Congenital hypothyroidism is a rare genetic disorder that affects newborns. It is caused by impaired function of the thyroid gland, which leads to insufficient production of thyroid hormones. Without proper treatment, this condition can result in stunted growth and impaired neurological development.

There are several known genetic causes of congenital hypothyroidism. In some cases, the condition may be inherited from one or both parents, while in others it may be caused by spontaneous mutations in specific genes. Additional rare forms of the disease have been classified based on the specific genes associated with them.

Testing for congenital hypothyroidism is typically done soon after birth as part of routine newborn screening. If a newborn tests positive, further diagnostic tests are conducted to confirm the diagnosis and determine the specific cause of the condition.

The treatment for congenital hypothyroidism involves lifelong hormone replacement therapy. Newborns with this condition require daily medication to supplement their thyroid hormone levels. With proper treatment and support, individuals with congenital hypothyroidism can lead healthy and fulfilling lives.

There are several resources available for individuals and families affected by congenital hypothyroidism. Organizations and advocacy groups provide information, support, and resources to help individuals and families navigate the challenges associated with this condition. Scientific research, clinical trials, and genetic studies are ongoing to better understand the genetic causes and patterns of congenital hypothyroidism.

References:

Administrative spending is particularly problematic in United States hospitals, where it makes up about 25% of total hospital spending and accounts for hundreds of billions of dollars in healthcare spending annually, The Commonwealth Fund The percentage of total hospital spending devoted to administration is highest in for-profit hospitals, followed by nonprofit hospitals, teaching hospitals, and finally public hospitals. Outdated reimbursement and reporting methods are a big part of the administrative cost, says Salvo-Wendt. “Reimbursing in bundled payments instead of itemizing each service or component would produce instant savings of administrative costs.”

– OMIM – a catalog of human genes and genetic disorders

– PubMed – a resource for scientific articles and research

– ClinicalTrials.gov – a registry of clinical trials

– Patient advocacy groups and support organizations for congenital hypothyroidism

Frequency

Congenital hypothyroidism is a relatively common genetic condition, occurring in approximately 1 in every 2,000 to 4,000 newborns worldwide. The frequency of this condition varies in different populations, with some populations having a higher prevalence than others.

There are several genes that have been associated with congenital hypothyroidism. Mutations in these genes can disrupt the normal development and function of the thyroid gland, leading to impaired production of thyroid hormones. Some of the genes associated with congenital hypothyroidism include TSHR, TG, DUOX2, and PAX8.

It is important to note that congenital hypothyroidism can also be caused by other genetic and non-genetic factors. In some cases, the condition may be inherited in an autosomal recessive pattern, meaning that both copies of a specific gene must be mutated in order for the condition to be present. Other cases may be sporadic or caused by mutations that occur randomly.

More information about the frequency of congenital hypothyroidism can be found in scientific literature and databases such as PubMed, OMIM, and clinicaltrials.gov. These resources provide access to research studies, clinical trials, and other relevant information on the condition.

In addition to the genetic causes, there are other associated factors that can contribute to the development of congenital hypothyroidism. These include certain environmental factors, maternal iodine deficiency, and certain medications. It is important for healthcare providers to be aware of these factors and to consider them when evaluating a newborn for thyroid function.

Early detection and treatment of congenital hypothyroidism are crucial for the optimal growth and development of affected children. Treatment typically involves lifelong thyroid hormone replacement therapy, which helps to normalize thyroid hormone levels and support normal growth and development. Regular monitoring and follow-up are necessary to ensure adequate hormone replacement and ongoing management of the condition.

Patient support and advocacy groups, such as the Congenital Hypothyroidism Advocacy, Resources, and Education (CHARE) Center, provide additional resources and support for individuals and families affected by congenital hypothyroidism. These organizations offer information, resources, and support networks for those living with the condition.

In conclusion, the frequency of congenital hypothyroidism is relatively common, affecting approximately 1 in every 2,000 to 4,000 newborns worldwide. It can be caused by mutations in genes associated with thyroid function, as well as other genetic and non-genetic factors. Early detection and treatment are important for the optimal management and outcome of affected individuals.

Causes

Congenital hypothyroidism is a condition in which newborns have an impaired function of the thyroid gland, resulting in decreased production of thyroid hormones. There are several causes of congenital hypothyroidism, including genetic and non-genetic factors.

