Subclinical hypothyroidism in in vitro fertilization babies

Long-term health risk of offspring born from assisted reproductive technologies

Since the world's first in vitro fertilization baby was born in 1978, there have been more than 8 million children conceived through assisted reproductive technologies (ART) worldwide, and a significant proportion of them have reached puberty or young adulthood. Many studies have found that ART increases the risk of adverse perinatal outcomes, including preterm birth, low birth weight, small size for gestational age, perinatal mortality, and congenital anomalies. However, data regarding the long-term outcomes of ART offspring are limited. According to the developmental origins of health and disease theory, adverse environments during early life stages may induce adaptive changes and subsequently result in an increased risk of diseases in later life. Increasing evidence also suggests that ART offspring are predisposed to an increased risk of non-communicable diseases, such as malignancies, asthma, obesity, metabolic syndrome, diabetes, cardiovascular diseases, and neurodevelopmental and psychiatric disorders. In this review, we summarize the risks for long-term health in ART offspring, discuss the underlying mechanisms, including underlying parental infertility, epigenetic alterations, non-physiological hormone levels, and placental dysfunction, and propose potential strategies to optimize the management of ART and health care of parents and children to eliminate the associated risks. Further ongoing follow-up and research are warranted to determine the effects of ART on the long-term health of ART offspring in later life.

Congenital Hypothyroidism: Screening and Management

ABSTRACT

Untreated congenital hypothyroidism (CH) leads to intellectual disabilities. Prompt diagnosis by newborn screening (NBS) leading to early and adequate treatment results in grossly normal neurocognitive outcomes in adulthood. However, NBS for hypothyroidism is not yet established in all countries globally. Seventy percent of neonates worldwide do not undergo NBS.The initial treatment of CH is levothyroxine, 10 to 15 mcg/kg daily. The goals of treatment are to maintain consistent euthyroidism with normal thyroid-stimulating hormone and free thyroxine in the upper half of the age-specific reference range during the first 3 years of life. Controversy remains regarding detection of thyroid dysfunction and optimal management of special populations, including preterm or low-birth weight infants and infants with transient or mild CH, trisomy 21, or central hypothyroidism.Newborn screening alone is not sufficient to prevent adverse outcomes from CH in a pediatric population. In addition to NBS, the management of CH requires timely confirmation of the diagnosis, accurate interpretation of thyroid function testing, effective treatment, and consistent follow-up. Physicians need to consider hypothyroidism in the face of clinical symptoms, even if NBS thyroid test results are normal. When clinical symptoms and signs of hypothyroidism are present (such as large posterior fontanelle, large tongue, umbilical hernia, prolonged jaundice, constipation, lethargy, and/or hypothermia), measurement of serum thyroid-stimulating hormone and free thyroxine is indicated, regardless of NBS results.

The longer-term effects of IVF on offspring from childhood to adolescence

It is well established that there are increased pregnancy-related complications for a woman who conceives through assisted reproductive treatment (ART). Furthermore, it is known that the risk to the child born is greater, believed to be related to prematurity and growth restriction. Studies have also reported epigenetic changes in the DNA of offspring conceived through ART. In addition, it is believed that they have a greater risk of congenital malformations, although some of these risks may relate to underlying infertility, rather than the ART treatment per se. As a result, it may be expected that there is a greater risk to the longer-term health of the child who is born from ART; however, evidence about the long-term health of children conceived through ART is reassuring. Even though, it is recognised that many of the studies in this field come with limitations. Low numbers of participants is one of the major limitations, which makes subgroup analyses for diverse types of ART, or diverse types of infertility, not feasible. Furthermore, studies are often limited by short follow-up periods because of the difficulty and costs involved in longitudinal study designs. In addition, the rapid changes over time in ART limit the generalisability and significance of long-term findings. Well-designed studies investigating the long-term health outcomes of ART-conceived offspring and the potential influences of various aspects of the ART procedure, as well as studies of the potential underlying epigenetic mechanisms, are imperative. Furthermore, conclusions from childhood hospitalisation data from the United Kingdom, the long-term follow-up and quality of life study from researchers in Melbourne, and the data published from the Western Australian Growing Up Healthy Study will go a long way to help reassure current and prospective parents who may require ART to conceive.

