer progression with persistence of thyroid cancer before pregnancy and before total I-131 dose was administered.

CONCLUSIONS

Pregnancy does not cause thyroid cancer recurrence in PTC survivors who have no structural or biochemical evidence of disease persistence at the time of conception. However, in the presence of such evidence, disease progression may occur during pregnancy, yet not necessarily as a consequence of pregnancy. The finding that a nonsuppressed TSH level during pregnancy does not stimulate disease progression suggests that it may be an acceptable therapeutic goal in this setting.

Subclinical thyroid disorders: significance and clinical impact

Subclinical thyroid diseases are defined by abnormal serum thyroid stimulating hormone (TSH) levels associated with normal thyroid hormone concentrations. The diagnosis of these conditions depends on defining the 'normal' euthyroid TSH range; in this review, arguments for and against lowering the upper limit of TSH are summarised. Although, subclinical hypothyroidism and subclinical hyperthyroidism are frequently encountered, their long-term consequences are debated due to conflicting results from many observational studies. The causes, effects and outcomes of treatment of both subclinical diseases are described, and the direction of future research in these conditions is outlined.

Maternal thyroid function during gestation is related to breech presentation at term

OBJECTIVE

To study the relationship between suboptimal maternal thyroid function during gestation and breech presentation at term.

DESIGN

Prospective follow-up study during three trimesters of gestation.

PATIENTS

A total of 1058 Dutch Caucasian healthy pregnant women were prospectively followed from 12 weeks gestation until term (>or=37 weeks) delivery.

MEASUREMENTS

Maternal thyroid parameters [TSH, free T4 (FT4) and auto-antibodies to thyroid peroxidase] were assessed at 12, 24 and 36 weeks gestation as well as foetal presentation at term.

RESULTS

At term, 58 women (5.5%) presented in breech. Compared with women with foetuses in the cephalic position, those women who presented in breech at term had significantly higher TSH concentrations, but only at 36 weeks gestation (P = 0.007). No between group differences were obtained for FT4 level at any assessment. The prevalence of breech presentation in the subgroup of women with TSH >or= 2.5 mIU/l (90th percentile) at 36 weeks gestation was 11%, compared with 4.8% in the women with TSH < 2.50 mIU/l (P = 0.006). Women with TSH below the 5th percentile had no breech presentations. Breech position was significantly and independently related to high maternal TSH concentration (>or=2.5 mIU/l) at 36 weeks gestation (O.R.: 2.23, 95% CI: 1.14-4.39), but not at 12 and 24 weeks gestation.

CONCLUSIONS

Women with TSH levels above 2.5 mIU/l during end gestation are at risk for breech presentation, and as such for obstetric complications.

Graves hyperthyroidism and pregnancy: a clinical update

OBJECTIVE

To provide a clinical update on Graves' hyperthyroidism and pregnancy with a focus on treatment with antithyroid drugs.

METHODS

We searched the English-language literature for studies published between 1929 and 2009 related to management of hyperthyroidism in pregnancy. In this review, we discuss differential diagnosis of hyperthyroidism, management, importance of early diagnosis, and importance of achieving proper control to avoid maternal and fetal complications.

RESULTS

Diagnosing hyperthyroidism during pregnancy can be challenging because many of the signs and symptoms are similar to normal physiologic changes that occur in pregnancy. Patients with Graves disease require prompt treatment with antithyroid drugs and should undergo frequent monitoring for signs of fetal and maternal hyperthyroidism and hypothyroidism. Rates of maternal and perinatal complications are directly related to control of hyperthyroidism in the mother. Thyroid receptor antibodies should be assessed in all women with hyperthyroidism to help predict and reduce the risk of fetal or neonatal hyperthyroidism or hypothyroidism. The maternal thyroxine level should be kept in the upper third of the reference range or just above normal, using the lowest possible antithyroid drug dosage. Hyperthyroidism may recur in the postpartum period as Graves disease or postpartum thyroiditis; thus, it is prudent to evaluate thyroid function 6 weeks after delivery. Preconception counseling, a multidisciplinary approach to care, and patient education regarding potential maternal and fetal complications that can occur with different types of treatment are important.

CONCLUSION

Preconception counseling and a multifaceted approach to care by the endocrinologist and the obstetric team are imperative for a successful pregnancy in women with Graves hyperthyroidism.

