Thyroid Status and Brain Circulation: The Rotterdam Study

Mapping Thyroid Hormone Action in the Human Brain

Background: Normal brain development, mood, and cognitive functions depend on thyroid hormone (TH) action. However, little is known about how TH mediates its actions in the human brain. This is due to limited access to human brains deprived of TH during fetal and early postnatal life, as well as from adults with altered thyroid status. One way to partially bypass these limitations is by using magnetic resonance imaging and spectroscopy, two neuroimaging techniques that provide detailed, noninvasive information on human brain structure and function. Another way is using human-induced pluripotent stem cell (hiPSCs)-derived three-dimensional in vitro systems, known as brain organoids, which allow for the study of fundamental aspects of the early stages of human brain development. Summary: This narrative review focuses on neuroimaging and brain organoid studies. Neuroimaging of human brains performed in individuals with different thyroid conditions provides information on the volume, myelination, blood flow, neural activity, and connectivity of different areas. Such studies show that suboptimal thyroid status can impact human brain development and its normal function throughout life. This is true not only for patients with sporadic congenital hypothyroidism, during pregnancy or early after birth, but also for adult patients with hypo- or hyperthyroidism, patients carrying mutations that manifest as impaired sensitivity to TH, and even for normal individuals during aging. Studies using brain organoids generated from hiPSCs of healthy individuals or patients with thyroid genetic conditions provide insights into how TH can impact the early development of the human cerebral cortex. Conclusions: The developmental alterations in children born to mothers with different degrees of gestational hypothyroidism or who developed hypothyroidism early in life are remarkable, affecting multiple brain regions and pathways, including the cerebral cortex, hippocampus, cerebellum, interhemispheric and corticospinal tracts, and associative nuclei. The data connecting such changes to poor neurological outcomes in adult patients with hypothyroidism represent an objective link between thyroid-specific functional brain alterations and behavior. Growing brain organoids require TH, which is critical for human neurogenesis and oligodendrogenesis. These models have proven useful in screening drugs with potential therapeutic effects for patients with genetic thyroid diseases.

Brain white matter alterations in young adult male patients with childhood-onset growth hormone deficiency: a diffusion tensor imaging study

PURPOSE

This study aimed to detect white matter changes and different effects of thyroid hormone on the white matter integrity in young adult male patients with childhood-onset growth hormone deficiency (CO-GHD), compared with healthy people.

METHODS

Magnetic resonance imaging (structural imaging and diffusion tensor imaging) was performed in 17 young adult male patients with CO-GHD and 17 healthy male controls. The white matter volume, mean diffusivity (MD) values and fractional anisotropy (FA) values were quantified and compared between two groups (CO-GHD group vs. control group). We assessed the interaction effects between thyroid hormone and groups (CO-GHD group vs. control group) on white matter integrity.

RESULTS

Patients with CO-GHD exhibited similar white matter volumes compared with controls. However, compared with the controls, patients with CO-GHD showed a significant reduction in FA values in six clusters and a substantial increase in MD values in four clusters, mainly involving the corticospinal tracts, corpus callosum and so on. Moreover, after correcting for insulin-like growth factor-1 levels, the significant interaction effects between groups (CO-GHD group vs. control group) and serum free thyroxine levels on MD values were noted in three clusters, mainly involving in superior longitudinal fasciculus and sagittal stratum.

CONCLUSION

In conclusion, young males with CO-GHD showed white matter changes in multiple brain regions and different effects of thyroid hormone on the white matter integrity.

The Rotterdam Study. Design update and major findings between 2020 and 2024

The Rotterdam Study is a population-based cohort study, started in 1990 in the district of Ommoord in the city of Rotterdam, the Netherlands, with the aim to describe the prevalence and incidence, unravel the etiology, and identify targets for prediction, prevention or intervention of multifactorial diseases in mid-life and elderly. The study currently includes 17,931 participants (overall response rate 65%), aged 40 years and over, who are examined in-person every 3 to 5 years in a dedicated research facility, and who are followed-up continuously through automated linkage with health care providers, both regionally and nationally. Research within the Rotterdam Study is carried out along two axes. First, research lines are oriented around diseases and clinical conditions, which are reflective of medical specializations. Second, cross-cutting research lines transverse these clinical demarcations allowing for inter- and multidisciplinary research. These research lines generally reflect subdomains within epidemiology. This paper describes recent methodological updates and main findings from each of these research lines. Also, future perspective for coming years highlighted.

Hyperthyroidism and cardiovascular disease: an association study using big data analytics

BACKGROUND

The cardiovascular (CV) system is profoundly affected by thyroid hormones. Both hypo- and hyperthyroidism can increase the risk of severe CV complications.

OBJECTIVE

To assess the association of hyperthyroidism with major CV risk factors (CVRFs) and CV diseases (CVDs) using a big data methodology with the Savana Manager platform.

MATERIAL AND METHODS

This was an observational and retrospective study. The data were obtained from the electronic medical records of the University Hospital Puerta de Hierro Majadahonda (Spain). Artificial intelligence techniques were used to extract the information from the electronic health records and Savana Manager 3.0 software was used for analysis.