OUP accepted manuscript

STUDY QUESTION

Are there differences in thyroid function between adolescents and young adults conceived with and without ART?

SUMMARY ANSWER

This study demonstrated no evidence of clinically relevant differences in thyroid function between adolescents and young adults conceived with and without ART.

WHAT IS KNOWN ALREADY

Studies to date have reported an increase in subclinical hypothyroidism in offspring conceived after ART. It has been suggested that the increase in maternal estrogen (E2) after fresh embryo transfers could affect thyroid function of the offspring. Suboptimal thyroid function at a young age can cause irreversible damage to the central nervous system, which makes early detection and correct treatment essential.

STUDY DESIGN, SIZE, DURATION

The Growing Up Healthy Study (GUHS) is a prospective cohort study, which aimed to recruit all adolescents born after conception with ART between 1991 and 2001 in the study area. The included participants (n = 303, aged 13–20 years) completed various health assessments. Depending on the age at enrolment, participants completed thyroid assessments at the 14- or 20-year follow-up. The outcomes of these replicated thyroid assessments were compared to those of participants conceived without ART from the Raine Study Generation 2 (Gen2). The Gen2 participants (n = 2868) were born between 1989 and 1992 and have been recognized to be representative of the local population.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Thyroid function assessments were compared between n = 134 GUHS and n = 1359 Gen2 adolescents at age 14 years and between n = 47 GUHS and n = 914 Gen2 young adults at age 20 years. The following mean thyroid hormone concentrations were compared between the cohorts: thyroid-stimulating hormone (TSH), free triiodothyronine (fT3), free thyroxine (fT4) and thyroid peroxidase antibodies (TPOAb). The prevalence of the following thyroid hormone profiles, based on individual thyroid hormone concentrations, was compared: euthyroidism, subclinical and overt hypo- and hyperthyroidism and thyroid autoimmunity. Outcomes were compared between the cohorts, and univariately between fresh embryo transfers (ET) and frozen ET (FET) within the GUHS. The correlation between maternal peak E2 concentrations (pE2) and fT4 was assessed within the GUHS.

MAIN RESULTS AND THE ROLE OF CHANCE

All mean thyroid function outcomes fell within the normal range. At both ages, we report no differences in TSH concentrations. At age 14 years, lower fT3 concentrations (4.80 versus 5.35 pmol/L, P < 0.001) and higher fT4 concentrations (12.76 versus 12.19 pmol/L, P < 0.001) were detected in the GUHS adolescents compared to Gen2 adolescents. At age 20 years, higher fT3 and fT4 concentrations were reported in GUHS adolescents (4.91 versus 4.63 pmol/L, P = 0.012; 13.43 versus 12.45 pmol/L, P < 0.001, respectively) compared to Gen2 participants. No differences in the prevalence of subclinical and overt hypo- and hyperthyroidism or thyroid autoimmunity were demonstrated between the cohorts at age 14 and 20 years. Thyroid function did not differ between ET and FET, and no correlation between pE2 and fT4 was reported.

LIMITATIONS, REASONS FOR CAUTION

The observational nature of the study limits the ability to prove causation. Furthermore, the comparison of ET and FET offspring at age 20 years may be lacking power. We were unable to differentiate between different types of ART (e.g. IVF versus ICSI) owing to the low number of ICSI cycles at the time of study. As ART laboratory and clinic data were collected contemporaneously with the time of treatment, no other data pertaining to the ART cycles were sought retrospectively; hence, some factors could not be accounted for.

