When a thyroid disorder arises the effect on the body can be catastrophic. Part of the endocrine system, the thyroid gland is the largest in the neck lying to the front, just below the muscle and skin. An integral part of the body’s functioning, the thyroid gland is something that most of us rarely, if ever consider.
Here’s a closer look at the thyroid gland and its function as well as everything you need to know about thyroid disorders.
Before looking at the things that can go wrong, it’s worthwhile to briefly cover exactly what the thyroid gland is, and the role it plays within the body.
We already know that it’s situated in the front of the neck, sitting just under your Adam’s apple. It has two lobes which are both roughly the size of half a plum which lie on either side of the windpipe.
These lobes are a butterfly shape with a center strip of tissue joining the two parts. The isthmus is the name for this middle section. Very occasionally the isthmus isn’t present, simply the two lobes of the thyroid.
The thyroid gland is part of the endocrine system and it releases two hormones into the blood: T3 and T4. These are essential hormones which are required for the body to work efficiently. The thyroid is able to produce these hormones by extracting iodine from the blood.
The thyroid also produces Calcitonin; this substance plays a role in controlling the amount of calcium in the blood.
Another name for T4 is thyroxine and it contains four iodine atoms. T3 is triiodothyronine and contains three iodine atoms. The cells of the body convert the T4 into T3; this is necessary because it’s T3 which is the biologically active hormone. Without the presence of T3, there would be no effect on the body so it’s essential for the thyroid to release both. (1)
The thyroid hormones determine how quickly the cells in the body work; this is what you know as your metabolism. If there’s an excess of thyroid hormones, the body works too quickly and is called hyperthyroidism. If you don’t have enough thyroid hormones in your body, the functions slow right down. This is hypothyroidism.
Even if you don’t have either hyperthyroidism or hypothyroidism (types of thyroid disorders), your thyroid gland may work at a different speed to another person’s. This is what is often referred to as having a fast or slow metabolism.
The balance of thyroid hormone levels in the body requires a very delicate balance; too much or too little can lead to thyroid disorders (more about that below).
T4 and T3 are produced by drawing on the iodine in the blood system. The cells in the thyroid gland are the only ones capable of using iodine in this way. The amount of iodine in the body determines how much T3 and T4 can be produced. (2)
However, the thyroid doesn’t just flood the body with hormones because it can; production is carefully controlled the pituitary gland. In turn, the hypothalamus regulates the pituitary gland.
Think of as a three step process, akin to turning on the thermostat in your home. The hypothalamus is you, deciding the level of the thermostat. The pituitary gland acts as the thermostat, detecting when the heat is at the right levels and switching the thermostat on and off.
The thyroid gland is the furnace in this analogy, releasing heat ie/thyroid hormones, when switched on by the thermostat.
The hypothalamus is in the brain and sends TSH Releasing Hormone (TRH) which triggers the pituitary gland. The pituitary gland is around the size of a peanut and located between the hypothalamus and the thyroid gland, nestling at the base of the brain.
In response to TRH being released, the pituitary gland produces Thyroid Stimulating Hormone (TSH) which is sensed by the thyroid gland and in turn, it released more T3 and T4. If any step in the process breaks or performs abnormally it can lead to thyroid problems. (3)
There is a complex mechanism behind the production of thyroid hormones and the thyroid gland plays a big part. It is critical that every step works exactly as it should because the effects of a dysfunctional thyroid can be far-reaching and lead to thyroid disorders.
To put that into perspective, it’s helpful to understand that the thyroid gland helps to regulate all of these bodily functions:
- Heart rate
- Peripheral and central nervous system
- Muscle strength
- Body weight
- Menstrual cycle
- Body temperature
If your thyroid isn’t working properly, there could be a profound effect on any or all of the above. (4)
For example, too much T3/T4 could lead to your heart beating too fast and diarrhoea while too little could cause a slowed heart rate and constipation.
There’s not one single test for all thyroid disorders because of the complex chain which has to occur to enable healthy function. Understanding the physiology of the endocrine system and how the hypothalamus, pituitary and thyroid all work together is essential in pinpointing any potential thyroid disorder.
