Hypothyroidism in pregnancy: pre-pregnancy thyroid status influences gestational thyroxine requirements

Levothyroxine dosages during pregnancy among hypothyroid women. An experience from a tertiary care center of Karachi, Pakistan, based on data from Maternal Hypothyroidism on Pregnancy Outcomes Study (MHPO-5)

Objectives

The dosage of levothyroxine (LT4) during pregnancy differs among different ethnic groups worldwide. These differences are due to variations in geographical iodine distribution, autoimmunity, and variations in thyrotropin (TSH) targets for pregnancy. To the best of our knowledge, we report the levothyroxine dosage prescribed during pregnancy in hypothyroid women, for the first time from Pakistan.

Results

Levothyroxine dosage of 280 hypothyroid women during pregnancy were reviewed. The median LT4 dosages prescribed before conception was 85.7 mcg per day which increased by 14.3 mcg per day in the first trimester (P 0.001). A significant difference in dosage was observed between controlled and uncontrolled TSH groups in the first trimester (P 0.05). Lower LT4 dosage was prescribed for subclinical hypothyroid women as compared to overt hypothyroid cases, whereas dosages did not differ according to autoimmune status in the latter part of gestation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13104-022-05984-7.

Preconception management of thyroid dysfunction

Uncorrected thyroid dysfunction in pregnancy has well-recognized deleterious effects on foetal and maternal health. The early gestation period is one of the critical foetal vulnerability during which maternal thyroid dysfunction may have lasting repercussions. Accordingly, a pragmatic preconception strategy is key for ensuring optimal thyroid disease outcomes in pregnancy. Preconception planning in women with hypothyroidism should pre-empt and mirror the adaptive changes in the thyroid gland by careful levothyroxine dose adjustments to ensure adequate foetal thyroid hormone delivery in pregnancy. In hyperthyroidism, the goal of preconception therapy is to control hyperthyroidism while curtailing the unwanted side effects of foetal and maternal exposure to antithyroid drugs. Thus, pregnancy should be deferred until a stable euthyroid state is achieved, and definitive therapy with radioiodine or surgery should be considered in women with Graves' disease planning future pregnancy. Women with active disease who are imminently trying to conceive should be switched to propylthiouracil either preconception or at conception in order to minimize the risk of birth defects from carbimazole or methimazole exposure. Optimal strategies for women with borderline states of thyroid dysfunction namely subclinical hypothyroidism, isolated hypothyroxinaemia and thyroid autoimmunity remain uncertain due to the dearth of controlled interventional trials. Future trial designs should aspire to recruit and initiate therapy before conception or as early as possible in pregnancy.

Levothyroxine liquid solution versus tablet form for replacement treatment in pregnant women

OBJECTIVE

To evaluate the need and the magnitude of levothyroxine (LT4) increase in hypothyroid pregnant women on liquid compared to tablet formulations.

METHODS

Patients were recruited by searching our "thyroid patients" database. The selection criteria were as follows: a) pregnant women on treatment for hypothyroidism (both liquid and tablet LT4) who gave birth at our hospital between February 2012 and January 2014; b) thyroid stimulating hormone (TSH) and free thyroxine (FT4) levels obtained at least 3 months before missed menstrual cycle, with a TSH value less than 2.5 mIU/L and c) TSH and FT4 obtained within 12 weeks of pregnancy, and each month subsequently.

RESULTS

During pregnancy, 8/31 (25.5%) of the women had to increase the dosage of LT4. Of these, 7/17 (41.2%) were on LT4 replacement therapy with tablets, and 1/14 (7.1%) with liquid formulation (p = 0.038). Daily LT4 was significantly increased in the liquid group only (52.9 ± 19.5 versus 67.5 ± 19.2 mcg/day (p = 0.013). A logistic regression analysis showed that the treatment with LT4 tablets was the only predictor of LT4 increase (OR: 0.44; 95% CI: 0.04-0.83; p = 0.031).

CONCLUSION

Pregnant women on optimal replacement therapy before pregnancy require an increase of LT4 dosage more often when on a tablet than liquid formulation.

Levothyroxine dose adjustment in hypothyroid women achieving pregnancy through IVF

OBJECTIVE

About one out of two women with primary hypothyroidism has to increase the dosage of exogenous levothyroxine (L-T4) during pregnancy. Considering the detrimental impact of IVF on thyroid function, it has been claimed but not demonstrated that L-T4 dose adjustment may be more significant in hypothyroid women who become pregnant after IVF.

DESIGN

Retrospective cohort study.