WIDER IMPLICATIONS OF THE FINDINGS

This study does not support previous findings of clinically relevant differences in thyroid function when comparing a cohort of adolescents conceived after ART to counterparts conceived without ART. The minor differences detected in fT3 and fT4 were considered not biologically relevant. Although these findings appear reassuring, they warrant reinvestigation in adulthood.

STUDY FUNDING/COMPETING INTERESTS

This project was funded by an NHMRC Grant (Hart et al., ID 1042269). R.J.H. is the Medical Director of Fertility Specialists of Western Australia and a shareholder in Western IVF. He has received educational sponsorship from MSD, Merck-Serono and Ferring Pharmaceuticals. P.B. is the Scientific Director of Concept Fertility Centre, Subiaco, Western Australia. J.L.Y. is the Medical Director and a shareholder of PIVET Medical Centre, Perth, Western Australia.

TRIAL REGISTRATION NUMBER

N/A.

Alteration of Genomic Imprinting after Assisted Reproductive Technologies and Long-Term Health

Assisted reproductive technologies (ART) are the treatment of choice for some infertile couples and even though these procedures are generally considered safe, children conceived by ART have shown higher reported risks of some perinatal and postnatal complications such as low birth weight, preterm birth, and childhood cancer. In addition, the frequency of some congenital imprinting disorders, like Beckwith-Wiedemann Syndrome and Silver-Russell Syndrome, is higher than expected in the general population after ART. Experimental evidence from animal studies suggests that ART can induce stress in the embryo and influence gene expression and DNA methylation. Human epigenome studies have generally revealed an enrichment of alterations in imprinted regions in children conceived by ART, but no global methylation alterations. ART procedures occur simultaneously with the establishment and maintenance of imprinting during embryonic development, so this may underlie the apparent sensitivity of imprinted regions to ART. The impact in adulthood of imprinting alterations that occurred during early embryonic development is still unclear, but some experimental evidence in mice showed higher risk to obesity and cardiovascular disease after the restriction of some imprinted genes in early embryonic development. This supports the hypothesis that imprinting alterations in early development might induce epigenetic programming of metabolism and affect long-term health. Given the growing use of ART, it is important to determine the impact of ART in genomic imprinting and long-term health.

Thyroid function modifications in women undergoing controlled ovarian hyperstimulation for in vitro fertilization: a systematic review and meta-analysis

OBJECTIVE

To investigate the impact of controlled ovarian hyperstimulation (COH) for in vitro fertilization (IVF) on thyroid function.

DESIGN

Systematic review and meta-analysis.

SETTING

Not applicable.

PATIENT(S)

Infertile women undergoing conventional IVF or intracytoplasmic sperm injection.

INTERVENTION(S)

Systematic search of PubMed, MEDLINE, Embase, Scopus, and Web of Science from inception until November 2020. Studies could be included only if they met the following criteria: subjects were classified as euthyroid or hypothyroid; serum thyroid-stimulating hormone (TSH) and/or free thyroxine (FT4) levels were evaluated before COH; and the same thyroid function test was reassessed after COH (i.e., at the time of trigger for final follicle maturation and/or at pregnancy test).

MAIN OUTCOME MEASURE(S)

Mean difference (MD) between the serum TSH or FT4 levels assessed after COH and before COH.

RESULT(S)

In euthyroid women, the serum TSH levels assessed at the time of trigger and at the time of pregnancy test were significantly higher than those at baseline (MD: 0.69 mIU/L, 95% confidence interval [CI]: 0.30-1.08, I² = 93% and MD: 0.67, 95% CI: 0.49-0.85, I² = 72%, respectively). The serum FT4 levels did not undergo significant changes. Subanalysis confirmed an increase in the TSH level after restricting the analysis to women treated with gonadotropin-releasing hormone agonist protocols and to those who achieved pregnancy. A pronounced increase in the TSH level was observed in women treated for hypothyroidism (MD: 1.50 mIU/L, 95% CI: 1.10-1.89, I² = 0%).

CONCLUSION(S)

Pooling of the results showed a significant increase in serum TSH level in women undergoing COH for IVF. This change was particularly pronounced in women treated for hypothyroidism. New thyroid function screening strategies for women undergoing COH are warranted.