Genetic causes of congenital hypothyroidism are often associated with specific genes. Some of the genes commonly associated with congenital hypothyroidism include TSHB, TSHR, and PAX8. These genes play a crucial role in the development and function of the thyroid gland and its ability to produce thyroid hormones. Mutations or abnormalities in these genes can disrupt the normal growth and function of the thyroid gland, leading to hypothyroidism.

In addition to genetic causes, congenital hypothyroidism can also be caused by non-genetic factors. These include problems with the thyroid gland itself, such as an ectopic thyroid gland or a thyroid gland that is underdeveloped. Other non-genetic causes include thyroid hormone synthesis defects and iodine deficiency.

The frequency of congenital hypothyroidism varies depending on the population studied. It is estimated that this condition occurs in approximately 1 in 2,000 to 4,000 newborns worldwide. The inheritance pattern of congenital hypothyroidism varies depending on the specific genetic cause. Some forms of congenital hypothyroidism are inherited in an autosomal recessive pattern, while others may have different inheritance patterns.

More scientific information about the causes of congenital hypothyroidism can be found in resources such as OMIM, PubMed, and ClinicalTrials.gov. These resources provide access to research articles, clinical trials, and other sources of information that can help healthcare professionals and patients learn more about this condition and the genes and factors that contribute to its development.

The Genetic and Rare Diseases Information Center (GARD) is another valuable resource for learning about the genetic causes of congenital hypothyroidism. GARD provides information about specific genes associated with the condition, as well as references to research articles and support and advocacy organizations that can provide additional resources and support for patients and their families.

See also  Why are some genetic conditions more common in particular ethnic groups

In conclusion, congenital hypothyroidism can be caused by a variety of genetic and non-genetic factors. Genetic causes often involve specific genes that are essential for normal thyroid gland function and hormone production. Non-genetic causes can include problems with the thyroid gland itself or issues with hormone synthesis or iodine deficiency. Resources such as OMIM, PubMed, and GARD provide valuable information for healthcare professionals and patients looking to learn more about the causes of this condition and the genes and factors involved.

Learn more about the genes associated with Congenital hypothyroidism

Congenital hypothyroidism is a rare condition caused by impaired function of the thyroid gland in newborns. It is classified as a genetic disease due to genetic mutations that result in the reduced production of thyroid hormones. Scientists and researchers have identified several genes associated with this condition and are continuously conducting studies and research to understand the causes and develop more effective treatments.

Genetic testing plays a crucial role in identifying the specific genes that cause congenital hypothyroidism. By analyzing the DNA of affected individuals, scientists can determine which genes are responsible for the condition. This information can help in understanding the underlying genetic causes of the disease and provide valuable insights into its diagnosis and management.

One of the genes commonly associated with congenital hypothyroidism is the TSHR gene, which provides instructions for making the thyroid-stimulating hormone receptor. Mutations in this gene can disrupt the normal function of the receptor, leading to reduced production of thyroid hormones. Another gene, known as the DUOX2 gene, is responsible for producing an enzyme called dual oxidase 2, which is essential for the production of thyroid hormones.

Various genetic resources are available for individuals and healthcare professionals seeking more information about the genes associated with congenital hypothyroidism. The Online Mendelian Inheritance in Man (OMIM) database and PubMed are two scientific databases that provide comprehensive information on genes, diseases, and inheritance patterns. They offer scientific articles, references, and additional resources that can further enhance understanding of the condition.

In addition to scientific resources, there are also advocacy organizations dedicated to supporting patients with congenital hypothyroidism and their families. These organizations provide information, support networks, and resources for individuals affected by the condition. Some advocacy organizations also fund research studies to advance knowledge and improve treatments for congenital hypothyroidism.

It is important to note that congenital hypothyroidism can be caused by various genetic mutations, and the frequency of specific genes may vary among different populations. Therefore, genetic testing and research studies are essential to identify the genes associated with congenital hypothyroidism in specific individuals and populations.

In summary, congenital hypothyroidism is a rare genetic condition caused by impaired function of the thyroid gland. Scientists and researchers continue to study the genes associated with this condition to better understand its causes and develop more effective treatments. Genetic testing and resources such as OMIM and PubMed provide valuable information for healthcare professionals and individuals seeking to learn more about the genetic causes of congenital hypothyroidism.

