Hyperthyroidism is a condition where the thyroid gland shifts into overdrive, producing excess thyroid hormone. Though it affects only about 1% of Americans, its consequences can be profound, especially when left undiagnosed or untreated. Symptoms like unexplained weight loss, anxiety, and heart palpitations may appear subtle at first but can significantly reduce one's quality of life over time.
What's even more concerning is that an estimated 60% of individuals with thyroid disorders, including hyperthyroidism, are unaware of their condition. By being aware of the risk factors for hyperthyroidism, individuals can be more alert to the early signs of disease and seek medical attention before the condition worsens.
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Understanding Hyperthyroidism
The thyroid is a small, butterfly-shaped gland located in the neck. Don't let its size fool you – this small gland plays a big role in regulating metabolism and affects virtually every organ system.
The thyroid produces two main hormones:
- Thyroxine (T4): About 90% of the hormone the thyroid releases is T4, which has little biological activity. Once released into the bloodstream, T4 is converted into T3.
- Triiodothyronine (T3): The remaining 10% of thyroid hormone is released as T3. Despite being produced in smaller amounts, T3 is the biologically active form of thyroid hormone and has the greatest effect on speeding up metabolism.
In hyperthyroidism (overactive thyroid), the thyroid gland produces too much T3 and T4. This hormonal excess speeds up the body's metabolic processes, leading to a range of symptoms that can vary in severity.
Common symptoms include:
- Rapid (tachycardia) or irregular (arrhythmia) heartbeat
- Unexplained weight loss
- Nervousness, irritability, and anxiety
- Increased body temperature and sweating
- Tremors
- Difficulty sleeping (insomnia)
- Fatigue
- Muscle weakness
- Hair loss
- Diarrhea
- Menstrual irregularities
Left untreated, hyperthyroidism can lead to serious complications, including:
- Eye problems (thyroid eye disease)
- Heart issues
- Osteoporosis
- Infertility
- Thyroid storm: a life-threatening condition marked by an intense acceleration of hyperthyroid symptoms
Key Demographics at Risk for Hyperthyroidism
Now that we have a clear understanding of what hyperthyroidism is and how it affects the body, let's explore the key demographics at higher risk for developing the condition.
Gender: Women Are More at Risk
People assigned female at birth (AFAB) are more likely to develop hyperthyroidism than males, especially after pregnancy or menopause (58).
Experts say one in eight people AFAB will be affected by thyroid illness at some point during their life, and the risk of hyperthyroidism is ten times more than that of people assigned male at birth (AMAB).
This female predominance is attributed to sex differences in immune function and hormone levels (44).
Age: Middle-Aged and Older Adults
Hyperthyroidism affects up to 2.3% of older adults, and about 15% of cases of thyrotoxicosis (an excess of thyroid hormone in circulation) occur in individuals aged 60 or older (22).
Subclinical hyperthyroidism, a milder form where thyroid-stimulating hormone (TSH) levels are low but T3 and T4 remain normal, becomes more common with age, affecting up to 10% of the elderly population (22).
Graves' disease, the most common cause of hyperthyroidism, is most frequently diagnosed in people aged 30 to 50 (42). Toxic multinodular goiter (TMNG) and toxic adenoma are the other two most common causes of hyperthyroidism, with incidence rates peaking during the sixth and seventh decades of life (35, 36).
Family History and Genetics
Data from family and twin studies strongly suggest that genetics play a significant role in developing thyroid disease. Up to 50% of people with thyroid disease have another family member with a thyroid disorder.
Studies show that genetic influences account for 79% of the risk or predisposition for developing Graves' disease. Variations in genes, such as HLA-DR, can increase an individual's susceptibility to thyroid autoimmunity.
Medical Conditions and Risk Factors
Coexisting medical conditions and other risk factors further contribute to the likelihood of developing hyperthyroidism.
