Stroke And Thyroid: Is There A Link?

can a stroke affect your thyroid

The thyroid and the brain are both vital organs in the human body. Thyroid hormones have a complex relationship with ischemic stroke and stroke recovery. Untreated hypothyroidism can increase the risk of developing heart disease due to increased levels of bad cholesterol, which can lead to atherosclerosis, or hardening of the arteries, and subsequently increase the risk of strokes. Additionally, hypothyroidism is associated with hyperhomocysteinemia, which is a risk factor for stroke. Hypothyroidism can also cause atrial fibrillation, which is a common cause of cardioembolic stroke. However, more research is needed to establish a direct causal link between thyroid function and stroke outcomes.

Characteristics Values
Stroke Fifth leading cause of death and the primary cause of long-term adult disability in the United States
Thyroid Hypothyroidism can cause hypertension, hypercholesterolemia, cardiac dysfunction, and both hypo- and hypercoagulability, all of which are risk factors for stroke
Thyroid hormones and stroke Lower levels of free T3 are associated with a poorer prognosis at hospital discharge, and at 3 and 12 months post-stroke
Hypothyroidism and stroke Hypothyroidism is common in patients with acute ischemic stroke (AIS) and transient ischemic attack (TIA)

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Hypothyroidism and hyperthyroidism can increase the risk of stroke

Several factors contribute to the link between hypothyroidism and stroke. Firstly, hypothyroidism can lead to hypertension or high blood pressure, which is a significant risk factor for stroke. The imbalance of thyroid hormones can cause a decrease in blood vessel elasticity and an increase in peripheral resistance, resulting in elevated blood pressure. Secondly, hypothyroidism is associated with hypercholesterolemia or high cholesterol levels. It can lead to increased levels of low-density lipoprotein (LDL) cholesterol, which contributes to plaque formation and atherosclerosis. Atherosclerosis narrows the blood vessels, making them more susceptible to blockages that can cause strokes. Thirdly, hypothyroidism can lead to changes in cardiac function, including diastolic dysfunction and reduced cardiac output. Alterations in cardiac function further increase the risk of stroke. Lastly, hypothyroidism affects blood clotting factors, making individuals more prone to forming blood clots. This, in turn, increases the likelihood of a clot travelling to the brain and causing a stroke.

Research studies have provided evidence for the connection between hypothyroidism and stroke. A study published in the journal Stroke examined the association between overt hypothyroidism, atherosclerotic risk factors, and stroke. Another study in the NCBI database investigated the alteration of thyroid hormones in patients with ischemic stroke and found an increased risk associated with subclinical hypothyroidism, particularly in those under 65 years of age and with higher TSH levels. Additionally, postmenopausal women with subclinical hypothyroidism may also be at a higher risk of ischemic stroke. These findings highlight the impact of hypothyroidism on stroke risk and the importance of managing thyroid hormone levels to maintain cardiovascular health.

On the other hand, hyperthyroidism, or the overproduction of thyroid hormones, is also associated with an increased risk of stroke. Hyperthyroidism is linked to atrial fibrillation, which is a common cause of cardioembolic stroke. Atrial fibrillation is an irregular heart rhythm that can lead to the formation of blood clots, which can then travel to the brain and cause a blockage, resulting in an ischemic stroke. Additionally, hyperthyroidism may be associated with acute cerebral venous thrombosis, Moyamoya disease, and Giant cell arteritis, although further studies are needed to establish definitive evidence.

Stroke Patients: Occupancy in Hospitals

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Thyroid hormones and functional outcomes after ischemic stroke

Stroke is the fifth leading cause of death and the primary cause of long-term adult disability in the United States. Increasing evidence suggests that low T3 levels immediately following acute ischemic stroke are associated with greater stroke severity, higher mortality rates, and poorer functional outcomes.

Study setting and population

This study was conducted at an 868-bed community-based teaching hospital with a Neurology Residency Program. This center has The Joint Commission's Gold Seal of Approval and the American Heart Association's Advanced certification as a comprehensive stroke center and has an annual stroke admission rate of approximately 1000. This study was approved by the Institutional Review Board.

Blood collection

Blood was collected from patients over 18 years of age with radiologically confirmed acute ischemic stroke (n = 129) at 24 ± 6 h post-symptom onset under an approved IRB from December 2011 to May 2013. Patients with active malignancy or treatment with immunosuppressants were excluded from the study. Serum levels of TSH, free T3, and free T4 were quantified by solid-phase chemiluminescent immunometric assay (R&D Systems, Minneapolis, MN).

Statistical analysis

Continuous data, such as age, are presented as means (standard deviation). Non-normally distributed continuous and ordinal data are presented as medians (interquartile range) and were analyzed with non-parametric tests (Spearman’s Rho). Categorical data are presented as proportions, and group differences were assessed with chi-square tests of proportion. Several variables with non-normal distributions were dichotomized and analyzed with chi-square tests of proportions.

Results

Lower levels of free T3 were associated with worse prognosis at hospital discharge, and at 3 and 12 months post-stroke, however, these associations diminished after correction for other known predictors of stroke outcome. Thyroid hormones have a complex relationship with ischemic stroke and stroke recovery, which merits further larger investigations.