METHODS

Hypothyroid-treated women who achieved a live birth through IVF were reviewed. Women could be included if thyroid function was well compensated with L-T4 before the IVF cycle (i.e., serum TSH <2.5  mIU/l and serum free T4 within the normal range). Serum TSH and dose adjustment were evaluated at five time points during pregnancy. The trimester ranges for serum TSH considered as reference to adjust L-T4 therapy were 0.1-2.5  mIU/l for the first trimester, 0.2-3.0  mIU/l for the second trimester, and 0.3-3.0  mIU/l for the third trimester.

RESULTS

Thirty-eight women were selected. During the whole pregnancy 32 women (84%; 95% CI: 72-96%) required an increase in the dose of L-T4. In most cases (n=28), this occured within the first 5-7 weeks of gestation (74%, 95% CI: 58-85%). At 5-7 weeks of gestation, the median (interquartile range) increase of L-T4 dose for the whole cohort was 26% (0-50%). At 30-32 weeks, it was 33% (14-68%). In order to identify predictive factors of dose adjustment, we compared women who did (n=28) and did not (n=10) adjust L-T4 dosage at 5-7 weeks' gestation. Significant differences emerged for thyroid autoimmunity prevalence and for the distribution of hypothyroidism aetiology.

CONCLUSIONS

The vast majority of hypothyroid-treated women who achieve pregnancy through IVF need an increase in the L-T4 dose during gestation. This requirement tends to occur very early during gestation.

Levothyroxine Dosage Requirement During Pregnancy in Well-Controlled Hypothyroid Women: A Longitudinal Study

Background:

Untreated maternal hypothyroidism can have adverse effects on both the mother and fetus, but it can potentially be prevented by adequate levothyroxine replacement. This study was conducted to determine what percentage of hypothyroid pregnant women who were taking levothyroxine needed to adjust their medication dosage, and when and how much it should be increased.

Methods:

In this longitudinal study, 81 well-controlled hypothyroid women (TSH≤ 2.5 mIU/L) were monitored throughout pregnancy. Thyroid function tests were performed before conception, after the first missed menstrual period, in the second and third trimesters of pregnancy and one month after delivery. Levothyroxine dosage was adjusted according to TSH levels measured.

Results:

Of the 81 pregnancies studied, the pregnancy outcomes were 74 full-term births, six abortions and one pre-term birth. The levothyroxine dosage needed to be increased in 84% (CI95%= 74-90) of the pregnancies (OR=5.2, CI95%= 2.9-9.4). Most levothyroxine dose adjustments were made in the first trimester of gestation. The levothyroxine requirement increased 50% (CI95%= 41-59) in the first trimester, 55% (CI95%= 45-64) in the second trimester and 62% (CI95%= 52-72) in the third trimester. Levothyroxine dosage was decreased for 6 cases (7.4%), and no adjustment was made for 7 women (8.6%).

Conclusions:

Increases in levothyroxine dosage administered in pregnancy appear to be indispensible in the majority of patients with well-controlled hypothyroidism, especially in the first trimester. However, this change was not universal and levothyroxine dosage decreased in a few cases and remained unchanged in others.

Preconception care: screening and management of chronic disease and promoting psychological health

INTRODUCTION

A large proportion of women around the world suffer from chronic diseases including mental health diseases. In the United States alone, over 12% of women of reproductive age suffer from a chronic medical condition, especially diabetes and hypertension. Chronic diseases significantly increase the odds for poor maternal and newborn outcomes in pregnant women.

METHODS

A systematic review and meta-analysis of the evidence was conducted to ascertain the possible impact of preconception care for preventing and managing chronic diseases and promoting psychological health on maternal, newborn and child health outcomes. A comprehensive strategy was used to search electronic reference libraries, and both observational and clinical controlled trials were included. Cross-referencing and a separate search strategy for each preconception risk and intervention ensured wider study capture.

RESULTS

Maternal prepregnancy diabetic care is a significant intervention that reduces the occurrence of congenital malformations by 70% (95% Confidence Interval (CI): 59-78%) and perinatal mortality by 69% (95% CI: 47-81%). Furthermore, preconception management of epilepsy and phenylketonuria are essential and can optimize maternal, fetal and neonatal outcomes if given before conception. Ideally changes in antiepileptic drug therapy should be made at least 6 months before planned conception. Interventions specifically targeting women of reproductive age suffering from a psychiatric condition show that group-counseling and interventions leading to empowerment of women have reported non-significant reduction in depression (economic skill building: Mean Difference (MD) -7.53; 95% CI: -17.24, 2.18; counseling: MD-2.92; 95% CI: -13.17, 7.33).

CONCLUSION

While prevention and management of the chronic diseases like diabetes and hypertension, through counseling, and other dietary and pharmacological intervention, is important, delivering solutions to prevent and respond to women's psychological health problems are urgently needed to combat this leading cause of morbidity.