Autoimmune Disorders
The coexistence of multiple autoimmune diseases is observed in approximately 25% of patients with autoimmune conditions. The increased risk is likely due to shared genetic susceptibility factors that predispose to autoimmunity in general. Certain HLA alleles, as well as polymorphisms in genes like CTLA-4 and PTPN22, are associated with a higher risk of developing multiple autoimmune conditions. (4, 26)
People are at a higher risk of developing autoimmune thyroid disease (AITD) with a personal or family history of other autoimmune diseases, including:
- Type 1 diabetes (T1D)
- Rheumatoid arthritis (RA)
- Addison's disease
- Celiac disease
- Inflammatory bowel disease (IBD)
- Multiple sclerosis (MS)
- Systemic lupus erythematosus (SLE)
Personal History of Thyroid Issues
Thyroid nodules are discrete lumps within the thyroid gland and are extremely common. On autopsy, they are identified in up to 50% of people without previously diagnosed thyroid disease. (76)
While approximately 90% of detected thyroid nodules are clinically insignificant, some can contribute to hyperthyroidism (76). A "toxic" nodule is typically classified as either a toxic adenoma or part of a TMNG. In these cases, the nodule or nodules begin to autonomously produce thyroid hormones independent of the body's normal regulatory mechanisms. (45)
Individuals with hypothyroidism (underactive) who are prescribed thyroid hormone replacement therapy, such as levothyroxine, must be cautious, as inappropriate dosing can lead to hyperthyroidism. Healthcare providers should regularly monitor thyroid hormone levels in this population and adjust dosages as needed to avoid potential complications associated with over-replacement.
Pregnancy and Postpartum Period
Postpartum thyroiditis is an autoimmune disease that affects the thyroid gland after pregnancy and can cause thyroid dysfunction. It affects about 8% of women within the first year after delivery (47).
The disease generally follows a three-phase course, spontaneously resolving by 18 months postpartum (47, 52):
- Hyperthyroid Phase: inflammation of the thyroid causes the release of excess stored thyroid hormones
- Hypothyroid Phase: the thyroid gland underproduces thyroid hormones
- Euthyroid Phase: return to normal thyroid function
Environmental and Lifestyle Risk Factors
Environmental and lifestyle factors also influence the risk of hyperthyroidism, especially in genetically susceptible individuals.
Excessive Iodine Intake
Iodine is essential for the production of thyroid hormones T3 and T4. Without adequate iodine, the thyroid cannot function properly.
Iodine deficiency is a major cause of hypothyroidism worldwide. Thyroid nodules are also more likely to occur in regions where iodine deficiency is prevalent (76).
However, in iodine-sufficient areas, iodine excess is more likely to occur. Consuming too much iodine from sources like iodized salt, seaweed, certain medications (e.g., amiodarone), or supplements can affect the thyroid's ability to regulate hormone production, leading to Jod-Basedow phenomenon (iodine-induced hyperthyroidism). Iodine-induced hyperthyroidism is more likely to develop in those with preexisting thyroid conditions like Graves' disease or nodular goiter. (56)
Smoking
Smoking is a well-established environmental risk factor for Graves' disease. Research suggests that the more a person smokes – especially if they are a heavy smoker (smoking 25 or more cigarettes daily) – the greater their risk of developing Graves' disease.
In addition to increasing the risk of developing Graves' disease, smoking can also worsen its symptoms and complicate treatment. For instance, smokers may experience more severe eye-related complications, known as Graves' ophthalmopathy, which can lead to inflammation and damage to the tissues around the eyes.
Stress and Mental Health
Chronic stress significantly impacts thyroid health through the interplay of the hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-adrenal (HPT) axes (75).
When an individual experiences chronic stress, the body continuously releases cortisol. Prolonged elevations in cortisol can interfere with HPT signaling to the thyroid, exacerbate inflammation, and trigger autoimmune processes. Retrospective studies show that 80% of individuals report emotional stress before the onset of an autoimmune disease.