RESULTS

Of a total of 540,939 patients studied (53.62% females; mean age 42.2 ± 8.7 years), 5504 patients (1.02%; 69.9% women) had a diagnosis of hyperthyroidism. Patients with this diagnosis had a significantly (p < 0.0001) higher frequency of CVRFs than that found in non-hyperthyroid subjects. The higher frequency of CVRFs in patients with hyperthyroidism was observed in both women and men and in patients younger and older than 65 years of age. The total frequency of CVDs was also significantly (p < 0.0001) higher in patients diagnosed with hyperthyroidism than that found in patients without this diagnosis. The highest odds ratio values obtained were 6.40 (4.27-9.61) for embolic stroke followed by 5.99 (5.62-6.38) for atrial fibrillation. The frequency of all CVDs evaluated in patients with a diagnosis of hyperthyroidism was significantly higher in both women and men, as well as in those younger and older than 65 years, compared to subjects without this diagnosis. A multivariate regression analysis showed that hyperthyroidism was significantly and independently associated with all the CVDs evaluated except for embolic stroke.

CONCLUSION

The data from this hospital cohort suggest that there is a significant association between the diagnosis of hyperthyroidism and the main CVRFs and CVDs in our population, regardless of the age and gender of the patients. Our study, in addition to confirming this association, provides useful information for understanding the applicability of artificial intelligence techniques to "real-world data and information".

Association of thyroid hormone sensitivity index with stroke in patients with coronary artery disease

BACKGROUND AND AIMS

Thyroid hormones (THs) will affect the occurrence and prognosis of stroke, and the research on THs sensitivity index and stroke in patients with coronary heart disease (CHD) is scarce. The goal of this study is to look into the relationship between central and peripheral THs sensitivity index and stroke in patients with CHD.

METHODS

Between January 1, 2014, and September 30, 2020, 30,160 patients with CHD were enrolled in this study. By computing the thyroid feedback quantile index (TFQI), thyroid stimulating hormone index (TSHI), and thyrotropin thyroxine resistance index (TT4RI), the central sensitivity indexes to THs was assessed, and the ratio of serum free triiodothyronine (FT3) to serum free thyroxine (FT4) was used to assess peripheral THs sensitivity. The relationship between central and peripheral THs sensitivity index and stroke was investigated using logistic regression, especially in different types of stroke, ages, sexes, and blood glucose levels.

RESULTS

Stroke risk is positive associated with TSHI, TFQI, and PTFQI. In subgroup analysis, the OR values of these relationships are higher in people younger than 65 years old, male, and diagnosed with diabetes. In addition, stroke risk was negatively associated with FT3/FT4, and the OR values of these relationships were lower in people older than 65 years, female, and diagnosed with prediabetes.

CONCLUSIONS

This study demonstrates that the increase in the central THs sensitivity index and the decrease in the peripheral THs sensitivity index are associated with a higher risk of stroke in CHD patients, and provides new ideas for the assessment of stroke in patients with CHD.

Exploring the causal factor effects of hypothyroidism on ischemic stroke: a two-sample Mendelian randomization study

Background

Observational studies have suggested a possible association between hypothyroidism and increased risk of ischemic stroke. However, a causal relationship remains unclear.

Methods

Data on single nucleotide polymorphisms (SNPs) associated with hypothyroidism and ischemic stroke were sourced from the FinnGens database and the UK Biobank of European descent. Both databases underwent separate two-sample Mendelian randomization (MR) analyses. A subsequent meta-analysis of MR results using a random-effects model was conducted to determine the causal relationship between hypothyroidism and ischemic stroke.

Results

All five analyses indicated a positive causal relationship between hypothyroidism and ischemic stroke. MR analysis of the association between hypothyroidism and ischemic stroke yielded a result of the inverse variance weighted (IVW) method at 4.7411 (1.3598-16.5308), p = 0.0146. The analysis of ischemic stroke (without excluding controls) yielded a result of the IVW method of 4.5713 (1.3570-15.3986), p = 0.0142. MR analysis with cerebral infarction yielded a result of the IVW method at 1.0110 (1.0006-1.0215), p = 0.0373. The MR analysis with cerebrovascular disease sequelae yielded an IVW method result of 2.4556 (1.0291-5.8595), p = 0.0429. Analysis for the sequelae of cerebrovascular disease (without excluding controls) yielded an IVW method result of 2.4217 (1.0217-5.7402), p = 0.0446. No evidence of heterogeneity or horizontal pleiotropy was found. The meta-analysis of the five MR results was 2.24 (1.18-4.26), p = 0.025.

Conclusion

Our two-sample Mendelian randomization study suggested a causal relationship between hypothyroidism and ischemic stroke, indicating that hypothyroidism could be a risk factor for ischemic stroke. However, further studies are required to elucidate the underlying biological mechanisms.

Cardiovascular and Neuronal Consequences of Thyroid Hormones Alterations in the Ischemic Stroke

Ischemic stroke is one of the leading global causes of neurological morbidity and decease. Its etiology depends on multiple events such as cardiac embolism, brain capillaries occlusion and atherosclerosis, which ultimately culminate in blood flow interruption, incurring hypoxia and nutrient deprivation. Thyroid hormones (THs) are pleiotropic modulators of several metabolic pathways, and critically influence different aspects of tissues development. The brain is a key TH target tissue and both hypo- and hyperthyroidism, during embryonic and adult life, are associated with deranged neuronal formation and cognitive functions. Accordingly, increasing pieces of evidence are drawing attention on the consistent relationship between the THs status and the acute cerebral and cardiac diseases. However, the concrete contribution of THs systemic or local alteration to the pathology outcome still needs to be fully addressed. In this review, we aim to summarize the multiple influences that THs exert on the brain and heart patho-physiology, to deepen the reasons for the harmful effects of hypo- and hyperthyroidism on these organs and to provide insights on the intricate relationship between the THs variations and the pathological alterations that take place after the ischemic injury.