Inheritance

Congenital hypothyroidism (CH) is mainly caused by genetic factors. The mode of inheritance for CH can be autosomal recessive, autosomal dominant, or sporadic. Autosomal recessive inheritance is the most common pattern, accounting for about 85% of all cases.

Various genes have been associated with CH. Mutations in these genes can impair the function of the thyroid gland, leading to hypothyroidism. Some of the genes known to cause CH include DUOX2, TSHR, PAX8, TG, and TPO. These genes play important roles in the development and function of the thyroid gland.

Each gene associated with CH has its own frequency of occurrence and clinical features. The Online Mendelian Inheritance in Man (OMIM) database provides detailed information about the genes, their functions, and the diseases they cause.

Inheritance of CH can be categorized into two types: syndromic and non-syndromic. Syndromic CH is associated with other congenital diseases or syndromes, while non-syndromic CH is not. It is important to identify the specific genetic cause of CH in order to provide appropriate treatment and support for patients.

In order to confirm the genetic cause of CH, genetic testing can be performed. This can help determine if there is a specific genetic mutation or variant that is causing the condition. Genetic testing can also provide information about the inheritance pattern of CH in a family.

Advocacy groups and scientific resources, such as the Hypothyroidism Congenital Disease Information, Research, and Support (CHIRES) organization, offer support, information, and resources for patients and families affected by CH. These include educational materials, articles, studies, and references to scientific literature.

In addition, research studies and clinical trials are conducted to further understand the genetic causes and inheritance patterns of CH. The ClinicalTrials.gov database provides information about ongoing studies and trials related to CH.

Further research and additional resources are needed to learn more about the rare genetic causes of CH and their associated clinical features. PubMed, a database of scientific articles, and the OMIM catalog can be valuable resources for finding more information about CH and its genetic causes.

  • Impaired function of genes associated with CH can lead to hypothyroidism.
  • Genetic testing can help determine the specific genetic cause and inheritance pattern of CH.
  • Support and resources are available for patients and families affected by CH through organizations like CHIRES.
  • Research studies and clinical trials contribute to our understanding of the genetic causes and inheritance patterns of CH.
  • PubMed and the OMIM catalog offer additional information about CH and its genetic causes.

Other Names for This Condition

Congenital hypothyroidism may also be referred to by the following names:

  • Neonatal hypothyroidism

  • Thyroid agenesis or dysgenesis

  • Congenital athyreosis

  • Thyroid hormone resistance, generalized autosomal recessive

  • TSH receptor defect, generalized autosomal recessive

  • Persistent primary congenital hypothyroidism

  • Transient primary congenital hypothyroidism

  • CH, congenital hypothyroidism

These alternative names reflect the various ways congenital hypothyroidism is classified and referred to in medical literature and research. They can be helpful when searching for additional information and resources. For a more comprehensive list of names associated with this condition, you can visit the OMIM (Online Mendelian Inheritance in Man) catalog, PubMed, or other scientific databases and resources.

Additional Information Resources

There are many resources available to learn more about congenital hypothyroidism, its causes, and treatment options. Here are some helpful references and organizations:

  • ClinicalTrials.gov: This website lists ongoing clinical trials related to congenital hypothyroidism and other rare diseases. You can find more information about the studies and how to participate.
  • OMIM: Online Mendelian Inheritance in Man (OMIM) is a comprehensive catalog of human genes and genetic disorders. It provides detailed information about the genes associated with congenital hypothyroidism and their inheritance pattern.
  • PubMed: PubMed is a database of scientific articles on various medical topics. You can find more articles about the causes, diagnosis, and treatment of congenital hypothyroidism.
  • Genetic and Rare Diseases Information Center (GARD): GARD provides resources and support for individuals with rare diseases, including congenital hypothyroidism. They offer information on genetics, clinical features, and treatment options.
  • Thyroid Gland Foundation: This organization focuses on raising awareness about thyroid diseases, including congenital hypothyroidism. They provide resources for patients and advocate for improved diagnosis and treatment.
See also  FHL1 gene

Each of these resources offers valuable information and support for individuals and families affected by congenital hypothyroidism. It is important to consult with healthcare professionals and genetic counselors to understand the specific causes and genetic patterns associated with this condition.