If doctors suspect a problem with the function of the thyroid it’s a matter of establishing where in the chain the issue is occurring. For example, low levels of T4 in the blood could mean that the thyroid gland isn’t responding to TSH or it could be a fault right at the start of the process with the hypothalamus.
However, if you test the blood and there are high levels of TSH but low levels of T4, you know that the hypothalamus and pituitary are doing their jobs but the thyroid isn’t responding. In practice, it’s usually the pituitary or the thyroid gland which has the problem.
Thyroid tests are extremely accurate so when you combine a couple of different types of tests together, it’s possible to figure out where the abnormality, leading to thyroid disorder, is arising from. (5)
Here are some of the most common types of thyroid test:
Serum (blood) thyroid function tests
Blood tests are the most common form of thyroid function tests and are quick and easy to do. Thyroid function serum tests are helpful for both diagnosis and management, allowing doctors to monitor the level of thyroid hormones in the blood.
In most cases, the blood test checks for TSH, Free T3 and Free T4. The “Free” hormones refers to the active elements of T3 and T4. If you don’t yet have a diagnosis, your doctor may also check for thyroid antibodies as this helps to rule out specific causes. For those with thyroid cancer, blood tests may include checks for thyroglobulin and calcitonin for monitoring purposes.
Every laboratory has a different reference range but there are some guidelines to the approximate values of a healthy person. The specific combination of results can help aid a diagnosis:
- Raised TSH with low Free T4 – hypothyroidism
- Low TSH with raised Free T4 and Free T3 – hyperthyroidism
- Low TSH with low Free T4 – potentially a pituitary disorder
Iodine uptake scan
The thyroid gland uses iodine to manufacture thyroid hormones so measuring the amount it absorbs is a measure of how it’s functioning. An iodine uptake scan involves a patient receiving a dose of radioactive iodine on an empty stomach and then scanning the thyroid to see how much is absorbed for use.
Various factors may affect the result so it’s typically used in conjunction with blood tests to get a complete picture.
Different to an iodine uptake scan, a thyroid scan also uses radioactive iodine. The scan provides a “picture” of the thyroid, including any nodules which are present. It can also help to differentiate between cold and hot nodules. Hot nodules produce thyroid hormones and are rarely cancerous.
A cold nodule may be cancerous or benign. Following the scan, a specialized test – a needle biopsy – can be performed to ascertain the nature of the nodule, if required.
Here’s a closer look at some of the most commonly seen disorders and diseases:
Hyperthyroidism is a common thyroid disorder of the thyroid gland and is caused when the thyroid is working too hard and producing too many hormones. The symptoms you might notice with hyperthyroidism include:
- Racing heart
- Mood swings
- Difficulty tolerating heat
- Muscle fatigue or weakness
- Difficulty sleeping (a change in your normal pattern)
- Weight loss
- Frequent bowel movements
- Light or absent periods
- Bulging eyes
The thyroid gland can also enlarge with all the additional work and become visibly swollen at the front of the neck. This is a goitre. (6)
There can be many causes for hyperthyroidism so it’s important to identify if there’s any significant underlying disease. Common causes are inflammation of the thyroid gland, thyroiditis, and having nodules on the thyroid gland. Both of these conditions trigger the thyroid to go into overdrive, producing too much T3 and T4. (7)
Consuming too much iodine is another cause of hyperthyroidism, either through the diet or because of medication.
Medication can be prescribed that interferes with thyroid hormones, reducing the amount produced. Radioactive iodine therapy can also be offered; this damages the cells that produce the hormones. If neither of these options produce the desired outcome, surgery to remove part of the thyroid can be performed. (8)
The exact treatment depends on a number of factors including age, severity of symptoms and any underlying cause.Your doctor may also prescribe additional medication such as beta blockers to ease symptoms such as fast heartbeat.
Uncontrolled hyperthyroidism isn’t just uncomfortable, it can also be dangerous which is why diagnosis and treatment is important. Left unchecked, hyperthyroidism can lead to heart abnormalities which can be fatal, such as sudden cardiac arrest and congestive heart failure.
The good news is that there is no reason for treatment not to be a success. It can take a while to reach the right balance but it’s ultimately achievable.
