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Hypothyroidism

Disease Details

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Description: Hypothyroidism is a condition where the thyroid gland does not produce enough thyroid hormones, leading to a slowdown in the body's metabolic processes.
Type: Hypothyroidism is generally classified as an endocrine disorder. While it is often caused by autoimmune diseases like Hashimoto's thyroiditis, it can also result from other factors such as iodine deficiency or treatment for hyperthyroidism.

In terms of genetic transmission, hypothyroidism can have a hereditary component, particularly in cases of autoimmune thyroiditis. However, it is not inherited in a simple Mendelian fashion (i.e., not strictly autosomal dominant or recessive). Multiple genes and environmental factors can contribute to the risk of developing the disorder.
Signs And Symptoms: People with hypothyroidism often have no or only mild symptoms. Numerous symptoms and signs are associated with hypothyroidism and can be related to the underlying cause, or a direct effect of having not enough thyroid hormones. Hashimoto's thyroiditis may present with the mass effect of a goitre (enlarged thyroid gland). In middle-aged women, the symptoms may be mistaken for those of menopause.
Delayed relaxation after testing the ankle jerk reflex is a characteristic sign of hypothyroidism and is associated with the severity of the hormone deficit.
Prognosis: In hypothyroidism, the prognosis is generally favorable with proper treatment. Lifelong thyroid hormone replacement therapy, usually with levothyroxine, can effectively manage the condition. Once the appropriate dosage is found, individuals often lead normal, healthy lives with regular monitoring and minor adjustments in medication as needed. However, if left untreated, hypothyroidism can lead to complications such as cardiovascular issues, myxedema coma, and mental health problems. Regular follow-ups with a healthcare provider are essential for maintaining optimal thyroid function.
Onset: The onset of hypothyroidism can vary; it may develop slowly over several years. It often begins subtly, with symptoms such as fatigue, weight gain, and cold intolerance gradually becoming more noticeable. Depending on the cause, onset can be sudden (e.g., post-thyroidectomy) or chronic.

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Prevalence: The global prevalence of hypothyroidism varies widely, ranging from about 3% to 10% of the population, with higher rates in older adults and women. Specifically, in the United States, the prevalence is approximately 4.6%, affecting more women than men.
Epidemiology: Worldwide about one billion people are estimated to be iodine deficient; however, it is unknown how often this results in hypothyroidism. In large population-based studies in Western countries with sufficient dietary iodine, 0.3–0.4% of the population have overt hypothyroidism. A larger proportion, 4.3–8.5%, have subclinical hypothyroidism. Undiagnosed hypothyroidism is estimated to affect about 4–7% of community-derived populations in the US and Europe. Of people with subclinical hypothyroidism, 80% have a TSH level below the 10 mIU/L mark regarded as the threshold for treatment. Children with subclinical hypothyroidism often return to normal thyroid function, and a small proportion develops overt hypothyroidism (as predicted by evolving antibody and TSH levels, the presence of celiac disease, and the presence of a goitre).Women are more likely to develop hypothyroidism than men. In population-based studies, women were seven times more likely than men to have TSH levels above 10 mU/L. 2–4% of people with subclinical hypothyroidism will progress to overt hypothyroidism each year. The risk is higher in those with antibodies against thyroid peroxidase. Subclinical hypothyroidism is estimated to affect approximately 2% of children; in adults, subclinical hypothyroidism is more common in the elderly, and in White people. There is a much higher rate of thyroid disorders, the most common of which is hypothyroidism, in individuals with Down syndrome and Turner syndrome.Very severe hypothyroidism and myxedema coma are rare, with it estimated to occur in 0.22 per million people a year. The majority of cases occur in women over 60 years of age, although it may happen in all age groups.Most hypothyroidism is primary in nature. Central/secondary hypothyroidism affects 1:20,000 to 1:80,000 of the population, or about one out of every thousand people with hypothyroidism.
Intractability: Hypothyroidism is generally not considered intractable. It can typically be managed effectively with appropriate thyroid hormone replacement therapy. Most patients achieve good control of symptoms and normalization of thyroid hormone levels with medication, such as levothyroxine. Regular monitoring and dose adjustments may be required to maintain optimal thyroid function.
Disease Severity: Hypothyroidism is a condition where the thyroid gland does not produce enough thyroid hormones. The severity can vary based on hormone levels and symptoms.

- Mild (Subclinical): Few or no symptoms, slightly elevated TSH levels.
- Moderate: Noticeable symptoms like fatigue, weight gain, and depression, higher TSH and low T4 levels.
- Severe: Severe symptoms such as significant weight gain, slow heart rate, and potential myxedema coma, very high TSH and very low T4 levels.

