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The thyroid gland, a key determinant of our health and well–being, undergoes significant changes as we age. These changes can have profound implications for our overall health, affecting everything from metabolism to cardiovascular health. This article will explore the aging–related changes to thyroid function, focusing on hormonal changes, symptoms, diagnosis, and treatment of hypothyroidism in seniors.
As the body ages, several changes in the thyroid are likely to occur:
- The thyroid becomes smaller and more difficult to feel manually in the neck. This change in the thyroid structure is a natural part of the aging process.
- Thyroid antibodies – including Thyroid Peroxidase (TPO) and Thyroglobulin (Tg) antibodies – which, when elevated, can both indicate autoimmune Hashimoto’s – tend to become more elevated over the age of 60. Elevated levels of these antibodies are associated with an increased risk of developing autoimmune thyroid disease.
- Levels of iodine – a necessary building block and ingredient of thyroid hormones – are lower. This decline in iodine levels can negatively affect the production of thyroid hormones.
- It takes a longer time for the body to produce thyroid hormones, including thyroxine (T4) and triiodothyronine (T3). This delay in hormone production results from the aging process affecting the thyroid gland.
- It takes longer to convert T4 into T3, the active thyroid hormone. This reduced conversion rate can impact the body’s metabolism and energy levels.
- Reverse T3 (rT3) levels increase. Elevated levels of rT3 can interfere with the action of T3, leading to potential metabolic effects.
- The 24-hour circadian rhythm of TSH production—present from birth on—fades and becomes less regular with age. This change in TSH production may impact the regulation of thyroid hormone levels in the body.
Hypothyroidism, an underactive thyroid, is more common in older adults, particularly women, and its prevalence increases with age. Several risk factors contribute to the development of hypothyroidism in older adults. It’s important to note, however, that while these risk factors increase the likelihood of developing hypothyroidism, they do not guarantee its occurrence. Regular check–ups and monitoring of thyroid function are essential, especially for those at higher risk.
Age and gender
Hypothyroidism is more common in older adults, especially women. The prevalence of hypothyroidism also increases with age.
The incidence of hypothyroidism rises due to the increasing prevalence of autoimmune thyroiditis with age. Other autoimmune diseases, such as type 1 diabetes or celiac disease, can also increase the risk of autoimmune Hashimoto’s.
A history of thyroid disease in close family members, such as a brother, sister, parent, or child of the patient, can indicate an increased risk of thyroid disease in an older patient.
Past treatment for hyperthyroidism
Individuals who have received treatment for hyperthyroidism – including partial thyroidectomy, antithyroid treatment, or radioactive iodine (RAI) – are at an increased risk of developing hypothyroidism.
Neck surgery or radiation treatment
A history of extensive surgery and/or radiation treatment to the neck can increase the risk of hypothyroidism. Specifically, external radiation therapy to the neck, often used in the treatment of head and neck cancer, can lead to damage to the thyroid gland, resulting in late-onset hypothyroidism.
Thyroid function declines with age, altering the hypothalamic–pituitary–thyroid (HPT) axis. Thyroid stimulating hormone (TSH) concentrations increase with age, and Free T3 and Free T4 levels tend to fall.
Interestingly, older individuals with declining thyroid function appear to have survival advantages compared to individuals with normal or high–normal thyroid function. In contrast, younger or middle-aged individuals with low-normal thyroid function suffer an increased risk of adverse cardiovascular and metabolic outcomes, while those with high–normal function have adverse bone outcomes, including osteoporosis and fractures.
Symptoms of hypothyroidism dysfunction in older adults can be subtle and often masquerade as diseases of the bowel, heart, or nervous system, making the condition challenging to diagnose.
Some older adults may have few hypothyroid symptoms, while others may experience symptoms similar to those in younger individuals. However, it’s not uncommon for symptoms to be atypical, further complicating diagnosis.
- Fatigue, sleepiness, and weakness: These are often reported by more than 50% of elderly patients.
- Weight gain: This is a common symptom, although not all older adults with hypothyroidism will experience it.
- Dry skin and coarse hair: These physical findings may be evident in hypothyroid elderly individuals.
- Constipation: An older person with hypothyroidism might have constipation because stool moves more slowly through the bowels.
- Cognitive decline: Memory loss or a decrease in cognitive function, often attributed to advancing age, may be the only symptoms of hypothyroidism present.
- Psychiatric problems: Clinical depression—a common symptom in younger people with hypothyroidism—can also affect older people with the condition. In some cases, it can be the only hypothyroidism symptom. Some older adults also develop psychosis with delusional behavior or hallucinations.
- Joint or muscle pain: Vague joint pain is a classic hypothyroidism symptom. It sometimes is the only symptom of hypothyroidism in an older person. Many people experience general muscle aches, particularly in large muscle groups like those in the legs.