In the exact opposite to hyperthyroidism, hypothyroidism is when there isn’t enough thyroid hormones circulating in the body. Hypothyroidism is common, particularly in women. It’s estimated that around 10% of all females have some level of hypothyroidism.
Some of the symptoms of hypothyroidism are quite vague, making them hard to pinpoint. These are the signs to look out for:
- Gaining weight
- Difficulty losing weight while dieting
- Dry, rough hair
- Pale, coarse skin
- Unable to tolerate cold temperatures
- Hair loss
- Muscular aches and cramps
- Memory loss
- Reduced libido
- Menstrual cycle changes
You may experience some or all of the above symptoms, depending on the level of the deficiency. (9)
The most common causes of an underactive thyroid gland are:
- Underlying disease such as Hashimoto’s
- Medication for other conditions
- Birth defect
- Dietary intake eg/kelp
- Excessive dose of hyperthyroidism medication
- Surgery or radioactive treatment for hyperthyroidism, cancer or other conditions
Problems with the pituitary gland is also a possible cause, but is much rarer. In these cases, the pituitary gland does not release sufficient quantities of Thyroid Stimulating Hormone so the thyroid gland doesn’t increase production.
Hypothyroidism can be effectively treated with supplementary hormones. Your blood levels must be monitored and occasionally the dosage may need to be altered. There is no single dosage for hypothyroidism so regular monitoring is important to prevent relapse of this thyroid disorder.
The thyroid gland isn’t usually visible but when it enlarges, it’s known as a goitre and is seen at the front of the throat. A goitre may or may not produce symptoms, depending on the reason it has developed.
Some of the common causes of goitres are:
- Underlying condition such as Hashimoto’s or Grave’s Disease
- Inflammation of the thyroid gland can affect hormone production
- Thyroid cancer. Malignant cells can grow in nodules on the thyroid gland.
- Thyroid nodules. Not all thyroid nodules are cancerous. Clumps of thyroid tissue can overgrow and produce excessive hormones.
- Iodine deficiency in the diet. This is a rare cause in developed nations.
The underlying cause will determine the symptoms. For example, Grave’s Disease causes hyperthyroidism while Hashimoto’s Diseases causes hypothyroidism. Therefore, the symptoms of each are very different.
The underlying cause determines the goitre treatment. hypothyroidism, hyperthyroidism, nodules and cancer will all be treated but if the goitre is symptomless your doctor might adopt a “wait-and-see” approach. If the goitre is causing physical discomfort with breathing or swallowing, surgery or radioactive treatment may be necessary.
Thyroid cancer, another type of thyroid disorder, statistically affects 1.2% of people, women more often than men at the ratio of 3:1. It typically appears after the age of 30 and becomes more aggressive with older onset. Thyroid cancer is usually symptomless at first, before causing hoarseness, vocal changes and a visible lump in the throat. (10)
For some people, a lump in the throat is the only detectable sign. Pain is rarely an early feature of thyroid cancer.
Thyroid cancer presents as nodules but very few nodules are cancerous. In fact, less than 1% of thyroid nodules are cancerous, just to put it into perspective. These nodules are often an incidental finding while undergoing investigations for unrelated symptoms, such as musculoskeletal neck pain.
Types of thyroid cancer
There are four different types of thyroid cancer: anaplastic, medullary, follicular and papillary. 95% of thyroid cancers fall into the latter two categories, follicular and papillary. These two types of cancer have a cure rate of 98% with the right treatment. Medullary and anaplastic cancers are relatively rare and the prognosis isn’t quite as positive.
The treatment for thyroid cancer is unique because the thyroid cells absorb iodine, and none of the other cells in the body do. This allows doctors to use radioactive iodine to specifically target the cells of the thyroid while leaving the rest of the body relatively untouched. The benefits of this are huge: no hair loss and no nausea and vomiting.
Treatment often combines radioactive iodine therapy with either partial or full surgical removal of the thyroid gland. (11)
Not all patients require radioactive iodine therapy; surgery can offer a complete cure to this thyroid disorder in some cases.
For more aggressive cancers such as medullary, removal of the lymph glands in addition to the whole thyroid gland is also necessary.
A much simpler way to describe nodules is overgrowth of tissue. Nodules are a clump of tissue that grows together creating a lump. By the age of 60, at least half of both men and women have a thyroid nodule although they may not be aware of the fact.