Even if patients don't specifically identify stress as the cause of hyperthyroidism, it can certainly worsen its symptoms, like difficulty sleeping, anxiety, and a racing heart.
Special Populations at Higher Risk
In this section, we focus on more nuanced populations that may be at an increased risk for developing hyperthyroidism.
People with a History of Radiation Exposure
Radiation, especially to the neck or chest area, is a well-established risk factor for thyroid autoimmunity and dysfunction. External or internal high-rose irradiation has been reported to induce Graves' disease in up to 5% of patients.
In a study of Hodgkin's lymphoma patients treated with radiation, 5% developed hyperthyroidism, with a mean time of eight years between diagnosis and hyperthyroidism onset. Risk factors included radiation dose greater than 35 Gy to the thyroid and less than three years since diagnosis.
Postmenopausal Women
The risk of developing thyroid disease tends to increase after menopause. This is largely due to hormonal changes during this transitional phase of a woman's life that can influence thyroid function, potentially exacerbating existing thyroid conditions or contributing to the development of new ones.
The symptoms of hyperthyroidism can closely resemble those commonly experienced during menopause, such as mood swings, hot flashes, and sleep disturbances (53). This overlap can make it challenging for women to recognize hyperthyroid symptoms as distinct from menopause-related changes, leading to a tendency to dismiss these symptoms as merely part of the normal aging process and delaying diagnosis.
When to Get Tested for Hyperthyroidism
The American Thyroid Association (ATA) recommends measuring thyroid function in all adults beginning at age 35 years and every five years thereafter. More frequent screening should be considered for high-risk individuals.
Patients experiencing symptoms of hyperthyroidism should talk to their doctors about ordering thyroid function tests to rule out hyperthyroidism.
While TSH is the preferred screening test for thyroid dysfunction, it can miss about 7% of cases of thyroid dysfunction. To increase testing accuracy, the ATA recommends ordering TSH with free T4 and total T3 (57).
Preventive Measures and Risk Management
By implementing these preventive measures, individuals can better manage their risk of developing hyperthyroidism and maintain overall thyroid health. Regular communication with your healthcare providers will help tailor these strategies to your individual health needs.
Regular Check-Ups
Individuals, especially those with a family or personal history of thyroid disease or other autoimmune conditions, should schedule regular medical check-ups with their doctor to monitor thyroid function. Early diagnosis can significantly improve treatment outcomes and prevent complications associated with untreated hyperthyroidism.
Managing Iodine Intake
Both iodine deficiency and excess can cause thyroid dysfunction, so monitoring your intake may be an important aspect of proactively supporting thyroid health.
- Always talk to your doctor before starting any iodine-containing medication or supplement.
- Patients with underlying thyroid conditions should consult their healthcare provider about the risks associated with iodinated contrast dyes used in certain imaging procedures. Studies indicate that exposure to iodinated contrast media is associated with a nearly two-fold increased risk of developing hyperthyroidism in patients without prior thyroid disease, and this risk is even more pronounced in those with existing thyroid conditions. (25, 55)
- Eat iodine-rich foods, including iodized salt, dairy, seafood, and seaweed, in moderation.
Healthy Lifestyle Choices
Adopting a healthy lifestyle to support thyroid health:
- Eat a balanced diet
- Exercise regularly to support metabolic health, immune function, and stress levels.
- Manage stress with techniques like mindfulness meditation, yoga, and deep breathing.
- Seek support to quit smoking
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Key Takeaways
- Hyperthyroidism is influenced by various demographics and risk factors that warrant attention. Key demographics and risk factors include age, gender, underlying medical conditions, and lifestyle factors.
- People who fall into high-risk categories – such as older adults, women, or individuals with a history of autoimmune conditions – should be proactive about routine thyroid screenings to safeguard thyroid health.
- Regular screenings and recognizing new symptoms can facilitate early detection and treatment of hyperthyroidism.
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