Establishing trimester-specific maternal thyroid function reference intervals

Background

Thyroid disorders are common in women of childbearing age and are associated with adverse pregnancy outcomes. Physiological changes in pregnancy and the lack of pregnancy-specific reference ranges make managing thyroid disorders in pregnancy challenging. Our aim was to establish trimester-specific thyroid function reference intervals throughout pregnancy, and to examine the prevalence of thyroid autoimmunity in otherwise euthyroid women.

Method

This was a prospective, cross-sectional study of thyroid function tests (TFTs) in pregnant women attending a large, tertiary referral maternity hospital. Patients with known thyroid disorders, autoimmune disease, recurrent miscarriage, hyperemesis gravidarum and pre-eclampsia were excluded. TFTs were analysed in the CUH biochemistry laboratory using Roche Modular E170 electrochemiluminescent immunoassay. Trimester-specific reference ranges (2.5th, 50th and 97.5th centiles) were calculated.

Results

Three-hundred-and-fifty-one women were included into the analysis. Median maternal age was 30. Thyroid-stimulating hormone concentrations showed slightly increasing median centile throughout gestation. Free thyroxine (T4) and T3 decreased throughout gestation. Table 1 demonstrates the calculated percentiles according to gestational weeks.

Conclusion

We established pregnancy-specific thyroid function reference intervals for our pregnant population, for use in clinical practice.

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.

The relationship of preconception thyrotropin levels to requirements for increasing the levothyroxine dose during pregnancy in women with primary hypothyroidism

BACKGROUND

Most women with hypothyroidism require an increase in their dose of levothyroxine (LT4) after conception. To minimize fetal and maternal complications of maternal hypothyroidism, it is thought that women should be rapidly restored to the euthyroid state. The objectives of this study was to determine the percentage of hypothyroid women who would need to increase their dose of LT4 dose even if they had a preconception (pre-C) serum thyrotropin (TSH) of <2.5 mIU/L as recommended by the Endocrine Society's guidelines and to ascertain whether there was a relationship between the pre-C TSH value and the need to increase the LT4 dose during pregnancy.

METHODS

Fifty-three pregnant women with hypothyroidism on LT4 treatment in whom the pre-C serum TSH was <2.5 mIU/L, but which was within the normal range, within the 6 months before pregnancy were retrospectively studied. An additional selection criterion was that their LT4 dose at the time of their first prenatal visit was the same as that received pre-C.

RESULTS

Seventeen patients had to increase their LT4 dose during pregnancy, because their serum TSH was increased at the time of the first prenatal visit (Group 1); and 36 patients did not have to increase their dose of LT4 during pregnancy (Group 2). The pre-C TSH was significantly higher in Group 1 (1.55 ± 0.62 mIU/L) than in Group 2 (0.98 ± 0.67 mIU/L). When pre-C TSH range was 1.2-2.4 mIU/L, 50% of the patients required an increase in the LT4 dose during pregnancy. In contrast, when the pre-C TSH was <1.2 mIU/L, only 17.2% (p< 0.02) had to increase the LT4 dose during pregnancy.

CONCLUSIONS

We suggest that in women with hypothyroidism who are planning to become pregnant, serum TSH levels should be in the normal range but should not be greater than about 1.2 mIU/mL.

The role of clinical guidelines in patient care: thyroid hormone replacement in women of reproductive age

BACKGROUND

Clinical guidelines have a role in medical education and in the standardization of patient care. However, it is not clear whether guidelines created by subspecialists reach relevant practicing physicians or influence patient care. In 2007 the Endocrine Society released "Guidelines on the Management of Thyroid Dysfunction During Pregnancy and Postpartum." The objective of this study was to characterize the role of these guidelines in provider education and in subsequent patient care decisions.

METHOD

In 2009 three waves of mail surveys were distributed to 1601 Wisconsin health care providers with a history of providing obstetric care. Survey participants were members of the American College of Obstetricians and Gynecologists or the American Academy of Family Physicians. There were 881 returned surveys (55%) and 575 were eligible for the study (adjusted rate 52.5%).

RESULTS

Although only 11.5% of providers read the Endocrine Society's guidelines, reading the guidelines was associated with increased likelihood of prepregnancy counseling on levothyroxine management (p < 0.0001), increased likelihood of screening for thyroid disease risk factors (p = 0.0007), and increased likelihood of empiric levothyroxine dose increase in pregnant patients (p = 0.0005). After controlling for provider sex, membership affiliation, practice setting, and number of years in practice, reading the guidelines was still an independent predictor of patient education prepregnancy (p < 0.01).

CONCLUSION

The Endocrine Society's "Guidelines on the Management of Thyroid Dysfunction During Pregnancy and Postpartum" reached a minority of providers involved in obstetrics, but exposure to the guidelines did impact patient care. A multidisciplinary approach to guideline creation would improve the dissemination and practical application of guidelines.