Randomized Trial Comparing Two Algorithms for Levothyroxine Dose Adjustment in Pregnant Women With Primary Hypothyroidism

Emerging research themes in maternal hypothyroidism: a bibliometric exploration

Background

Hypothyroidism, a prevalent endocrine disorder, carries significant implications for maternal and infant health, especially in the context of maternal hypothyroidism. Despite a gradual surge in recent research, achieving a comprehensive understanding of the current state, focal points, and developmental trends in this field remains challenging. Clarifying these aspects and advancing research could notably enhance maternal-infant health outcomes. Therefore, this study employs bibliometric methods to systematically scrutinize maternal hypothyroidism research, serving as a reference for further investigations.

Objective

Through bibliometric analysis, this study seeks to unveil key research focus areas, developmental trends, and primary contributors in Maternal Hypothyroidism. The findings offer insights and recommendations to inform future research endeavors in this domain.

Methods

Literature metrics analysis was performed on data retrieved and extracted from the Web of Science Core Collection database. The analysis examined the evolution and thematic trends of literature related to Maternal Hypothyroidism. Data were collected on October 28, 2023, and bibliometric analysis was performed using VOSviewer, CiteSpace, and the Bibliometrix software package, considering specific characteristics such as publication year, country/region, institution, authorship, journals, references, and keywords.

Results

Retrieved from 1,078 journals, 4,184 articles were authored by 18,037 contributors in 4,580 institutions across 113 countries/regions on six continents. Maternal Hypothyroidism research publications surged from 44 to 310 annually, a 604.54% growth from 1991 to 2022. The USA (940 articles, 45,233 citations), China Medical University (82 articles, 2,176 citations), and Teng, Weiping (52 articles, 1,347 citations) emerged as the most productive country, institution, and author, respectively. "Thyroid" topped with 233 publications, followed by "Journal of Clinical Endocrinology & Metabolism" (202) with the most citations (18,513). "Pregnancy" was the most cited keyword, with recent high-frequency keywords such as "outcome," "gestational diabetes," "iodine intake," "preterm birth," "guideline," and "diagnosis" signaling emerging themes in Maternal Hypothyroidism.

Conclusions

This study unveils developmental trends, global collaboration patterns, foundational knowledge, and emerging frontiers in Maternal Hypothyroidism. Over 30 years, research has predominantly focused on aspects like diagnosis, treatment guidelines, thyroid function during pregnancy, and postpartum outcomes, with a central emphasis on the correlation between maternal and fetal health.

Under and overtreatment with thyroid hormone replacement during pregnancy

PURPOSE OF REVIEW

Among pregnant women on thyroid hormone replacement therapy undertreatment is common, while overtreatment is rare. Both deficient and excessive maternal thyroid hormone have been related to adverse maternofetal and long-term offspring outcomes, although studies' results are inconsistent. This review aims to discuss recent evidence regarding the effects of under- and overtreatment with thyroid hormone replacement during pregnancy and how current practices could be improved.

RECENT FINDINGS

Whether or not thyroid hormone therapy needs to be initiated for maternal subclinical hypothyroidism remains unclear, but recent meta-analyses have confirmed associations between adverse maternal, neonatal, and offspring outcomes in both overt and subclinical hypothyroidism. Subclinical hyperthyroidism in pregnancy is related to fewer adverse outcomes. Current adherence to levothyroxine during pregnancy and medication counseling by healthcare providers are suboptimal.

SUMMARY

Undertreatment of maternal hypothyroidism may increase risks for adverse maternofetal and offspring effects more than overtreatment does. If thyroid hormone replacement therapy is indicated and initiated in pregnancy, frequent thyroid function monitoring is required to avoid under- or overtreatment. Effective communication between clinicians and patients is imperative to increase medication adherence.

Preconception Counseling in Patients with Hypothyroidism and/or Thyroid Autoimmunity

Preconception counseling is an essential tool for preventing adverse pregnancy outcomes associated with thyroid dysfunction. The high prevalence of thyroid disease among women of reproductive age, and the increased risk of adverse pregnancy outcomes associated with thyroid dysfunction, emphasize the necessity for well-established screening and treatment criteria in the preconception period. We therefore conducted a literature review for relevant information on the screening, diagnosis and treatment of subclinical and overt hypothyroidism in women seeking pregnancy. While screening for thyroid disease is recommended only in the presence of risk factors, iodine supplementation should be recommended in most regions, with higher doses in areas with severe deficiency. Known hypothyroid women should be counseled about increasing their levothyroxine dose by 20–30% in the case of suspected or confirmed pregnancy (missed menstrual cycle or positive pregnancy test). Treating subclinical hypothyroidism appears to be beneficial, especially in the presence of autoimmunity or in patients undergoing artificial reproductive techniques. Regarding the management of TPOAb negative SCH women or euthyroid women with positive TPOAb, further research is necessary in order to make evidence-based recommendations.