Increased blood pressure and impaired endothelial function after accelerated growth in IVF/ICSI children

STUDY QUESTION

What is the effect of growth velocity (height and weight) in early infancy on metabolic end-points and endothelial function in children born after ART?

SUMMARY ANSWER

Neonatal, infant and childhood growth is positively related to blood pressure in 9-year-old IVF/ICSI offspring, while growth in childhood was negatively associated with endothelial function.

WHAT IS KNOWN ALREADY

Offspring of pregnancies conceived after ART are at risk for later cardiometabolic risk factors. It is well established that early growth is related to numerous later cardiometabolic risk factors such as high blood pressure. This concept is known as the Developmental Origin of Health and Disease theory.

STUDY DESIGN SIZE DURATION

The relation between early growth and later cardiometabolic risk profile was studied in the MEDIUM-KIDS study, a prospective observational cohort study in children born after an IVF/ICSI treatment. In 131 children (48.1% males) at the average age of 9.4 years, cardiometabolic outcomes were assessed and growth data from birth until age 9 years were collected from child welfare centers.

PARTICIPANTS/MATERIALS SETTINGS METHODS

The following cardiometabolic outcomes were assessed: blood pressure, skinfolds, lipid spectrum, hair cortisone and glucose and insulin levels. Data on maximum skin perfusion after transdermal delivery of acetylcholine as a measure of endothelial function were collected.Growth charts were obtained electronically from child welfare centers, which offer free consultations and vaccinations to all Dutch children. At these centers, height and weight are recorded at predefined ages. Growth was defined as z-score difference in weight between two time points. Multivariable linear regression analysis was used to model the relation between growth and cardiometabolic outcomes. The following growth windows were -studied simultaneously in each model: 0-1 month, 1-3 months, 3-6 months, 6-11 months, 11-24 months and 2-6 years. The model was adjusted for height growth in all intervals except for 0-1 month.

MAIN RESULTS AND THE ROLE OF CHANCE

In multivariable linear regression analyses, multiple growth windows were positively associated with blood pressure, for example growth from 2-6 years was significantly related to systolic blood pressure: B = 4.13, P = 0.005. Maximum skin perfusion after acetylcholine was negatively associated with height-adjusted weight gain from 2 to 6 years: B = -0.09 (log scale), P = 0.03. Several growth windows (weight 1-3 months, 3-6 months, 6-11 months, 11-24 months, 2-6 years) were positively linked with total adiposity. Lipids, glucose tolerance indices and cortisone were not related to growth.

LIMITATIONS REASONS FOR CAUTION

This study is of modest size and of observational nature, and we did not include a control group. Therefore, we cannot assess whether the observed associations are causal. It is also not possible to analyze if our observations are specific for, or exacerbated in, the ART population. Ideally, a control group of naturally conceived siblings of IVF/ICSI children should simultaneously be studied to address this limitation and to assess the impact of the ART procedure without the influence of parental (subfertility) characteristics.

WIDER IMPLICATIONS OF THE FINDINGS

The results of this study contribute to our understanding of the reported increased risk for hypertension in ART offspring. We speculate that early, accelerated growth may be involved in the reported increased risk for hypertension in ART offspring, with endothelial dysfunction as a possible underlying mechanism. However, additional research into the mechanisms involved is required.

STUDY FUNDING/COMPETING INTERESTS

The study was financially supported by the March of Dimes, grant number #6-FY13-153. The sponsor of the study had no role in study design, data collection, data analysis, data interpretation or writing of the paper. The authors have no conflict of interest to declare.

TRIAL REGISTRATION NUMBER

NTR4220.