Autoimmune thyroid disease in pregnancy: a review

The maternal physiological changes that occur in normal pregnancy induce complex endocrine and immune responses. During a normal pregnancy, thyroid gland volume may enlarge, and thyroid hormone production increases. Hence, the interpretation of thyroid function during gestation needs to be adjusted according to pregnancy-specific ranges. The elevated prevalence of gestation-related thyroid disorders (10%-15%) and the important repercussions for both mother and fetus reported in multiple studies throughout the world denote, in our opinion, the necessity for routine thyroid function screening both before and during pregnancy. Once thyroid dysfunction is suspected or confirmed, management of the thyroid disorder necessitates regular monitoring in order to ensure a successful outcome. The aim of treating hyperthyroidism in pregnancy with antithyroid drugs is to maintain serum thyroxine (T(4)) in the upper normal range of the assay used with the lowest possible dose of drug, whereas in hypothyroidism, the goal is to return serum thyroid-stimulating hormone (TSH) to the range between 0.5 and 2.5 mU/L.

Adjustment of L-T4 substitutive therapy in pregnant women with subclinical, overt or post-ablative hypothyroidism

OBJECTIVE

Maternal hyperthyrotropinaemia is associated with an increased risk of adverse maternal and neonatal outcomes. Physiological changes during pregnancy require an increased production of thyroid hormones (or an increase in daily substitutive doses of L-T4 in hypothyroid patients) to meet the maternal and foetal needs. The aim of the study was to evaluate variations of substitutive L-T4 doses that are able to maintain serum TSH between 0.5 and 2.5 mU/l in pregnant women with subclinical- (SH), overt- (OH) and post-ablative (PH) hypothyroidism.

DESIGN

This was a retrospective study on hypothyroid pregnant women referred to the out-patient department between January 2004 and December 2006.

PATIENTS AND MEASUREMENTS

A total of 185 pregnant women were studied during gestation; 155 patients (76 SH, 52 OH, 27 PH) were already on L-T4 before conception and 30 (SH) started L-T4 therapy during gestation. Thyroid function and body weight were evaluated every 4-6 weeks.

RESULTS

In the group of patients already treated before conception, 134 (86.5%) increased L-T4 doses during gestation one or more times, eight (6%) reached a definitive therapeutic dosage within the 12th week of pregnancy, 64 (47.8%) within the 20th week and 62 (46.2%) within the 31st week. This initial L-T4 increase at the first evaluation during pregnancy was 22.9 +/- 9.8 microg/day. The final L-T4 doses were significantly different depending on the aetiology, being 101.0 +/- 24.6 microg/day in SH, 136.8 +/- 30.4 microg/day in OH and 159.0 +/- 24.6 microg/day in PH. The per cent increase of L-T4, expressed as Delta% of absolute dose, was +70% in SH, +45% in OH and +49% in PH as compared to baseline dose. In SH patients diagnosed during gestation, the starting L-T4 dose was higher than L-T4 dose before pregnancy of SH patients already treated (75.4 +/- 14.5 and 63.2 +/- 20.1 microg/day, respectively), whereas the final doses were similar. L-T4 dose was increased one or more times in 24 patients (80%), 8 reached the definitive dosage within the second trimester (33.3%) and 16 within the third trimester (66.7%).

CONCLUSIONS

Serum TSH and FT4 measurements are mandatory in pregnant patients and the optimal timing for increasing L-T4 is the first trimester of pregnancy, though many patients require adjustments also during the second and third trimester. The aetiology of hypothyroidism influences the adjustment of L-T4 therapy and SH patients needed a larger increase than OH and PH. Close monitoring during pregnancy appears to be mandatory in hypothyroid women.

Extended hyperemesis gravidarum in a patient after total thyroidectomy

INTRODUCTION

Human chorionic gonadotropin is regarded as, at least, one of the main factors responsible for hyperemesis gravidarum by direct stimulation of the thyroid gland on the basis of a close homology to the structure of TSH. However, questions to this theory of hCG-induced gestational hyperthyroidism still remain.

CASE REPORT

We present for the first time a rare case of hyperemesis gravidarum in a patient with a previous removed thyroid gland and an adequate thyroxin replacement. In this case report we present an extended hyperemesis gravidarum in a patient after total thyroidectomy and thus artificially well-set thyroid parameters.

CONCLUSION

Although transient hyperthyroidism is widely thought to be causative of a hyperemesis during pregnancy, this case report with a mildly hypothyroidism emphasizes that there might be other, yet unknown, factors that can cause such a severe complication.

First- and second-trimester thyroid hormone reference data in pregnant women: a FaSTER (First- and Second-Trimester Evaluation of Risk for aneuploidy) Research Consortium study

OBJECTIVE

The purpose of this study was to calculate first and second trimester reference ranges and within-woman correlations for TSH, free T4, and thyroid antibodies.

STUDY DESIGN

TSH, free T4, and thyroid antibodies were measured in paired sera from 9562 women in the FaSTER trial of Down syndrome screening.