Effect of Bisphenol A-Mediated RBP-4 on Pregnancy Outcomes in Nonobese Pregnant Female with Subclinical Hypothyroidism

Hypothyroidism is a systemic hypometabolic syndrome caused by the thyroxine resistance or a reduction in its extent. It is an endocrinopathy secondary to gestational diabetes and occurs usually without significant symptoms. This study explored the effect of bisphenol A (BPA)-mediated retinol-binding protein 4 (RBP-4) on pregnancy outcomes in a nonobese pregnant female with subclinical hypothyroidism. Three hundred nonobese pregnant females who had that established pregnancy files and had regular obstetric examinations from January 2021 to March 2022 were enrolled and classified with 100 cases in each group as early pregnancy (6–12 weeks of gestation), second-trimester (13–24 weeks of gestation), and third-trimester groups (25–36 weeks of gestation). Thirty pregnant women with subclinical hypothyroidism were selected as subjects, and another thirty pregnant women with normal thyroid function were selected as the normal control group. Thyroid function (thyroid-stimulating hormone (TSH), free triiodothyronine (FT₃), free T₄ (FT₄), and thyroid peroxidase antibody (TPO-Ab)) was measured by immunoelectrochemiluminescence. The level of BPA in urine was determined by solid-phase extraction high-performance liquid chromatography-tandem mass spectrometry. Serum RBP4 levels were determined by enzyme-linked immunosorbent assay. The level of TSH in the third-trimester group was higher than that in the first- and second-trimester groups, while the levels of FT₃, FT₄, and TPO-Ab were lower than those in the other two groups (P < 0.05). TSH in the second-trimester group was higher than that in the first-trimester group, while FT₃, FT₄, and TPO-Ab levels were lower than those in the first-trimester group (P < 0.05). The levels of BPA and RBP4 in gestational diabetes mellitus and hypertension were higher than those in the nongestational period, and the levels of BPA and RBP4 in gestational intrahepatic cholestasis and anemia were higher than those in the nongestational period, and the levels of BPA and RBP4 in preterm delivery were higher than those in nongestational period (P < 0.05). Also, the level of urinary BPA in the hypothyroidism group was higher than that in the normal control group (P < 0.05) and the level of serum RBP4 in the hypothyroidism group was higher than that in the normal control group (P < 0.05). According to multivariate logistic regression analysis, age ≥30 years and the ascending BPA and RBP4 were risk factors for subclinical hypothyroidism during pregnancy in the nonobese female. BPA and RBP-4 are closely related to the pregnancy outcome of nonobese subclinical hypothyroidism in the pregnant female. The degree of BPA and RBP-4 in adverse pregnancy outcomes is increased, which is the risk factor for nonobese subclinical hypothyroidism.

Recent Advances in Treatment of Recurrent Spontaneous Abortion

Importance

Recurrent spontaneous abortion (RSA) is a distressing condition experienced by approximately 1% of women trying to conceive. However, the treatment of RSA is a challenge both for clinicians and patients.

Objective

The aim of this review is to discuss the medical and surgical approach to the management of RSA, including those caused by anatomical, genetic, male, infectious, endocrine, and immune factors.

Evidence Acquisition

A literature search using MeSH terms for each topic was undertaken using PubMed, supplemented by hand searching for additional references. Retrieved articles were reviewed, synthesized, and summarized.

Results

Available treatments target hypothetical risk factors for RSA, although the effectiveness of many treatment options is controversial. Intervention should depend on the benefit-to-risk ratio of the proposed treatment.

Conclusions and Relevance

The etiology of RSA is heterogeneous, and patients often lack specific clinical manifestations, which has hindered the progress in predicting and preventing RSA to some extent. Despite intensive workup, at least 50% of couples do not have a clear underlying pathology. In addition, an evidence-based treatment is not available in most patients even if abnormal test results are present. Many new treatment directions are also still actively exploring; empirical and combined multiple treatments are still the main methods.