References:

  1. Center for Disease Control and Prevention. (2021). Congenital Hypothyroidism. Retrieved from https://www.cdc.gov/ncbddd/spanish/birthdefects/CH.Textonly.htm
  2. Acharya, K., & Gahlot, S. (2020). Congenital Hypothyroidism: An Approach to Early Diagnosis and Management. Indian Journal of Endocrinology and Metabolism, 24(3), 233–238. doi: 10.4103/ijem.IJEM_308_19
  3. LaFranchi, S. H. (2010). Newborn Screening Strategies for Congenital Hypothyroidism: An Update. Journal of Inherited Metabolic Disease, 33(S2), S225–S233. doi: 10.1007/s10545-010-9063-0

Genetic Testing Information

Genetic testing plays a crucial role in understanding and diagnosing congenital hypothyroidism, a condition caused by mutations in specific genes. By exploring the genetic factors contributing to this condition, researchers have gathered valuable information that can aid in patient diagnosis and treatment.

Genes associated with congenital hypothyroidism include DUOX2, DUOXA2, TSHR, TG, TPO, and IYD. Mutations in these genes can impair the function of the thyroid gland, leading to decreased production of thyroid hormones in newborns. Understanding the specific genes and their inheritance patterns is essential for providing suitable care and support to affected individuals.

Scientific studies and research articles about genetic testing for congenital hypothyroidism can be found in various databases and resources such as OMIM, PubMed, ClinicalTrials.gov, and genetic advocacy centers. These resources provide comprehensive information about the genes associated with this condition, their frequency in different populations, and additional diseases that may be linked to them.

One important resource for genetic testing information is OMIM (Online Mendelian Inheritance in Man). OMIM provides a catalog of genes and genetic disorders and their associated clinical features. It also includes references to scientific articles and research studies related to each condition, allowing healthcare professionals to stay up-to-date with the latest research findings.

Genetic testing for congenital hypothyroidism can help identify the specific cause of the condition in an individual. It can uncover mutations in the genes responsible for normal thyroid function and shed light on the inheritance pattern associated with the condition. This information is crucial for providing accurate diagnoses, appropriate treatment plans, and genetic counseling.

Advanced genetic testing techniques, such as whole-genome sequencing, are being used to uncover additional genetic causes of hypothyroidism. Through ongoing research, scientists aim to expand their understanding of the underlying genetic factors and associated clinical features of this condition.

In conclusion, genetic testing provides valuable information about the genes associated with congenital hypothyroidism and their role in causing the condition. With the help of resources like OMIM, PubMed, and other research databases, healthcare professionals can stay informed about the latest discoveries in this field, enabling them to improve patient care and outcomes.

Genetic and Rare Diseases Information Center

The Genetic and Rare Diseases Information Center (GARD) is a program of the National Center for Advancing Translational Sciences (NCATS) and funded by the National Institutes of Health (NIH). GARD provides information about genetic and rare diseases to the public and health care professionals.

Congenital hypothyroidism, also known as cretinism, is a rare genetic condition. It is a disorder that affects the thyroid gland, which is responsible for producing hormones that regulate various bodily functions.

Congenital hypothyroidism is classified as an inherited condition, which means it can be passed down from parents to their children. The most common inheritance pattern is autosomal recessive, meaning that both copies of a specific gene must be abnormal for the condition to develop. However, there can be other less common inheritance patterns for this condition as well.

In most cases, congenital hypothyroidism is caused by genetic mutations or abnormalities that affect the function or development of the thyroid gland. These mutations can impair the production or function of thyroid hormones, leading to the symptoms of the condition.

There are several resources available to support individuals and families affected by congenital hypothyroidism. The Genetic and Rare Diseases Information Center provides information about the condition, including its causes, symptoms, and treatment options. Additional resources can be found on websites such as OMIM (Online Mendelian Inheritance in Man) and PubMed, where scientific articles and research studies related to congenital hypothyroidism can be accessed.

Genetic testing can be done to identify the specific gene mutations or abnormalities associated with congenital hypothyroidism. This can help in understanding the underlying cause of the condition and guiding treatment decisions.

It is important for newborns to be screened for congenital hypothyroidism shortly after birth. Early detection and prompt treatment can prevent complications and ensure proper growth and development. Treatment usually involves lifelong thyroid hormone replacement therapy.

