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Hyperthyroidism

Humza Khizer

Overview

Hyperthyroidism is an overactive state of the thyroid gland in which the gland produces and releases thyroid hormones in excess.

The thyroid is a small butterfly-shaped gland with 2 lobes on either side of the trachea (windpipe), situated in front of the neck<a href="#accordion">[1][2]</a>.&nbsp;It produces 2 hormones namely thyroxine (T3) and triiodothyronine (T4) and these hormones control the body&#39;s metabolism. Metabolism is the process of converting food into energy so that it can be utilized by the cells for day-to-day functioning.&nbsp;&nbsp;

All the organs of the body are interlinked with the thyroid gland and are, therefore, influenced by any fluctuation in the levels of the thyroid hormone. The increase in levels of thyroid hormones (as seen in hyperthyroidism) causes the body&#39;s metabolism to accelerate, producing a myriad of signs and symptoms such as rapid weight loss, irregular heartbeat, anxiety, and increased appetite.

There are multiple options to treat hyperthyroidism, including medications, surgery, and radiation<a href="#accordion">[3]</a>. Although hyperthyroidism is a treatable condition, it can result in deleterious health outcomes if the symptoms are ignored for too long.&nbsp;

The prevalence rate of hyperthyroidism is 0.8% in the United States and 1.3% in Europe<a href="#accordion">[4]</a>. According to a report, 1 in 100 people in the United States who are older than 12 years of age has hyperthyroidism<a href="#accordion">[5]</a>. Women are generally more predisposed to thyroid disorders than men and are 10 times more likely to develop an overactive thyroid as compared to men. Women between the age group of 20-40 years are more likely to develop hyperthyroidism<a href="#accordion">[2]</a>.

Moreover, a large-scale study conducted in Norway in 2007, interestingly found that smokers had higher levels of thyroid hormones as compared to non-smokers. Additionally, hyperthyroidism was twice as prevalent in women who smoked in contrast to women who did not<a href="#accordion">[6]</a>.

Hyperthyroidism is quite prevalent in Pakistan since 5.1% and 5.8% of the population are reported to have hyperthyroidism and subclinical hyperthyroidism respectively. Females are predominantly affected by both these conditions<a href="#accordion">[7]</a>. 
&nbsp;

Hyperthyroidism can develop in many forms due to different conditions, including:

&nbsp;

<ul>
	<li>
	<h5>Graves&rsquo; Disease</h5>
	</li>
</ul>

Graves&rsquo; disease, also known as diffuse toxic goiter, is considered as the leading cause of hyperthyroidism. It is an immune system disorder, i.e., the antibodies act against an individual&#39;s own healthy cells. In Graves&rsquo; disease, the thyroid gland is attacked by self-antigens, which results in overproduction of the thyroid hormones.&nbsp;

It&rsquo;s not known what exactly triggers Grave&rsquo;s disease, but researchers believe that genetic and environmental factors are the root causes of this condition; with genetic components making a greater contribution to the development of this disease.

&nbsp;

Graves&rsquo; disease presents with the following features<a href="#accordion">[8]</a>:

1. Goiter (enlarged thyroid gland resulting in a swollen neck)

2. Exophthalmos (protruding or bulging eyes)

3. Thickened skin in the shin area of the leg&nbsp; 
&nbsp;

<ul>
	<li>
	<h5>Multinodular Goiter&nbsp;</h5>
	</li>
</ul>

Multinodular goiter is also known as toxic nodular goiter or Plummer&#39;s disease. The thyroid has multiple nodules or benign growths (adenomas) in this condition and they become increasingly active in releasing thyroid hormones, resulting in hyperthyroidism.

The cause behind multinodular goiter is not known. Unlike Graves&rsquo; disease, this form of hyperthyroidism does not present with exophthalmos or skin problems<a href="#accordion">[8]</a>. 
&nbsp;

<ul>
	<li>
	<h5>Thyroiditis</h5>
	</li>
</ul>

Thyroiditis refers to the inflammation of the thyroid gland. In this condition, excessive amounts of thyroid hormones leak into the blood, resulting in a temporary state of hyperthyroidism followed by hypothyroidism<a href="#accordion">[8]</a>.

Thyroiditis can be after a bacterial or viral infection or it can be due to an autoimmune condition. It is also seen after pregnancy when the thyroid gland gets inflamed. Some types of thyroiditis might be painful while others are not<a href="#accordion">[3]</a>.

Lastly, when individuals consume a lot of thyroid medications, it results in a hyperthyroid state called &ldquo;thyrotoxicosis&rdquo;<a href="#accordion">[8]</a>.