Proper diagnosis and treatment are crucial to manage symptoms and prevent complications. Treatment usually involves thyroid hormone replacement therapy.
Healthcare Professionals: Disease Ontology ID - DOID:1459
Pathophysiology: Thyroid hormone is required for the normal functioning of numerous tissues in the body. In healthy individuals, the thyroid gland predominantly secretes thyroxine (T4), which is converted into triiodothyronine (T3) in other organs by the selenium-dependent enzyme iodothyronine deiodinase. Triiodothyronine binds to the thyroid hormone receptor in the nucleus of cells, where it stimulates the turning on of particular genes and the production of specific proteins. Additionally, the hormone binds to integrin αvβ3 on the cell membrane, thereby stimulating the sodium–hydrogen antiporter and processes such as formation of blood vessels and cell growth. In blood, almost all thyroid hormone (99.97%) are bound to plasma proteins such as thyroxine-binding globulin; only the free unbound thyroid hormone is biologically active.The thyroid gland is the only source of thyroid hormone in the body; the process requires iodine and the amino acid tyrosine. Iodine in the bloodstream is taken up by the gland and incorporated into thyroglobulin molecules. The process is controlled by the thyroid-stimulating hormone (TSH, thyrotropin), which is secreted by the pituitary. Not enough iodine, or not enough TSH, can result in decreased production of thyroid hormones.The hypothalamic–pituitary–thyroid axis plays a key role in maintaining thyroid hormone levels within normal limits. Production of TSH by the anterior pituitary gland is stimulated in turn by thyrotropin-releasing hormone (TRH), released from the hypothalamus. Production of TSH and TRH is decreased by thyroxine by a negative feedback process. Not enough TRH, which is uncommon, can lead to not enough TSH and thereby to not enough thyroid hormone production.Pregnancy leads to marked changes in thyroid hormone physiology. The gland is increased in size by 10%, thyroxine production is increased by 50%, and iodine requirements are increased. Many women have normal thyroid function but have immunological evidence of thyroid autoimmunity (as evidenced by autoantibodies) or are iodine deficient, and develop evidence of hypothyroidism before or after giving birth.
Carrier Status: Hypothyroidism is not typically considered in terms of "carrier status." Carrier status usually refers to individuals who carry one copy of a gene mutation that can cause a genetic disorder if two copies are present. Hypothyroidism is commonly caused by factors such as autoimmune disorders (like Hashimoto's thyroiditis), iodine deficiency, or damage to the thyroid gland. Therefore, the concept of carrier status does not apply to hypothyroidism. If you need more detailed information about the causes, symptoms, or treatment of hypothyroidism, please let me know.
Mechanism: Hypothyroidism is a condition characterized by an underactive thyroid gland that doesn't produce enough thyroid hormones. The mechanism and molecular mechanisms of hypothyroidism include:

**Mechanism:**
1. **Thyroid Hormone Production:** The thyroid gland produces two main hormones, Thyroxine (T4) and Triiodothyronine (T3). These hormones regulate the body's metabolism.
2. **Regulation by the Pituitary Gland:** The pituitary gland produces Thyroid Stimulating Hormone (TSH) which prompts the thyroid gland to produce T4 and T3.
3. **Feedback Loop:** A feedback loop maintains hormone levels. Low levels of T4 and T3 signal the pituitary gland to increase TSH production, and vice versa.

In hypothyroidism, there is a disruption in this process, leading to insufficient production of T4 and T3.

**Molecular Mechanisms:**
1. **Autoimmune Destruction (Hashimoto's Thyroiditis):** The most common cause, where the immune system produces antibodies against thyroid peroxidase (TPO) and thyroglobulin, proteins essential for thyroid hormone synthesis. This autoimmune attack damages thyroid cells, reducing hormone production.
2. **Thyroid Hormone Synthesis Defects:** Genetic mutations in the genes involved in thyroid hormone production, such as the TPO gene or the sodium/iodide symporter (NIS) gene, can impair hormone synthesis.
3. **Iodine Deficiency:** Iodine is crucial for T4 and T3 synthesis. Insufficient iodine intake leads to decreased thyroid hormone production.
4. **Medications and Treatments:** Certain medications (e.g., amiodarone, lithium) or treatments like radioactive iodine therapy and thyroid surgery can impair thyroid function.
5. **Pituitary or Hypothalamic Dysfunction:** Conditions affecting the pituitary gland (secondary hypothyroidism) or the hypothalamus (tertiary hypothyroidism) can reduce TSH production, impacting thyroid hormone synthesis.

Understanding these mechanisms helps in diagnosing, managing, and treating hypothyroidism effectively.
Treatment: Treatment for hypothyroidism primarily involves hormone replacement therapy. The standard treatment is levothyroxine, a synthetic form of the thyroid hormone thyroxine (T4). The goal is to normalize thyroid hormone levels, alleviate symptoms, and achieve a balance that allows the body's metabolism to function properly. Regular monitoring of thyroid function tests is necessary to adjust the dosage and ensure effectiveness. In most cases, treatment is lifelong.
Compassionate Use Treatment: Compassionate use treatments, off-label, and experimental treatments for hypothyroidism are generally limited because the condition is most commonly and effectively treated with standard thyroid hormone replacement therapies, such as levothyroxine. However, in certain specific or refractory cases, the following may be considered:

1. **Compassionate Use Treatments:**
- In rare cases where standard treatments are ineffective or cause adverse effects, healthcare providers might explore alternative thyroid hormone formulations under compassionate use protocols. This typically involves special approval from regulatory authorities.