Higher Incidence Rates of Hypothyroidism and Late TSH Rise in Preterm Very-Low-Birth-Weight Infants at a Tertiary Care Center

BACKGROUND/AIMS

Preterm newborns with a very low birth weight (VLBW) of < 1,500 g have an atypical form of hypothyroidism with a delayed rise in TSH, necessitating a second newborn screening specimen collection. The aims of this study were to survey the compliance with second newborn screening to detect delayed TSH rise in VLBW preterm infants at a tertiary care center, and to determine the rate of atypical hypothyroidism.

METHODS

Retrospective review of the records of 104 preterm VLBW infants. Late TSH rise was defined as an increase in TSH concentration after 14 days of age in the presence of a normal initial screen.

RESULTS

The compliance rate was 92% for the second screening. High rates of hypothyroidism (16.3%) and of late TSH rise (4.8%) were detected. Patients with hypothyroidism had a significantly lower birth weight (p = 0.01) and longer hospital stay (p = 0.004). Patients with late versus those with early TSH rise had a significantly lower mean birth weight (851 ± 302 vs. 1,191 ± 121 g, p = 0.004).

CONCLUSION

The rates of early and late TSH rise in this VLBW population were higher than those in the literature and could be due to the use of povidone-iodine disinfectants. The yield of a second TSH screening in this study was high indicating the need for vigilance in screening VLBW preterm infants.

Mild Hypothyroidism in Childhood: Who, When, and How Should Be Treated?

Mild hypothyroidism, also known as subclinical hypothyroidism (SH), is biochemically defined as serum TSH levels above the upper limit of the reference range, in the presence of normal serum concentrations of total T4 and free T4 (FT4). In the neonatal period, mild hypothyroidism can be defined by the presence of a TSH value between 6 and 20 mIU/L and normal FT4 levels. After the neonatal period, SH can be defined mild if TSH ranges between 4.5 and 10 mIU/L. The management of mild hypothyroidism in childhood is challenging. The major concern is to establish whether this condition should always be considered an expression of mild thyroid dysfunction. Indeed, the effects of untreated mild hypothyroidism are still not completely defined. In the neonatal period, concern exists about neurocognitive outcome; in children, although there is no clear evidence of alterations in growth or neurocognitive development, subtle cardiovascular abnormalities have been documented. Therefore, there is still uncertainty about the need of treatment across all ages, and the management should be based on the age of the child, the etiology, and the degree of TSH elevation, as well as on other patient factors. This review updates current evidences on diagnosis and management of mild hypothyroidism in childhood.

The health outcomes of human offspring conceived by assisted reproductive technologies (ART)

Concerns have been raised about the health and development of children conceived by assisted reproductive technologies (ART) since 1978. Controversially, ART has been linked with adverse obstetric and perinatal outcomes, an increased risk of birth defects, cancers, and growth and development disorders. Emerging evidence suggests that ART treatment may also predispose individuals to an increased risk of chronic ageing related diseases such as obesity, type 2 diabetes and cardiovascular disease. This review will summarize the available evidence on the short-term and long-term health outcomes of ART singletons, as multiple pregnancies after multiple embryos transfer, are associated with low birth weight and preterm delivery, which can separately increase risk of adverse postnatal outcomes, and impact long-term health. We will also examine the potential factors that may contribute to these health risks, and discuss underlying mechanisms, including epigenetic changes that may occur during the preimplantation period and reprogram development in utero, and adult health, later in life. Lastly, this review will consider the future directions with the view to optimize the long-term health of ART children.

Transient neonatal hyperthyrotropinemia is a risk factor for developing persistent hyperthyrotropinemia in childhood with repercussion on developmental status

OBJECTIVE

Transient neonatal hyperthyrotropinemia (TNH) is defined as a neonatal abnormality of thyroid function, which reverts to normal at re-examination after 2 weeks of life. The thyroid function of these infants has not been sufficiently studied in terms of the risk of developing persistent hyperthyrotropinemia (PH) in later childhood and its impact on growth and development.