Nodules can appear in many forms; some are solid while others are filled with bodily fluids or blood. The majority of nodules are benign; only a tiny percentage are cancerous. Some people develop many nodules during their lifetime but still remain completely asymptomatic.
A diagnosis of thyroid nodules can arise due to symptoms of hyperthyroidism as these clumps of tissue may produce T3 and T4. Particularly large nodules have the potential to interfere with breathing or make swallowing uncomfortable.
Other than cancer, there is often no identifiable cause of the nodules. It may be genetic; some cases tend to run in the family. Iodine deficiency is another possibility but this is rare in developed countries.
Risk factors for developing nodules include older age, being female and a past history of Hashimoto’s Disease or radiation.
Once cancer is eliminated as a possibility, watchful monitoring is the usual plan with annual scans to check size and growth. Surgery may be necessary at a later date if the nodule interferes with functioning. If the nodule is causing hyperthyroidism, the usual treatments for this condition will be given.
Hashimoto’s Thyroiditis (Hashimoto’s Disease)
This type of thyroid disorder is one of the most common types of thyroid condition and gets its name from the Japanese surgeon who first identified it in 1912. Hashimoto’s is an autoimmune condition where the immune system attacks the thyroid gland. (12)
This causes inflammation in the thyroid and makes it difficult to produce the essential T3 and T4 hormones.
If your thyroid gland cannot keep up with the body’s requirements for T3 and T4, it leads to hypothyroidism. There are many causes of hypothyroidism but Hashimoto’s is the most common.
The onset of Hashimoto’s is very insidious and it may take a long time to become hypothyroid. It’s possible for the disease to be present for many years and remain invisible. In many cases a goitre is the first sign that’s noticeable, caused by the thyroid gland working so hard for so long. If Hashimoto’s is not treated, the disease can destroy the whole thyroid gland.
Lots of autoimmune conditions have no easily identifiable underlying cause. However, if you already have an autoimmune condition, you are more likely to develop Hashimoto’s. Examples of other autoimmune conditions include Type 1 Diabetes, Rheumatoid Arthritis and Addison’s Disease. Women are seven times more likely to develop Hashimoto’s Disease than men.
In the same way that other autoimmune conditions can lead to Hashimoto’s, the thyroid disorder also increases your risk of developing other autoimmune conditions too. Your doctor may want to monitor you and carry out routine screening tests periodically. Thyroid lymphoma is a very rare complication of Hashimoto’s and is very curable when caught early.
Hashimoto’s Disease cannot be prevented but is treatable, just like hypothyroidism from any other cause. Regular monitoring of blood levels of thyroid hormones is essential to keep treatment at the right level but no other interventions are usually necessary.
Grave’s Disease is similar to Hashimoto’s Disease but causes the opposite response. Also an autoimmune condition, Grave’s Disease overstimulates the thyroid causing hyperthyroidism.
Like many autoimmune conditions, there is an element of genetic inheritance to the disease, making individuals more likely to succumb if there is a family history. Women are typically more affected than men.
In Grave’s Disease, the thyroid enlarges and produces too many hormones due to the immune system creating antibodies that mimic TSH, the trigger the pituitary normally produces. This fake TSH stimulates the thyroid gland, causing it to work harder, produce more hormones and grow due to the extra effort.
Out of all the typical hyperthyroidism symptoms (see further up), Grave’s Disease is the only condition that causes bulging eyes, plus inflammation of the eyes. The inflammation can vary from mild to severe and may be sensitive to light. (13)
In rare cases, individuals may also notice skin-thickening on their shin, together with lumps and red patches. This is pretibial myxedema, a complication of Grave’s Disease, and although it may be irritating it’s not serious.
Grave’s Disease can be treated successfully like other forms of hyperthyroidism.
The above information provides a comprehensive overview of the thyroid, its function, what can go wrong and how it’s treated. The symptoms of any kind of thyroid disorder can be very vague so it’s always essential to get checked out with a doctor rather than attempting to self-diagnose.
The good news is that the vast majority of thyroid disorders can be successfully treated with no significant, long-term complications but proper diagnosis is essential.