Target Audience

Obstetricians and gynecologists, family physicians.

Learning Objectives

After completing this activity, the learner should be better able to describe common risk factors for RSA; formulate individualized treatment plans to improve pregnancy outcomes; and propose supportive treatment recommendations for patients with unclear causes.

Weight-based thyroid dosing vs fixed dosing during pregnancy for subclinical hypothyroidism: A retrospective cohort study

OBJECTIVE

Thyroid hormones play a crucial role in foetal growth and neurocognitive development. Our aim was to compare a weight-based dosing method of starting thyroxine to a fixed-dose method in newly diagnosed women with subclinical hypothyroidism during pregnancy.

DESIGN

We performed a retrospective cohort study of consecutive women with newly diagnosed subclinical hypothyroidism during pregnancy seen at Mount Sinai Hospital and Women's College Hospital, Toronto, Canada 2015-2018.

PATIENTS

We identified women that were treated based on pre-pregnancy weight and those that were given a fixed dose of 50 mcg/day.

MEASUREMENTS

The percent of women who reached the target TSH of <2.5 mIU/L within 4-8 weeks was compared using a chi-squared test and a logistic regression model, adjusting for age, initial TSH and gestational age treatment was started.

RESULTS

393 women were included: 252 treated using a fixed-dose approach; 141 treated based on pre-pregnancy weight. In the unadjusted analysis, there was no difference between the groups in the percentage of women in the target range within 4-8 weeks (89.6% in the fixed-dose group vs 88.8% in the weight-based group (p = .954)). However, after adjustment for between-group differences in age, initial TSH and gestational age treatment was started, there was a significantly greater odds of achieving the target range using the weight-based dosing (OR 4.26 (1.60-11.7), p = .004).

CONCLUSIONS

Treating women with newly diagnosed subclinical hypothyroidism during pregnancy with a weight-based strategy increased the odds of reaching the target TSH range within 4-8 weeks. Clinicians caring for these women should consider this approach when starting treatment during pregnancy.

Thyroid disorders in subfertility and early pregnancy

Disorders of thyroid function are common in pregnancy and have implications for foetal and maternal health. Thyroid autoimmunity, as evidenced by the presence of elevated levels of anti-thyroid antibodies (anti-TPO and anti-Tg antibodies) is associated with an increased risk of miscarriage, though the mechanism remains poorly understood. There has been considerable focus on the implications and optimal management of pregnant women with thyroid disease, especially those undergoing assisted reproduction. Pregnancy results in significant changes in thyroid physiology and these need to be understood by clinicians involved in the care of pregnant women. Guidelines for the use of thyroxine and target thyroid function tests have been produced by international bodies but it is recognised that these predominantly reflect expert opinion rather than established evidence-based practice. Importantly a number of key clinical trials have been performed to aid understanding, particularly of the consequences of hypothyroidism for mother and baby, and the effectiveness of thyroid hormone use in autoimmune and subclinical hypothyroidism. This review summarises the current knowledge base and guidance for practice relating to thyroid disorders in pregnancy and subfertility.

Thyroid hormone therapy of hypothyroidism in pregnancy

Hypothyroidism is the most frequent pregnancy-related thyroid dysfunction, including overt and subclinical hypothyroidism. Studies show that even mild hypothyroidism may eventuate in adverse gestational outcomes and intellectual impairment of offspring. Women with overt hypothyroidism (OH) must be treated by levothyroxine (LT4) pre- and during pregnancy, however, it is controversial that when and how to initiate LT4 therapy and further optimize dosing so that pregnant women and their offspring may truly benefit. In the review we will analyze the changes in thyroid hormone requirements in pregnant women, the timing of LT4 treatment and adjustment of LT4 dose according to etiology in patients with hypothyroidism during pregnancy, and adjustment of LT4 after delivery.

Thyroid Nodules and Thyroid Cancer in the Pregnant Woman

Thyroid nodules and thyroid cancer are common conditions and may be identified during pregnancy. The comprehensive evaluation of thyroid nodules during pregnancy includes a medical history, physical examination, ultrasound assessment, and (when indicated) an ultrasound-guided fine-needle aspiration biopsy. Most thyroid cancers detected during pregnancy will not grow nor pose significant risk during gestation, and thyroid surgery in pregnant women poses higher risks than in nonpregnant women. Through a balanced and informed approach to the clinical care of this unique population, outcomes can be optimized for both the mother and the fetus.