DESIGN

A prospective cohort study included all babies born in our hospital between 2001 and 2006 and screened for hypothyroidism, whose thyroid function was re-examined 6 years later. Exclusion criteria included the following conditions: preterm birth, birth weight <2500 g, Down's syndrome, descendants of mothers with immune thyroid disease, congenital malformations, cardiac, renal, hepatic, and metabolic diseases, and steroid or dopamine medication. The variables included are TSH and thyroxine at neonatal screening and 6 years later. Main outcomes are the risk of developing PH in childhood, linear growth, and development using Parents' Evaluation of Developmental Status (PEDS).

RESULTS

Out of 5040 normal-term newborns, 301 (6.0%, 95% CI 5.3-6.6%) have TSH ≥10 mU/l (TNH). Six years later, we re-examined 65 randomly selected children with TNH and 185 controls. In the TNH cohort, we found six out of 65 children (9.2%, 95% CI 1.4-17.0%) with PH (TSH ≥6.4 mU/l), and three out of 185 (1.6%, 95% CI 0.3-4.7%) among controls, relative risk 5.7 (95% CI 1.5-22.1), P=0.0114. TSH and developmental delay were found to be significantly higher in the TNH cohort (4.7±1.3 mU/l vs 2.1±0.5 mU/l, P<0.0001 and 15/65 (23%, 95% CI 12-34.1) vs 21/185 (11.3%, 95% CI 6.5-16.2) P=0.0348).

CONCLUSIONS

Newborns with TNH have a higher risk of developing PH in childhood, with repercussion on developmental status.

Subclinical hypothyroidism in children and adolescents: is it clinically relevant?

Although subclinical hypothyroidism (SH) is a common clinical problem, its diagnosis tends to be incidental. According to the definition, it should be asymptomatic, only detectable by screening. The presence or coincidence of any symptoms leads to L-thyroxine treatment. The clinical presentation, especially in younger patients with subclinical hypothyroidism, is still under dispute. Accordingly, the aim of this paper was to review the literature from the past seven years. The literature search identified 1,594 potentially relevant articles, of which 24 met the inclusion criteria. Few studies focus on the symptomatology of subclinical hypothyroidism, and most of them analyzed a small number of subjects. A significant correlation was found by some authors between subclinical hypothyroidism and a higher risk of hypertension, dyslipidemia, and migraine. No evidence of the impact of subclinical hypothyroidism on weight, growth velocity, and puberty was revealed. As the quality of most studies is poor and no definite conclusions can be drawn, randomized, large-scale studies in children and adolescents are warranted to determine the best care for patients with SH.

IVF and breast cancer: a systematic review and meta-analysis

BACKGROUND

The effects of controlled ovarian hyperstimulation (COH) for IVF in terms of breast cancer risk remain controversial, despite the hormone-dependent nature of the latter.

METHODS

Eligible studies up to 15 February 2013 were identified and pooled effect estimates for relative risk (RR) were calculated separately for the investigations using the general population and those using infertile women, as a reference group. Fixed- or random-effects models were implemented and subgroup analyses were performed, as appropriate.

RESULTS

Eight cohort studies were synthesized, yielding a total cohort size of 1,554,332 women among whom 14,961 incident breast cancer cases occurred, encompassing 576 incident breast cancer cases among women exposed to IVF. No significant association between IVF and breast cancer was observed either in the group of studies treating the general population (RR = 0.91, 95% confidence interval (CI): 0.74-1.11) or infertile women (RR = 1.02, 95% CI: 0.88-1.18), as a reference group. Of note were the marginal associations, protective for pregnant and/or parous women after IVF (pooled effect estimate = 0.86, 95% CI: 0.73-1.01) and adverse for women <30 years at first IVF treatment (pooled effect estimate = 1.64, 95% CI: 0.96-2.80).

CONCLUSIONS

At present, COH for IVF does not seem to impart increased breast cancer risk. Longer follow-up periods, comparisons versus infertile women, subgroup analyses aiming to trace vulnerable subgroups, adjustment for various confounders and larger informative data sets are needed before conclusive statements for the safety of the procedure are reached.