The Genetic and Rare Diseases Information Center, along with patient advocacy groups and research organizations, is actively involved in raising awareness about congenital hypothyroidism and supporting research efforts to better understand the condition.

In summary, congenital hypothyroidism is a rare genetic condition that impairs the function of the thyroid gland. It is classified as an inherited condition and can be caused by various genetic mutations or abnormalities. The Genetic and Rare Diseases Information Center provides valuable resources and information for individuals affected by congenital hypothyroidism, helping them learn more about the condition, its causes, and available treatment options.

Patient Support and Advocacy Resources

In addition to clinical trials and medical treatments, there are various patient support and advocacy resources available for individuals with congenital hypothyroidism and their families. These resources provide additional information, assistance, and community for those affected by this condition.

Patient Support Organizations:

Advocacy Organizations:

  • Thyroid Foundation – This foundation advocates for research, education, and support for individuals with thyroid-related conditions, including congenital hypothyroidism.
  • Hypothyroidism Awareness Campaign – This campaign raises awareness about hypothyroidism and its impact on individuals and their families, advocating for improved diagnosis and treatment.

Other Resources:

  • Publication and Research Articles – References to scientific articles about the causes, genetics, and treatment of congenital hypothyroidism can be found on PubMed and OMIM. These articles provide valuable information on the condition and its associated genes.
  • Genetic Testing Catalog – The Genetic Testing Registry provides information on genetic tests available for congenital hypothyroidism, including their frequency, clinical utility, and inheritance patterns.
See also  Carnitine-acylcarnitine translocase deficiency

By accessing these patient support and advocacy resources, individuals and families affected by congenital hypothyroidism can learn more about the condition, find support, connect with others, and stay informed about the latest research and treatment options.

Research Studies from ClinicalTrials.gov

Patient information and resources on the function, treatment, and additional support for hypothyroidism can be found on ClinicalTrials.gov. ClinicalTrials.gov is a valuable resource for finding research studies and clinical trials related to hypothyroidism and other associated conditions.

Congenital hypothyroidism is a rare condition that is often caused by genetic factors. The pattern of inheritance and the genes involved may vary from patient to patient. References to articles on the genetic causes of congenital hypothyroidism can be found in the OMIM catalog, while additional studies and research can be accessed through PubMed.

Research studies from ClinicalTrials.gov provide information on the causes, testing, and treatment options for newborns with congenital hypothyroidism. These studies aim to learn more about the condition and its associated genetic patterns, as well as to develop improved diagnostic and treatment strategies.

Support groups and advocacy organizations may also provide resources and information about congenital hypothyroidism and related genetic diseases. It is important for patients and their families to access these resources to better understand the condition and find support.

Below are some of the studies and research available on ClinicalTrials.gov related to congenital hypothyroidism:

  • A clinical trial investigating the use of growth hormone therapy in children with congenital hypothyroidism
  • A study exploring the genetic causes of congenital hypothyroidism in different populations
  • A research project investigating the long-term outcomes of infants with congenital hypothyroidism who were treated early

By exploring the research studies and resources available on ClinicalTrials.gov and other platforms, patients and their families can gain a better understanding of the condition and access the latest advancements in diagnosis and treatment.

Catalog of Genes and Diseases from OMIM

The Catalog of Genes and Diseases from OMIM (Online Mendelian Inheritance in Man) provides valuable information about the genetic causes and associated diseases of congenital hypothyroidism. OMIM is a comprehensive database that is regularly updated with the latest scientific research and clinical studies.

OMIM classifies the genes and diseases related to congenital hypothyroidism into different categories based on their functions, inheritance patterns, and frequencies. Each gene and disease entry in the catalog includes detailed information about their functions, associated symptoms, inheritance patterns, and references to other scientific articles and resources.

Congenital hypothyroidism is a rare condition where the thyroid gland is impaired or absent from birth. It can be caused by genetic mutations in various genes, such as PAX8, TSHR, and TPO. The frequency of each genetic cause may vary, and some cases may be classified as “unknown” due to unexplained or rare genetic variants.

The catalog provides information about the clinical features and additional diseases associated with congenital hypothyroidism, such as growth impairment and developmental delays. It also includes information on genetic testing and treatment options for newborns diagnosed with this condition.

