- A study conducted
in Netherlands looks at the association between thyroid hormone levels and
sudden cardiac death.
- 261 sudden
cardiac deaths were analyzed.
- Thyroid hormone
level was found to increase the risk of sudden cardiac death by 2.5 times.
- The risk levels
remained high even after controlling for other risk factors for cardiac
death like high blood pressure (hypertension) and high cholesterol.
A sudden cardiac death
due to loss of
cardiac function was found to be significantly more in people with high levels
of thyroid hormone than in people with lower levels. Sudden cardiac death is
the cause of more than half of cardiovascular disease associated death and it
occurs when there is a malfunction in the heart's electrical rhythm.
Senior author of the study Dr. Layal
Chaker from the Netherland's Erasmus University Medical Center Rotterdam says
"Currently, we do not have a good way to predict sudden cardiac death in
the general population. Thus identifying additional risk factors is crucial.
Our results indicate that thyroid hormone levels may be useful for assessing
risk to prevent sudden cardiac death."
‘Elevated thyroid hormone levels could signal for sudden cardiac death.’
secreted by the thyroid gland that is present at the base of the throat and it
is important for the proper functioning of every organ system in the body
including the heart and the brain. When the thyroid hormone makes very little
hormone, it is called hypothyroidism.
of the Thyroid Hormone on the Heart
The thyroid hormone is
known to exert an influence on the functioning of the heart by
- Affecting the force and the rate at which the heart
- Cholesterol level
- Blood pressure
As these crucial
parameters are influenced by the thyroid hormone, a problem with the level of
thyroid hormone can lead to the development of heart disease or it could make
an existing heart condition worse.
Hypothyroidism and the Heart
is a condition in which there
is lower production of the thyroid hormone. It can lead to the following
effects on the heart
- Lowered heart rate
- The artery walls become less elastic
- Increase in blood pressure
- A build up of cholesterol
is a condition in which
there is excess secretion of thyroid hormone in the blood. This condition is
very rare and is found to affect only 1% of the population.
Hyperthyroidism can lead
to the following symptoms
- The heart beat is faster
- May lead to abnormal heart rhythms
- Can lead to atrial fibrillation
Though the connection
between the thyroid hormone and the heart have been established before by
numerous studies, this study by Dr Layal Chaker and colleagues finds a
connection between irregular secretion of the thyroid hormone and sudden
The Rotterdam study
involved a long term finding that delved into the reasons behind heart and
other chronic diseases among the elderly people living in the Netherlands. The
average age of people who undertook the study was 65 years and they were mostly
Caucasians. Women constituted more than half of the study population.
Study that Links Thyroid Hormone and Cardiac
Dr Layal Chaker and
colleagues studied 10,318 patients who were part of the Rotterdam Study. The
death certificates and medical records of patients who died due to sudden
cardiac death were analyzed and the level of free thyroxine thyroid hormone levels and the
thyroid stimulating hormone in the blood samples
of the Study
The researchers found
that 261 study participants died of sudden cardiac death, stressing the
prevalence of this condition.
- It was found that free thyroxine hormone levels in the
blood that was at the higher end of the normal range was 2.5 times more
likely to lead to sudden cardiac death than levels of the hormone at the
lower end of the normal range.
- Higher levels of free thyroxine hormone lead to 4 times
increase in 10 year risk for sudden cardiac death when compared to low
levels of the hormone.
- The high risk for sudden cardiac death due to high
thyroxine hormone remained the same even after controlling for other
factors like high blood pressure and high cholesterol.
The study shows that
elevated levels of thyroxine hormone could increase the risk
of sudden cardiac death
, which makes it imperative to test for levels
of the thyroid hormone in the blood. It is important to understand the risk
factors for abnormal thyroid hormone levels and they include:
Factors: The condition could run in the
family with people who are first relatives with an affected individual at
a higher risk for the disease.
- Age is another important factor, as the age advances, the
risk of thyroid problem also increases.
- Gender: It has been found that women are far more likely to
be affected by a thyroid problem than men.
Conditions: There are certain medical
conditions which can trigger a thyroid hormone problem like type 1
diabetes, pernicious anemia and Addison's disease.
It is important to treat
high levels of thyroid hormone in the blood to control the risk of sudden
cardiac death. The study also raises awareness about the risk associated with
hormone replacement therapy as detailed by Dr. Layal Chaker "We know that
a considerable proportion of patients on thyroid hormone replacement therapy
are over-treated and so have high blood levels of thyroid hormone. Our study
suggests more caution is warranted in the treatment of thyroid hormone
replacement. Replacement therapy is often aimed at the high normal range which
carries a risk of overtreatment."
The study provides a
connection between elevated thyroid hormone levels and sudden cardiac death but
the researchers highlight that further research may be required to understand
if other factors were involved. The thyroid hormone levels were tested at a
particular point in the study and this level could have increased or decreased
after the testing.
Sudden cardiac deaths
display very few symptoms prior to the event and this study offers an insight
into a possible mechanism that could lead to it, providing scope for better
- Hypothyroidism and Heart Disease - (http://www.hormone.org/questions-and-answers/2013/hypothyroidism-and-heart-disease)
- Thyroid Disease and Heart - (http://circ.ahajournals.org/content/116/15/1725)
- Thyroid Hormone: How it affects your heart? - (http://www.health.harvard.edu/heart-health/thyroid-hormone-how-it-affects-your-heart)