&nbsp;

Signs And Symptoms

Hyperthyroidism presents with a wide variety of signs and symptoms that overlap with other health conditions and make it tricky for the physician to diagnose the condition<a href="#accordion">[1][3]</a>: 
&nbsp;

<ul>
	<li>Sudden unexplained weight loss despite an increase in appetite&nbsp;</li>
	<li>Tachycardia, i.e., an&nbsp;increased heart rate of more than 100 beats per minute</li>
	<li>Arrhythmia or irregular heart rate&nbsp;</li>
	<li>Palpitations or&nbsp;pounding heart</li>
	<li>Tremors or trembling of hands and fingers&nbsp;</li>
	<li>Nervousness</li>
	<li><a href="https://www.merisehat.pk/disease/anxiety" target="_blank">Anxiety</a></li>
	<li>Irritability</li>
	<li>Diarrhea</li>
	<li>Changes in vision</li>
	<li>Irregularities in menstrual pattern</li>
	<li>Goiter, which is an enlarged thyroid gland resulting in a swollen neck</li>
	<li>Lack of tolerance to heat</li>
	<li>Increased sweating</li>
	<li>Change in hair texture as the hair becomes brittle&nbsp;</li>
	<li>Skin becomes thin, moist, and warm</li>
	<li>Fatigue</li>
	<li>Difficulty sleeping</li>
	<li>Muscle weakness</li>
</ul>

&nbsp;

Causes

There are various reasons for hyperthyroidism. However, in most cases, it occurs due to genetic factors. The following result in an overactive thyroid:

&nbsp;

<ul>
	<li>Grave&rsquo;s Disease - Every 3 out of 4 people with hyperthyroidism have Graves&rsquo; disease as the underlying cause<a href="#accordion">[2]</a>. It is the most common condition causing hyperthyroidism.&nbsp; 
	&nbsp;</li>
	<li>Thyroid Nodules And Benign Adenoma - Conditions such as toxic multinodular goiter and thyroid adenomas result in hyperthyroidism. People over the age of 60 years are more likely to develop thyroid nodules<a href="#accordion">[2]</a>. 
	&nbsp;</li>
	<li>Thyroid Cancer - Although rare, cancer of the thyroid gland results in overproduction of the thyroid hormones. 
	&nbsp;</li>
	<li>Medications - Certain medications, such as amiodarone which is used to treat arrhythmia, have increased iodine content. They can be responsible for thyroid overactivity as well<a href="#accordion">[2]</a>. 
	&nbsp;</li>
</ul>

In order to evaluate a thyroid disorder before the disease becomes clinically apparent, a screening test is performed.&nbsp;Thyroid screening tests consist of taking a blood sample and sending it to the laboratory to check the levels of TSH, T3, and T4. Out of all the hormones, TSH levels are the most ideal marker to indicate the presence of any thyroid disorders. Any fluctuation in the TSH levels is the earliest indicator of thyroid disease since T3 and T4 are normal in subclinical diseases. If the TSH levels are lower than normal then it indicates hyperthyroidism<a href="#accordion">[9]</a>.

&nbsp;

Diagnosis

To diagnose hyperthyroidism, your doctor would start with taking your history and&nbsp; performing a physical exam and then proceeding to further investigations. 
&nbsp;

<ul>
	<li>
	<h5>History And Physical Exam</h5>
	</li>
</ul>

Your doctor will take a detailed history of your condition; asking about your symptoms and how long you have been experiencing them.&nbsp;It is followed by a physical exam wherein your doctor inspects and feels your thyroid for enlargement or nodularity, and auscultates for vascularity.&nbsp;

Next, they will examine your hands to look for tremors, check your pulse, and feel the temperature of your skin along with inspecting other signs of the disease<a href="#accordion">[10][11]</a>. 
&nbsp;

<ul>
	<li>
	<h5>Blood Tests</h5>
	</li>
</ul>

Blood tests are integral to diagnosing hyperthyroidism. A blood sample is taken and sent to a laboratory. The point is to evaluate the levels of different hormones in the blood, including T4 and T3 which are the thyroid hormones, and TSH which is the hormone released by the pituitary gland. TSH is directly responsible for controlling the levels of T3 and T4 in the blood. If you have increased levels of T3 and T4 and less than normal levels of TSH, then this depicts a hyperthyroid state<a href="#accordion">[10]</a>. 
&nbsp;

Once a diagnosis of hyperthyroidism is made, further investigations are carried out to evaluate the root cause of hyperthyroidism: 
&nbsp;

<ul>
	<li>
	<h5>Radioiodine Uptake Test</h5>
	</li>
</ul>

In this test, you are given a small dose of radioactive iodine which is to be taken orally. The aim of the test is to find out how much iodine is taken up by the thyroid gland. You will be evaluated after a period of 4, 6, or 24 hours to see the quantity of iodine taken up by the thyroid gland<a href="#accordion">[10]</a>.