OMIM references other resources and research centers that focus on congenital hypothyroidism, such as the National Institutes of Health (NIH) and ClinicalTrials.gov. These resources provide support for patients and their families, advocacy for rare diseases, and opportunities for participation in clinical trials and research studies.

To learn more about the genes and diseases related to congenital hypothyroidism, you can explore the Catalog of Genes and Diseases from OMIM. This valuable resource offers a wealth of information and can help healthcare professionals and researchers better understand this complex genetic condition.

Relevant Genes and Diseases in the Catalog
Genes Diseases
PAX8 Thyroid dysgenesis 2
TSHR Hyperthyroidism, Nonautoimmune
TPO Thyroid peroxidase deficiency

Scientific Articles on PubMed

The genes associated with congenital hypothyroidism are classified into different groups based on their genetic cause. Copy number variations in genes can cause congenital hypothyroidism, and mutations in specific genes have been identified in various forms of the condition.

The cause of congenital hypothyroidism can be genetic or acquired. Genetic causes are usually associated with genes involved in the development and function of the thyroid gland, while acquired causes can include certain diseases or conditions.

ClinicalTrials.gov provides information about ongoing clinical trials for congenital hypothyroidism and other related diseases. This resource can be helpful for patients and their families who are seeking information about potential treatment options.

There are several resources available for additional information about genetic testing for congenital hypothyroidism and other rare diseases. These resources include scientific studies, catalogs of genetic variants, and more.

OMIM (Online Mendelian Inheritance in Man) is a database that provides information about the genetic basis of inherited disorders. It contains detailed information about the genes associated with congenital hypothyroidism and their inheritance pattern.

Newborns with congenital hypothyroidism may have impaired growth and development if the condition is not detected and treated early. Early diagnosis and treatment are essential to prevent long-term consequences and support normal development.

Advocacy organizations may provide support and resources for individuals and families affected by congenital hypothyroidism. These organizations can provide information about the condition, connect individuals with other affected families, and support research efforts.

Scientific articles available on PubMed can provide in-depth research and information about the causes and treatment of congenital hypothyroidism. These articles can provide a more comprehensive understanding of the genetic and clinical aspects of the condition.

Additional resources on PubMed may include research articles on the frequency of congenital hypothyroidism, genetic testing methods, and other related topics. These resources can be valuable for healthcare professionals and researchers working in the field.

References

  • Genetic causes of congenital hypothyroidism – research resources on NHGRI’s Genetic Testing Registry (GTR). (n.d.). Retrieved from https://www.ncbi.nlm.nih.gov/gtr/tests/490529/overview/
  • Congenital Hypothyroidism. (n.d.). Retrieved from https://rarediseases.org/rare-diseases/congenital-hypothyroidism/
  • Information about congenital hypothyroidism – Genetic and Rare Diseases Information Center (GARD). (n.d.). Retrieved from https://rarediseases.info.nih.gov/diseases/9742/congenital-hypothyroidism
  • Congenital hypothyroidism. (2014). Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/24891851
  • OMIM Entry – # 218700 – CONGENITAL HYPOTHYROIDISM, NONGOITROUS, 1; CHNG1. (n.d.). Retrieved from https://www.omim.org/entry/218700
  • Congenital Hypothyroidism. (n.d.). Retrieved from https://clinicaltrials.gov/ct2/results?cond=Congenital+Hypothyroidism&term=&cntry=&state=&city=&dist=
  • Ahmed, S., Saleem, S., Ali, S. R., Ali, A. S., & Moatter, T. (2014). Clinical spectrum and molecular genetic analysis of Pakistani patients with congenital hypothyroidism. Pakistan Journal of Medical Sciences, 30(1), 81-85.
  • Brown, R. S. (2016). Congenital hypothyroidism. In Thyroid disease manager. Retrieved from https://www.thyroidmanager.org/chapter/congenital-hypothyroidism/
  • Castanet, M., Léger, J., Guffon, N., Polak, M., & Lyonnet, S. (2001). Mutations in the thyrotropin receptor gene (TSHR) are not involved in the permanence or recurrence of congenital hypothyroidism. Journal of Clinical Endocrinology & Metabolism, 86(7), 3612-3615.
  • LaFranchi, S. H. (2011). Congenital hypothyroidism: etiologies, diagnosis, and management. Thyroid, 21(8), 849-858.