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Hyperthyroidism and hypothyroidism can lead to atherosclerosis

Hyperthyroidism, a condition in which the thyroid gland produces too much thyroid hormone, has been linked to increased heart rate and pulse pressure, which can affect arterial stiffness and contribute to atherosclerosis. Additionally, hyperthyroidism can cause atrial fibrillation, a common cause of cardioembolic stroke.

On the other hand, hypothyroidism, characterised by insufficient thyroid hormone production, is associated with several traditional and emerging risk factors for atherosclerosis. These include hypertension, high levels of low-density lipoprotein cholesterol, low-grade inflammation, and hypercoagulability. Hypothyroidism can also lead to structural changes in the arterial wall, such as increased collagen expression and impaired endothelial function, which can further contribute to atherosclerosis.

While the exact mechanisms underlying the relationship between thyroid dysfunction and atherosclerosis are not fully understood, it is clear that thyroid dysfunction can increase the risk of cardiovascular events, including strokes. Therefore, identifying and managing thyroid disorders is crucial for reducing the risk of atherosclerosis and its associated complications.

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Hypothyroidism is a common co-morbidity in patients with acute ischemic stroke

Hypothyroidism is a condition where the thyroid gland does not produce enough thyroid hormones. It is linked to altered lipid metabolism and is associated with hyperhomocysteinemia. Acute ischemic stroke, on the other hand, is a sudden onset of focal neurological deficits within a vascular territory stemming from underlying cerebrovascular pathologies. It is the most common type of stroke, constituting about 87% of all strokes.

The Link Between Hypothyroidism and Acute Ischemic Stroke

Several studies have established a link between hypothyroidism and acute ischemic stroke. In a study by Remmel et al. (2006), 12% of patients with acute ischemic stroke or transient ischemic attack (TIA) had hypothyroidism. Similarly, a study by Bashyal et al. (2021) found that 17.8% of patients with ischemic stroke had altered thyroid levels, with 15.1% being hypothyroid.

The Role of Thyroid Hormones in Stroke

Thyroid hormones play a crucial role in the body's response to acute ischemic stroke. Low levels of free T3 (fT3) have been associated with greater stroke severity, higher mortality rates, and poorer functional outcomes. Additionally, patients with low TSH levels had significantly higher in-hospital mortality.

Risk Factors and Comorbidities

It is important to note that hypothyroidism is a risk factor for stroke and is associated with several traditional and newer atherosclerotic risk factors, especially hypertension, hyperlipidemia, and hyperhomocysteinemia. Other comorbidities that have been linked to increased mortality in acute stroke patients include atrial fibrillation, cigarette smoking, alcohol consumption, and diabetes.

Treatment and Management

The treatment and management of acute ischemic stroke aim to preserve tissue in areas with decreased blood flow by restoring blood flow and improving collateral circulation. Recanalization strategies include intravenous recombinant tissue-type plasminogen activator and mechanical thrombectomy. Early intervention is crucial, as the principle of "time is brain" underscores the importance of timely revascularization to minimize long-term sequelae.

In conclusion, hypothyroidism is a common co-morbidity in patients with acute ischemic stroke. The link between the two conditions is supported by multiple studies that have found an association between altered thyroid levels and acute ischemic stroke. The presence of hypothyroidism may represent a modifiable stroke risk factor, and prospective studies are needed to verify this association further.

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Hypothyroidism can increase the risk of heart disease

Hypothyroidism, or an underactive thyroid, is when the thyroid does not produce enough thyroid hormone. Thyroid hormones affect nearly every organ in the body, especially the heart. Hypothyroidism can cause a range of symptoms, including fatigue, weight gain, cold intolerance, constipation, and dry skin. However, these symptoms are common in people as they age, even those with normal thyroid levels. In fact, more than half of people with normal thyroid function experience hypothyroidism symptoms.

In addition, hypothyroidism can cause diastolic dysfunction, where the heart muscle cannot fully relax after each heartbeat, leading to stiffening of the heart's pumping chambers. This can eventually result in heart failure. Hypothyroidism also causes blood vessels to stiffen, which can lead to high blood pressure or hypertension.

Other cardiac symptoms associated with hypothyroidism include swelling or edema, heart arrhythmias, heart palpitations, shortness of breath or dyspnea, and slow heart rate or bradycardia. Hypothyroidism can also worsen coronary artery disease by increasing LDL cholesterol and C-reactive protein levels. Therefore, it is important for individuals experiencing any of these symptoms to get their thyroid hormone levels checked, especially if they already have heart disease.

Frequently asked questions

Yes, thyroid issues can lead to a stroke. Hypothyroidism can cause hypertension, hypercholesterolemia, cardiac dysfunction, and both hypo- and hypercoagulability, all of which are risk factors for stroke. Hyperthyroidism is associated with atrial fibrillation, which is a common cause of cardioembolic stroke.

Risk factors for thyroid-related strokes include hyperthyroidism, hypothyroidism, hyperhomocysteinemia, and hypercoagulability.

To prevent a thyroid-related stroke, it is important to identify and manage any thyroid issues early on. This may involve thyroid hormone replacement therapy or, in the case of hyperthyroidism, anticoagulant therapy.

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