If the results show a high uptake of radioactive iodine, it indicates that the thyroid is overproducing thyroxine (T4). In this setting, the likely cause is either Graves&rsquo; disease or thyroid nodules that are over-functioning.&nbsp;

In contrast, if the T3 and T4 levels are high but radioactive iodine uptake is low, it indicates thyroiditis since the gland itself is not overproducing the thyroid hormones and the leakage of hormones into the blood is due to inflammation.&nbsp; 
&nbsp;

<ul>
	<li>
	<h5>Thyroid Scan&nbsp;</h5>
	</li>
</ul>

An extension of the radioiodine uptake test is a thyroid scan, which involves imaging your thyroid gland after radioactive iodine uptake. A special camera takes images of the gland showing how much iodine is accumulated within the thyroid gland<a href="#accordion">[10]</a>.&nbsp;&nbsp; 
&nbsp;

<ul>
	<li>
	<h5>Thyroid Ultrasound&nbsp;</h5>
	</li>
</ul>

An ultrasound uses high-frequency sound waves to get images of the thyroid gland. It is a better technique to detect thyroid nodules as compared to other tests. Moreover, the benefit of ultrasound is that it does not involve any exposure to radiation<a href="#accordion">[10]</a>.

&nbsp;

Treatment

There are multiple treatment options to treat hyperthyroidism. But it all depends on your age, your physical health, and the cause of hyperthyroidism.&nbsp;

Your doctor will decide which of the following is the most suitable approach to treat hyperthyroidism: 
&nbsp;

<ul>
	<li>
	<h5>Radioactive Iodine&nbsp;</h5>
	</li>
</ul>

You will be asked to consume it orally. Once the radioactive iodine gets absorbed in the thyroid gland, it will cause it to shrink. It is an effective treatment for hyperthyroidism as it damages the overactive thyroid tissues.&nbsp;

However, people who receive this treatment develop hypothyroidism due to the destruction of the parenchyma of the gland, and then thyroid hormone replacement therapy is needed to ensure normal levels of thyroid hormones in the blood<a href="#accordion">[10]</a>. 
&nbsp;

<ul>
	<li>
	<h5>Medications&nbsp;</h5>
	</li>
</ul>

Anti-thyroid medications work by counteracting the production of thyroid hormones. The most commonly used medications to treat this condition are called thioamides and include methimazole (MMI) and propylthiouracil (PTU)<a href="#accordion">[6]</a>.

It takes anywhere from several weeks to several months for symptoms to start improving after taking anti-thyroid medications. For most people, these medications become a long-term solution to treat the condition effectively while some people have reported that they experienced relapses after using anti-thyroid medications.&nbsp;

Both PTU and MMI have adverse effect profiles and are known to cause serious liver damage, which is life-threatening. PTU, in particular, is linked to a greater degree of liver damage hence it is reserved for patients who can&#39;t tolerate methimazole<a href="#accordion">[10]</a>.

Few people also develop allergies to anti-thyroid medications and this results in skin rash, fever, joint pain, or hives.&nbsp; 
&nbsp;

<ul>
	<li>
	<h5>Beta-Blockers&nbsp;</h5>
	</li>
</ul>

Beta-blockers are not a definitive treatment of hyperthyroidism and shouldn&#39;t be used as the sole therapy to manage the condition. It is a medication used to control the symptoms of hyperthyroidism such as palpitations, tremors, and a rapid heart rate.&nbsp;

Note: It is not recommended for individuals who have asthma.&nbsp;Besides, beta blockers are known to cause sexual dysfunction and fatigue<a href="#accordion">[10]</a>. 
&nbsp;

<ul>
	<li>
	<h5>Thyroidectomy&nbsp;</h5>
	</li>
</ul>

Thyroidectomy is a surgical procedure to remove some part or whole of the thyroid gland. Individuals who cannot tolerate anti-thyroid medications and don&#39;t want to take the risk of radioactive iodine therapy usually opt for surgical treatment to treat their overactive thyroid gland.&nbsp;

Generally, the surgery is quite safe but there is a risk of getting your vocal cords or parathyroid glands damaged in the process.&nbsp;Moreover, since the complete or partial thyroid gland is removed, synthetic thyroid hormones are taken to achieve the natural level of these hormones in the blood<a href="#accordion">[10]</a>.