- High cholesterol: Unexplained high cholesterol is sometimes the only evidence of an underactive thyroid in an older person.
It’s important to note that the presence of these symptoms does not definitively indicate hypothyroidism, as they can also be associated with other age–related conditions. Therefore, a thorough evaluation by a healthcare provider, including blood tests to check thyroid status and hormone levels, is necessary for an accurate diagnosis.
Diagnosing hypothyroidism in older adults can be challenging due to the subtlety of symptoms and the similarity of these symptoms to those of other age–related conditions. TSH measurement is considered the primary test for detecting hypothyroidism. Combined evaluations of TSH and Free T4 can detect overt hypothyroidism (high TSH with low Free T4 levels) and subclinical hypothyroidism (high TSH with normal Free T4 levels).
However, it’s important to understand that thyroid–stimulating hormone (TSH) and thyroxine (T4) reference ranges change as people age, particularly in those over 60 years old.
The normal range for TSH for adults under 60 is typically between 0.4 and 4.0 milliunits per liter (mU/L). But, based on understanding thyroid changes in aging, the National Academy of Clinical Biochemistry (NACB) formulated age-specific TSH reference ranges for the 65–70, 71–80, and >80 age groups. The normal age-specific distribution for the TSH reference for these age groups is as follows:
- 65–70 years: 0.65–5.51 mIU/L
- 71 to 80 years: 0.85–5.89 mIU/L
- Over 80 years: 0.78–6.70 mIU/L
These changes in TSH and T4 reference ranges with age have important clinical implications. If the same reference intervals used for younger patients are applied to older patients, there is a risk of over-diagnosing hypothyroidism, which could lead to unnecessary treatment with levothyroxine in the older population. Therefore, many studies suggest that age-specific reference ranges of TSH should be followed to avoid overtreatment of elderly patients.
Evaluations of these levels can detect both overt and subclinical hypothyroidism. Overt hypothyroidism is characterized by high TSH levels and low free–thyroxine levels, while subclinical hypothyroidism is characterized by elevated TSH levels with normal free–thyroxine levels.
It’s important to note that because TSH levels can increase with age, mild elevations do not necessarily reflect hypothyroidism. Furthermore, TSH can be transiently elevated in acute illness, so the diagnosis of hypothyroidism should be confirmed by persistently elevated TSH and decreased free T4 levels over time.
In some cases, neuropsychological testing may be used, as elderly patients with hypothyroidism have been found to score lower on mental status testing. However, there is no consensus on screening recommendations for asymptomatic older adults, but thyroid testing is warranted in any patient with a decline in clinical, cognitive, or functional status.
No specific guidelines exist for the treatment of hypothyroidism in seniors. There is general agreement, however, that people with TSH levels above 10 mIU/L should be treated, especially if they have any signs and symptoms of hypothyroidism or a family history of the condition.
Treatment for overt hypothyroidism includes thyroid hormone replacement medication. Levothyroxine is the drug of choice for seniors with hypothyroidism. Elderly patients require a low starting dose of levothyroxine. That dose is increased slowly, and levels are evaluated every 4 to 6 weeks until TSH levels are normalized. After stabilization, TSH levels are monitored yearly at a minimum.
The treatment of subclinical or mild hypothyroidism is more controversial. While treatment may result in lipid profile improvement, there is no evidence that this improvement is associated with decreased cardiovascular risk factors, a reduction in all-cause mortality risk, or improved quality of life in elderly patients.
Older hypothyroid patients also tend to be more sensitive to thyroid hormone replacement therapy. There are several things to consider when older hypothyroid patients start levothyroxine therapy:
- Problematic interactions with other medications, especially for chronic illnesses
- Different speeds of thyroid hormone clearance, which might lead to an increase in T4 levels
- Overtreatment can potentially worsen any preexisting heart problems and lead to new health problems, such as an irregular heartbeat (arrhythmia) and progressive bone loss
- Estrogen replacement therapy postmenopause might lead to a need for a higher dose of T4 therapy
Aging-related changes to thyroid function are complex and multifaceted, affecting various bodily functions and health outcomes. Understanding these changes is crucial for effectively diagnosing and treating thyroid disorders in elderly adults.
Paloma Health is an excellent medical practice for seniors with hypothyroidism due to our innovative approach to treatment and monitoring. As the first online medical practice focused on hypothyroidism, Paloma offers convenient access to thyroid function tests at home, medical guidance, and prescriptions from top thyroid practitioners. Paloma’s comprehensive approach includes regular testing, continuous supervision and management, and a focus on thyroid nutrition, providing integrated care for seniors with hypothyroidism. Additionally, Paloma Health takes a whole–body approach to long–term health and hypothyroidism, ensuring that seniors receive advanced and specialized care from a team dedicated to addressing the complexities of hypothyroidism and relieving persistent symptoms. Consider becoming a Paloma member today, and get started on optimal care for your underactive thyroid…at every age!