Levothyroxine Dose Adjustment to Optimise Therapy Throughout a Patient's Lifetime

Levothyroxine is the standard therapy for patients with hypothyroidism, a condition that affects up to 5% of people worldwide. While levothyroxine therapy has substantially improved the lives of millions of hypothyroid patients since its introduction in 1949, the complexity of maintaining biochemical and clinical euthyroidism in patients undergoing treatment with levothyroxine cannot be underestimated. Initial dosing of levothyroxine can vary greatly and may be based on the amount of residual thyroid function retained by the patient, the body weight or lean body mass of the patient, and thyroid-stimulating hormone levels. As levothyroxine is usually administered over a patient’s lifetime, physiological changes throughout life will affect the dose of levothyroxine required to maintain euthyroidism. Furthermore, dose adjustments may need to be made in patients with concomitant medical conditions, in patients taking certain medications, as well as in elderly patients. Patients who have undergone any weight or hormonal changes may require dose adjustments, and the majority of pregnant women require increased doses of levothyroxine. Optimal treatment of hypothyroidism requires a partnership between patient and physician. The physician is tasked with vigilant appraisal of the patient’s status based on a thorough clinical and laboratory assessment and appropriate adjustment of their levothyroxine therapy. The patient in turn is tasked with medication adherence and reporting of symptomatology and any changes in their medical situation. The goal is consistent maintenance of euthyroidism, without the patient experiencing the adverse events and negative health consequences of under- or overtreatment.

Funding Merck.

Plain Language Summary Plain language summary available for this article.

Individualised requirements for optimum treatment of hypothyroidism: complex needs, limited options

Levothyroxine (LT4) therapy has a long history, a well-defined pharmacological profile and a favourable safety record in the alleviation of hypothyroidism. However, questions remain in defining the threshold for the requirement of treatment in patients with subclinical hypothyroidism, assessing the dose adequacy of the drug, and selecting the best treatment mode (LT4 monotherapy versus liothyronine [LT3]/LT4 combinations) for subpopulations with persisting complaints. Supplied as a prodrug, LT4 is enzymatically converted into the biologically more active thyroid hormone, triiodothyronine (T3). Importantly, tetraiodothyronine (T4) to T3 conversion efficiency may be impaired in patients receiving LT4, resulting in a loss of thyroid-stimulating hormone (TSH)-mediated feed-forward control of T3, alteration of the interlocking equilibria between serum concentrations of TSH, free thyroxine (FT4), and free triiodothyonine (FT3), and a decrease in FT3 to FT4 ratios. This downgrades the value of the TSH reference system derived in thyroid health for guiding the replacement dose in the treatment situation. Individualised conditionally defined setpoints may therefore provide appropriate biochemical targets to be clinically tested, together with a stronger focus on clinical presentation and future endpoint markers of tissue thyroid state. This cautionary note encompasses the use of aggregated statistical data from clinical trials which are not safely applicable to the individual level of patient care under these circumstances.

Subclinical Hypothyroidism in Women Planning Conception and During Pregnancy: Who Should Be Treated and How?

Subclinical hypothyroidism (SCH), a mild form of hypothyroidism defined as elevated TSH with normal free thyroxine levels, is a common diagnosis among women of reproductive age. In some, but not all, studies, it has been associated with infertility, an increased risk of adverse pregnancy and neonatal outcomes, and possibly with an increased risk of neurocognitive deficits in offspring. Despite well-established recommendations on treatment of overt hypothyroid pregnant women, a consensus has not yet been reached on whether to treat women with SCH. This review focuses on examining the evidence informing the clinical strategy for using levothyroxine (LT4) in women with SCH during pregnancy and those who are planning conception. A crucial first step is to accurately diagnose SCH using the appropriate population-based reference range. For pregnant women, if this is unavailable, the recommended TSH upper normal limit cutoff is 4.0 mIU/L. There is evidence supporting a decreased risk for pregnancy loss and preterm delivery for pregnant women with TSH > 4.0 mIU/L receiving LT4 therapy. LT4 treatment has been associated with better reproductive outcomes in women with SCH undergoing artificial reproductive techniques, but not in those who are attempting natural conception. Thyroid function tests need to be repeated throughout pregnancy to monitor LT4 therapy. In addition to potential harms, LT4 contributes to treatment burden. During a consultation, clinicians and patients should engage in a careful consideration of the current evidence in the context of the patients’ values and preferences to determine whether LT4 therapy initiation is the best next step.