2. **Off-label Treatments:**
- **Liothyronine (T3):** Although used primarily for hypothyroidism, combining liothyronine (T3) with levothyroxine (T4) is considered off-label. This combination can be beneficial for patients who don't fully respond to levothyroxine alone.
- **Desiccated Thyroid Extracts:** These are derived from the thyroid glands of pigs and contain a combination of T4 and T3. Some patients feel better on these animal-derived products, though they are not the first-line treatment.

3. **Experimental Treatments:**
- **Thyromimetics:** These are new types of drugs that mimic thyroid hormone activity and are currently under investigation for their efficacy and safety.
- **Gene Therapy:** Research is ongoing into gene therapy as a potential future treatment to directly address thyroid gland dysfunction.
- **Thyroid Gland Regeneration:** Experimental studies are examining stem cell therapy and regenerative medicine techniques to repair or regenerate thyroid tissue.

It is important to consult with a healthcare provider to discuss any alternative or experimental treatments, as they are not universally accepted or appropriate for all patients.
Lifestyle Recommendations: Lifestyle recommendations for hypothyroidism:

1. **Healthy Diet**: Consume a balanced diet rich in fruits, vegetables, lean proteins, whole grains, and healthy fats. Ensure adequate intake of iodine, selenium, and zinc, which are vital for thyroid function.
2. **Regular Exercise**: Engage in regular physical activity to help manage weight, improve mood, and boost energy levels. Aim for a mix of cardiovascular, strength training, and flexibility exercises.
3. **Medication Adherence**: Take your thyroid hormone replacement medication as prescribed, typically on an empty stomach, and avoid foods and supplements that can interfere with absorption.
4. **Stress Management**: Practice stress-reducing techniques like yoga, meditation, and deep-breathing exercises, as stress can negatively impact thyroid function.
5. **Regular Monitoring**: Have regular check-ups with your healthcare provider to monitor thyroid hormone levels and adjust treatment as necessary.
6. **Adequate Sleep**: Aim for 7-9 hours of quality sleep per night to support overall health and well-being.
7. **Avoid Goitrogenic Foods**: Limit intake of foods like cabbage, broccoli, cauliflower, and soy, which can interfere with thyroid function when consumed in large quantities.

These lifestyle changes can complement medical treatment and help manage hypothyroidism effectively.
Medication: The primary medication for hypothyroidism is levothyroxine. It is a synthetic form of the thyroid hormone thyroxine (T4) and helps replace the deficient hormone, thereby normalizing thyroid function and metabolism. The dosage is typically tailored to the individual's needs, based on regular monitoring of thyroid-stimulating hormone (TSH) levels.
Repurposable Drugs: Repurposable drugs for hypothyroidism include:

1. **Metformin** - Typically used for type 2 diabetes, it has shown potential in improving thyroid function in certain populations.
2. **Statins** - Commonly used to lower cholesterol, some studies suggest they may have a beneficial role in managing subclinical hypothyroidism.
3. **Guanfacine** - Primarily used for ADHD, it might be useful in specific hypothyroidism-related cases involving cognitive dysfunction.

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Metabolites: In hypothyroidism, several metabolites may be affected due to altered thyroid hormone levels. Notably, you may see:

1. **Elevated TSH (Thyroid Stimulating Hormone)**: This is often the primary indicator of hypothyroidism.
2. **Decreased free T4 (thyroxine)**: This is typically low in hypothyroidism as the thyroid gland fails to produce enough hormones.
3. **Decreased free T3 (triiodothyronine)**: T3 levels may also be decreased, though not always as significantly as T4.
4. **Increased cholesterol levels**: Hypothyroidism can lead to elevated total cholesterol and LDL cholesterol.
5. **Increased creatine kinase (CK)**: This enzyme can be elevated due to muscle effects in severe hypothyroidism.

These markers can assist in diagnosing and monitoring the management of hypothyroidism.
Nutraceuticals: For hypothyroidism, there is no definitive evidence that nutraceuticals can replace standard treatment. The primary treatment is usually levothyroxine, a synthetic thyroid hormone. However, some nutraceuticals like selenium, zinc, and iodine may support thyroid function, but they should be used cautiously and under medical supervision to avoid imbalances.

Nanotechnology is being researched to improve the delivery and effectiveness of thyroid medications, but it is not yet a standard treatment option. Potential applications include nanocarriers for more precise delivery of thyroid hormones and improvement in imaging for thyroid gland assessment.
Peptides: Hypothyroidism is characterized by an underactive thyroid gland, leading to low thyroid hormone production. Treatment with peptides is currently under research, but there is no established peptide-based therapy typically used in clinical practice. Nanotechnology is being explored for its potential to enhance drug delivery systems, including the targeted delivery of thyroid hormone replacements or peptides, potentially improving efficacy and reducing side effects. However, these approaches remain largely experimental.