RESULTS

The median first trimester TSH (1.05 mIU/L) is lower than the second (1.23 mIU/L); and 98th centile is higher (4.15 vs 3.77 mIU/L). Within-woman paired TSH correlations are moderately strong (r(2) = 0.64). Among women with first trimester TSH values above the 98th centile, second trimester values are over the 95th centile in 68%. Median first trimester free T4 values (1.10 ng/dL) are higher than second (1.01 ng/dL). Paired free T4 measurements correlate weakly (r(2) = 0.23). Among women with first trimester free T4 values below the 2nd centile, second trimester values are below the 5th centile in 32%. Antibody measurements correlate strongly between trimesters (thyroperoxidase r(2) = 0.79, thyroglobulin r(2) = 0.83).

CONCLUSION

TSH and free T4 measurements require gestation-specific reference ranges.

Association of first-trimester thyroid function test values with thyroperoxidase antibody status, smoking, and multivitamin use

OBJECTIVE

To determine first-trimester thyroid function values and associations with thyroperoxidase antibody (TPO-Ab) status, smoking, emesis, and iodine-containing multivitamin use.

METHODS

We collected information by interview, questionnaire, and blood draw at the initial obstetric visit in 668 pregnant women without known thyroid disease. We compared thyroid-stimulating hormone (TSH), total thyroxine (T4), and free T4 index (FT4I) values by TPO-Ab status. Multiple regression was used to identify characteristics associated with thyroid function values.

RESULTS

The following median (range containing 95% of the data points) thyroid function test values were obtained in 585 TPO-Ab-negative women: TSH, 1.1 mIU/L (0.04-3.6); FT4I, 2.1 (1.5-2.9); and T4, 9.9 microg/dL (7.0-14.0). The following median (range containing 95% of the data points) thyroid function test values were obtained in 83 TPO-Ab-positive women: TSH, 1.8 mIU/L (0.3-6.4) (P<.001); FT4I, 2.0 (1.4-2.7) (P = .06); and T4, 9.3 microg/dL (6.8-13.0) (P = .03) (P values denote statistically significant differences between TPO-Ab-positive and negative participants). Among TPO-Ab-negative participants, TSH level was not associated with use of iodine-containing multivitamins, smoking, or race. TSH increased 0.03 mIU/L for every year of maternal age (P = .03) and decreased by 0.3 mIU/L for every increase in parity (P<.001). T4 decreased 0.04 microg/dL for every year of maternal age (P = .04). Mean FT4I was 2.05 in smokers and 2.20 in nonsmokers (P<.01). There were no relationships between T4 or FT4I and parity, race, or iodine-containing multivitamin use.

CONCLUSION

TPO-Ab status of pregnant women should be considered when constructing trimester-specific reference ranges because elevated serum TPO-Ab levels are associated with higher TSH and lower T4 values.

The clinical significance of subclinical thyroid dysfunction

Subclinical thyroid disease (SCTD) is defined as serum free T(4) and free T(3) levels within their respective reference ranges in the presence of abnormal serum TSH levels. SCTD is being diagnosed more frequently in clinical practice in young and middle-aged people as well as in the elderly. However, the clinical significance of subclinical thyroid dysfunction is much debated. Subclinical hyper- and hypothyroidism can have repercussions on the cardiovascular system and bone, as well as on other organs and systems. However, the treatment and management of SCTD and population screening are controversial despite the potential risk of progression to overt disease, and there is no consensus on the thyroid hormone and thyrotropin cutoff values at which treatment should be contemplated. Opinions differ regarding tissue effects, symptoms, signs, and cardiovascular risk. Here, we critically review the data on the prevalence and progression of SCTD, its tissue effects, and its prognostic implications. We also examine the mechanisms underlying tissue alterations in SCTD and the effects of replacement therapy on progression and tissue parameters. Lastly, we address the issue of the need to treat slight thyroid hormone deficiency or excess in relation to the patient's age.

The prevalence of iodine deficiency in women of reproductive age in the United States of America

Objective: To review the iodine status of women as assessed through National Health and Nutrition Examination Surveys from 1971 to 2002.

Design and Setting: National normative estimates of iodine status of the civilian, non-institutionalized population in the United States of America.

Subjects: Women of reproductive age and pregnant women.

Results: In the United States of America, iodine began to be added to the diet in the 1920s. An excessive iodine intake was documented by the first National Health and Nutrition Examination Survey (NHANES I) in the 1970s which reported a median urinary iodine (UI) concentration of 320 μg l-1. In the NHANES III survey, conducted between 1988 and 1994, the median UI concentration had decreased to 145 μg l-1, while 14.9% of women aged 15-44 years and 6.9% of pregnant women had a UI concentration 50 μg l-1. The concentrations of serum T4 and thyroid-stimulating hormone of women with a low UI concentration did not, however, indicate an iodine deficiency.

