Causes | Symptoms | Risk Factors | Epidemiology | Treatment | Conclusion
Overview
Hyperthyroidism and hypothyroidism are common endocrine disorders that affect the function of the thyroid gland.
These conditions can have lifelong effects on health, and their symptoms can significantly impact the quality of life.
Hyperthyroidism is characterized by the overproduction of thyroid hormones, while hypothyroidism results from underproduction.
Keep reading as we discuss the causes, symptoms, risk factors, and epidemiology of hyperthyroidism and hypothyroidism.
Causes
Hyperthyroidism is a medical condition that arises when the thyroid gland produces excessive thyroid hormone.
The thyroid is a small, butterfly-shaped gland situated at the base of the neck, which plays a crucial role in the body’s metabolism by producing two primary hormones: thyroxine (T-4) and triiodothyronine (T-3).
These hormones influence every cell in the body, affecting the body’s rate of utilizing fats and carbohydrates, regulating body temperature, impacting the heart rate, and determining how much protein the body produces.
When the thyroid releases too many of these hormones into the bloodstream, it can lead to various symptoms like weight loss, hand tremors, rapid or irregular heartbeat, nervousness, and increased sensitivity to heat, among others.[1]
Several conditions can result in hyperthyroidism, including:
- Graves’ Disease: This is the most common cause of hyperthyroidism. It’s an autoimmune disorder where the immune system attacks the thyroid gland, leading it to produce an excess amount of thyroid hormone.[1,2]
- Thyroid Nodules: Overactive thyroid nodules or lumps in the thyroid are usually non-cancerous. However, these nodules can occasionally become overactive and produce excessive thyroid hormones. Such overactive nodules
- are more commonly found in older adults.[2]
- Thyroiditis: This refers to the inflammation of the thyroid gland. Inflammation can cause stored thyroid hormone to leak out of the thyroid.[2]
- Excessive Iodine: The thyroid gland uses iodine to produce thyroid hormones. Consuming too much iodine in certain medicines, cough syrups, and some foods like seaweed can lead to an overactive thyroid.[3]
- Overmedication: People who take thyroid hormone medicine for hypothyroidism (an underactive thyroid) can develop hyperthyroidism if they consume too much of the medication.[3]
Hypothyroidism, commonly called an underactive thyroid, occurs when the thyroid gland does not produce enough thyroid hormone. This hormone plays a vital role as it influences every cell in the body, assisting in the rate at which the body uses fats and carbohydrates.[1]
There are several underlying causes for hypothyroidism:
- Hashimoto’s Disease: This is an autoimmune condition where the body’s immune system attacks the thyroid, leading to chronic inflammation and reduced thyroid function.[2]
- Thyroiditis: Thyroid inflammation can be due to various reasons, including postpartum inflammation.
- Congenital Hypothyroidism: A condition where infants are born with an underactive thyroid.
- Surgical Removal: Some people need to have part or all of their thyroid removed due to various conditions, after which the thyroid can no longer produce sufficient hormones.
- Radiation Treatment: Radiation treatments targeting the thyroid or surrounding areas, often used for cancers, can impair thyroid function.
- Medication Induced: Certain medicines can lead to reduced thyroid hormone production.
- Iodine Imbalance: Both excessive and deficient iodine levels in the diet can lead to thyroid issues.
- Pituitary Gland or Hypothalamus Disorders: Sometimes, the problem isn’t with the thyroid gland but the pituitary gland or hypothalamus, which regulates thyroid hormone levels.[2]
Symptoms
Both conditions present with a range of symptoms affecting various bodily systems:
Hyperthyroidism: Symptoms can range from increased heart rate, weight loss, excessive sweating, and nervousness to more severe symptoms like atrial fibrillation and congestive heart failure.
Hypothyroidism: It can manifest as fatigue, cold sensitivity, weight gain, joint pain, and depression, among other symptoms.
Risk Factors
While hyperthyroidism and hypothyroidism can arise from specific medical conditions and treatments, several general risk factors predispose individuals to these thyroid disorders:
- Age and Gender: People aged 50 and above are at higher risk, and women are more susceptible than men.[3]
- Autoimmune Diseases: Those with other autoimmune disorders are more likely to develop thyroid diseases.
- Medications: Some medications might interfere with thyroid function and result in hyperthyroidism or hypothyroidism.
- Family History: A history of thyroid disease in the family can increase an individual’s risk.
Epidemiology
Hyperthyroidism and hypothyroidism are prevalent in the U.S. Approximately 5% of U.S. adults either have thyroid disease or take thyroid medication.[3]
A specific study on adults aged 70 to 79 revealed that the prevalence of hyperthyroidism was higher among black women (9.7%) and white women (6%) compared to black men (3.2%) and white men (2.2%).
Conversely, hypothyroidism was more prevalent among white women (16.5%) and black women (6.2%), with white men (5.6%) and black men (1.7%) having a lesser prevalence.[3]
Treatment
Hyperthyroidism: Depending on its cause, treatments might include antithyroid medications, radioactive iodine, or surgery.
Hypothyroidism: The primary treatment involves daily use of the synthetic thyroid hormone levothyroxine, which restores adequate hormone levels, reversing the symptoms of hypothyroidism.
Conclusion
Understanding hyperthyroidism and hypothyroidism is crucial due to their widespread prevalence and potential to significantly impact the quality of life.
Effective diagnosis and timely treatment are essential to manage these conditions and prevent severe complications.
Considering the silent progression of these diseases, routine screening in specific populations might be beneficial to identify and address them in their subclinical stages.
References:
- Melish, J. S. (1990). Thyroid Disease. In H. K. Walker (Eds.) et. al., Clinical Methods: The History, Physical, and Laboratory Examinations. (3rd ed.). Butterworths.
- Doubleday, A. R., & Sippel, R. S. (2020). Hyperthyroidism. Gland surgery, 9(1), 124–135. https://doi.org/10.21037/gs.2019.11.01
- Mammen, J. S., McGready, J., Oxman, R., Chia, C. W., Ladenson, P. W., & Simonsick, E. M. (2015). Thyroid Hormone Therapy and Risk of Thyrotoxicosis in Community-Resident Older Adults: Findings from the Baltimore Longitudinal Study of Aging. Thyroid : official journal of the American Thyroid Association, 25(9), 979–986. https://doi.org/10.1089/thy.2015.0180