&nbsp;

&nbsp;Hyperthyroidism, if untreated, results in a host of complications<a href="#accordion">[3]</a>: 
&nbsp;

<ul>
	<li>Heart Problems - One of the most worrisome complications of hyperthyroidism is the development of heart problems, such as an abnormal rhythm pattern known as atrial fibrillation. Atrial fibrillation is associated with an increased risk of <a href="https://www.merisehat.pk/disease/stroke" target="_blank">stroke </a>and also leads to congestive heart failure.&nbsp; 
	&nbsp;</li>
	<li>Eye Problems - Hyperthyroid individuals can develop a condition called Graves&#39; ophthalmopathy. It results in red and swollen eyes that are bulging and causing double and blurry vision, and increased sensitivity to light. 
	&nbsp;</li>
	<li>Brittle Bones - The thyroid gland also controls the calcium metabolism and incorporation of the mineral into the bones. So, when thyroid hormones are in excess, it causes osteoporosis or a lack of calcium deposition in the bones. As a result, the individual develops brittle and weak bones.&nbsp; 
	&nbsp;</li>
	<li>Skin Disorders&nbsp;- In rare cases of hyperthyroidism, Graves&#39; dermopathy develops which is a condition characterized by red, swollen skin on the shins and feet. 
	&nbsp;</li>
	<li>Thyroid Storm&nbsp;- It is also referred to as thyrotoxic crisis and it is a condition when the symptoms of an overactive thyroid are intensified. It is a medical emergency; the patient reports a rapid pulse, delirium, and fever.&nbsp;</li>
</ul>

&nbsp;

The following risk factors are associated with hyperthyroidism<a href="#accordion">[3]</a>:

<ul>
	<li>Female gender</li>
	<li>Family history of thyroid disorders, particularly Graves&#39; disease&nbsp;</li>
	<li>History of a chronic disease such as type 1 diabetes, primary adrenal insufficiency, and pernicious <a href="https://www.merisehat.pk/disease/anemia" target="_blank">anemia&nbsp;</a></li>
</ul>

&nbsp;

Hyperthyroidism is a state of overactivity of the thyroid gland and the most common cause of this condition &ndash; the Graves&rsquo; Disease &ndash; has an autoimmune basis the reason of which is not known. It has been linked with genetic and environmental factors but the exact cause isn&#39;t determined. Hence measures to prevent thyroid disorders such as hyperthyroidism and hypothyroidism are not known.&nbsp;

However, consuming too much iodine in your food can result in the development of an overactive thyroid gland and can worsen hyperthyroidism if you are already diagnosed with the condition. You should take iodine-fortified food cautiously and should not incorporate them excessively in the diet as this can result in a hyperthyroid state<a href="#accordion">[1]</a>.

&nbsp;

Neonatal hyperthyroidism is a rare but potentially fatal condition if not diagnosed and treated by an endocrinologist (doctors who specialize in the diseases of endocrine glands). It develops in babies if the mothers have had Graves&#39; disease either during pregnancy or even if they were treated for it before pregnancy. Newborns with hyperthyroidism are then at risk of developing life-threatening neonatal thyrotoxicosis. One way to prevent this condition from developing is screening<a href="#accordion">[12]</a>.&nbsp;

Screening can prevent neonates from developing cardiac complications of neonatal hyperthyroidism<a href="#accordion">[13]</a>.&nbsp;Neonates are generally screened for hypothyroidism but not hyperthyroidism. However, the screening which uses blood samples from the newborn on the 3rd day of birth to measure TSH levels can also be used to detect hyperthyroidism.&nbsp;

Subsequently, it has been evaluated through a study that earlier diagnosis of neonatal hyperthyroidism in infants will help endocrinologists to initiate treatment before the disease becomes overt and ensure improved outcomes<a href="#accordion">[13]</a>.&nbsp;

&nbsp;

Key Points

<ul>
	<li>Hyperthyroidism is a state of overactivity of the thyroid gland.&nbsp;</li>
	<li>It is a rare condition that results in increased levels of thyroid hormones.</li>
	<li>Hyperthyroidism causes a hyper metabolic state of the body and presents with rapid heartbeat, palpitations, sudden weight loss, and increase in appetite.&nbsp;</li>
	<li>An overactive thyroid gland can be due to multiple etiologies such as Graves&#39; disease, thyroid nodules, and thyroiditis.&nbsp;</li>
	<li>Graves&#39; disease is the most common cause of hyperthyroidism.</li>
	<li>Hyperthyroidism is a manageable condition and it can be treated through medications, radioactive iodine therapy, and surgery.&nbsp;</li>
</ul>

&nbsp;