Conclusions: Further studies of the association between iodine excretion and biochemical and physiological changes should be undertaken to better understand women's needs for iodine and to develop criteria to monitor them in pregnancy. Because of the potential harm caused by iodine deficiency during pregnancy, we support the use of iodine supplements for all pregnancies while these data are being collected.

Hypothyroidism

Hypothyroidism is one of the most common disorders encountered in an endocrine office practice. This article reviews the epidemiology, etiology, clinical presentation, diagnosis, and treatment of hypothyroidism. We emphasize some of the more recent issues, such as combination thyroid hormone therapy, management of hypothyroidism during pregnancy, and the management of subclinical hypothyroidism.

Maternal thyroid disease as a risk factor for craniosynostosis

OBJECTIVE

To study the relationship between maternal thyroid disease and craniosynostosis using data from the National Birth Defects Prevention Study, a multisite, case-control study.

METHODS

Case infants (n=431) were identified through population-based birth defects surveillance systems at eight sites and had craniosynostosis verified by radiographic imaging. Control infants (n=4,094) consisted of a random sample of live births with no major birth defects from the same population as the case infants. Information on thyroid disease was based on self-report: mothers who reported either a thyroid disorder or use of a medication to treat a thyroid disorder during pregnancy were considered to have thyroid disease. Using an unconditional logistic regression model, we considered potential confounding factors (maternal age, race or ethnicity, smoking, body mass index, preexisting diabetes, plurality, gravidity, family history, infant sex).

RESULTS

Among case mothers, 19 (4.4%) were classified as having thyroid disease, compared with 65 (1.6%) of control mothers. Maternal thyroid disease was associated with craniosynostosis after controlling for maternal age (adjusted odds ratio 2.47, 95% confidence interval 1.46-4.18), the only factor that remained significant in the final model.

CONCLUSION

These data provide additional evidence that maternal thyroid disease (most likely Graves' disease) or its treatment is associated with craniosynostosis. Given the frequency of maternal thyroid disease, this association warrants further investigation.

LEVEL OF EVIDENCE

II.

The effect of infertility medication on thyroid function in hypothyroid women who conceive

OBJECTIVE

To determine whether infertility medications alter thyroid status in patients with treated hypothyroidism, and whether resulting pregnancies require additional thyroid supplementation compared with those conceived spontaneously.

DESIGN

Prospective observational study of 18 infertility patients with treated hypothyroidism who conceived between July 2005 and July 2006 with or without infertility medications. Thyroid studies were performed prior to conception, at the time of pregnancy diagnosis, and approximately 6 weeks after an increase in thyroid replacement dose.

MAIN OUTCOME

Orally medicated conceptions were similar to spontaneous conceptions on all thyroid related variables, and therefore the two groups were combined for analysis. Although there was a nonsignificant difference in thyrotropin (TSH) levels postconception (3.8 mIU/L vs. 2.2 mIU/L, p = 0.30), there was no difference in TSH levels after increase in thyroid replacement dose (1.7 mIU/L vs. 1.1 mIU/L, p = 0.30) between patients who conceived after gonadotropin stimulation compared with those who conceived spontaneously or with oral medications. The mean percent dose increases for the nongonadotropin and gonadotropin pregnancy groups were 30.6% and 32.4%, respectively.

CONCLUSIONS

Hypothyroid patients who conceive after gonadotropin stimulation or with oral medications for ovulation induction do not need additional thyroid supplementation compared with those who conceive spontaneously.

Impact of pregnancy on serum thyroglobulin and detection of recurrent disease shortly after delivery in thyroid cancer survivors

OBJECTIVE

Since pregnancy can stimulate thyroid growth, we examined the effect of pregnancy on recurrence and serum thyroglobulin (Tg) shortly after delivery in thyroid cancer survivors.

DESIGN

Retrospective analysis of thyroid cancer survivors who became pregnant after completing initial therapy.

MAIN OUTCOME

36 women (age 34 +/- 4 years) who became pregnant a median of 4.3 years after initial therapy for differentiated thyroid cancer were evaluated a median of 4 months after delivery. As part of their initial therapy, 23 women underwent total thyroidectomy with radioactive iodine remnant ablation (RRA), six had total thyroidectomy without RRA, and seven underwent lobectomy without RRA. Following total thyroidectomy with or without RRA, no evidence of recurrence was detected in the early postpartum period in women with negative prepregnancy ultrasound and either undetectable or low suppressed Tg levels. However, disease progression was documented as enlargement of a previously stable cervical lymph node in one of three patients and a marked rise in serum Tg without evidence of structural disease progression in a patient with previously stable distant metastases. When analyzed based on initial therapy, the mean suppressed Tg after delivery was not significantly different than the prepartum value. However, eight women had Tg values after delivery more than 20% higher than the baseline Tg before pregnancy (three with known disease, five with no clinical evidence of disease).

CONCLUSION

In thyroid cancer survivors, pregnancy is unlikely to cause clinically significant disease recurrence in the early postpartum period when structural imaging studies confirm the absence of residual disease but can occasionally be associated with progression of known metastatic lesions. Even though the serum Tg did not differ significantly before and after pregnancy, the long-term implications of minor rise in serum Tg seen in some individual patients cannot be assessed without longer studies in larger cohorts.

Thyroid medications during pregnancy

Euthyroid women experience dramatic changes in their thyroid physiology in order to accommodate the presence of placental and fetal tissues. These adaptations to the pregnant state make it crucial to develop reliable trimester-specific intervals for thyroid parameters. Use of non-pregnant reference intervals could lead to erroneous assessment of thyroid status in this rapidly changing hormonal environment. Only with a full appreciation of physiologic changes in thyroid parameters during a euthyroid pregnancy, can thyroid dysfunction be appropriately diagnosed and managed. Iodine sufficiency during pregnancy can be achieved with supplementation using a multivitamin. Both hypothyroidism and hyperthyroidism should be diagnosed using the appropriate reference intervals for pregnancy. Hypothyroid women are best treated with a specific brand of levothyroxine. Hypothyroidism should ideally be treated prior to conception. If newly recognized during pregnancy, it should be fully treated as early as possible. Frequent monitoring of thyroid status is essential as many women demonstrate an increased requirement for thyroid hormone during the first trimester. Although mild hyperthyroidism may be well tolerated during pregnancy, overt hyperthyroidism requires treatment. Thionamides are the mainstay of therapy. Following their initiation, close monitoring is required to avoid maternal and fetal hypothyroidism. There are occasional circumstances when other medical therapy or surgical therapy may be employed for hyperthyroidism. Thyroidectomy is generally safe in the second trimester in an appropriately prepared woman. There is limited data about the role and safety of oral contrast agents, iodine, amiodarone, and perchlorate. Radioiodine therapy is contradicted during pregnancy.

Iodine intake in pregnancy in Ireland — A cause for concern?

BACKGROUND

Adequate dietary iodine intake is necessary to maintain maternal thyroid function at a level permitting normal neuropsychological development of the foetus.

AIMS AND METHODS

To determine dietary iodine status by measuring urinary iodine excretion (UIE), proportional to dietary intake, in Irish mothers during the first trimester of pregnancy.

RESULTS

Median UIE showed seasonal variations, being lower in summer than in winter. The median values in pregnant women were, summer 45microg/l, winter 68microg/l. Equivalent values for controls were 43 and 91microg/l respectively. UIE required to achieve WHO recommended daily iodine intakes would be 120-180microg/l. In the Irish subjects UIE values suggestive of iodine deficiency (<50microg/l) were observed in 55% of pregnant women tested in summer and 23% in winter. Dairy milk iodine, a major dietary iodine source, showed similar variation.

CONCLUSIONS

While there is as yet no available evidence of widespread thyroid hypofunction in the Irish obstetric population, the findings are a cause of concern, which if confirmed by a more comprehensive investigation, may indicate the need for iodine prophylaxis.

Are women who are treated for hypothyroidism at risk for pregnancy complications?

OBJECTIVE

The purpose of this study was to investigate the outcomes that are associated with pregnancy and treated hypothyroidism.

STUDY DESIGN

This was a retrospective cohort study of all women who received prenatal care and were delivered at the University of California, San Francisco, between 1989 and 2001. All patients with hypothyroidism diagnosed before pregnancy or early in pregnancy were identified. Maternal, fetal, and obstetric outcomes were then collected and analyzed for women with hypothyroidism and compared with women without hypothyroidism.

RESULTS

Among 20,499 deliveries, there were 419 women (2.1%) who were treated for hypothyroidism during the study period. Hypothyroidism was more common among women > or =35 years old, white women, and women without Medicaid insurance. Treated hypothyroidism was not associated with any increase in maternal, fetal, or neonatal complications. In addition, hypothyroidism did not affect mode of delivery.

CONCLUSION

Compared with patients without hypothyroidism, patients with treated hypothyroidism are not at any increased risk for perinatal morbidity.