The thyroid gland is a vital hormone that plays a major role in the human body's metabolism, growth, and development. The thyroid gland regulates many body functions by constantly releasing a steady amount of thyroid hormones into the bloodstream. Whenever the body needs more energy in instances like growth or getting a cold, or while pregnant, the thyroid gland produces more hormones.

What causes thyroid disease?

Thyroid disease is a general term for a medical condition wherein the thyroid gland doesn’t make the right amount of hormones.

If the thyroid gland makes either too much or too little hormones, it leads to thyroid disease. There are different types of thyroid disease, including hyperthyroidism, hypothyroidism, thyroiditis, and Hashimoto’s thyroiditis.

Improper thyroid gland functioning can impact your entire body. Too much thyroid hormone causes hyperthyroidism and too little thyroid hormone can lead to hypothyroidism. Both these conditions are serious and need treatment.

Who can be affected by thyroid disease?

Thyroid disease can affect anyone. In some cases, its presence starts right from birth (typically hypothyroidism), and in certain other cases, it can develop as one age (often after menopause in women).

Studies show that a woman is about five to eight times more likely to be diagnosed with a thyroid condition than a man.

Factors that can trigger a thyroid condition:

• Having a family history of thyroid disease
• Having a medical condition like pernicious anaemia, Type 1 diabetes, primary adrenal insufficiency, lupus, rheumatoid arthritis, Sjögren’s syndrome, and Turner syndrome
•  Taking some medication that’s high in iodine (amiodarone)
• Age above 60, especially in women
• Past treatment for a thyroid condition or cancer (thyroidectomy or radiation)

Hypothyroidism (underactive thyroid)

This occurs when the thyroid gland doesn't make enough thyroid hormone. Hypothyroidism may not cause noticeable symptoms in its early stages. Over time, hypothyroidism that isn't treated can lead to other health problems, such as high cholesterol and heart problems.

Hypothyroidism symptoms may include:

• Tiredness
• Sensitivity to cold
• Constipation
• Dry skin
• Weight gain
• Puffy face
• Hoarse voice
• Muscle weakness
• Menstrual cycles that are heavier than usual or irregular
• Slowed heart rate, also called bradycardia
• Depression

Hyperthyroidism (overactive thyroid)    

When the thyroid gland makes too much thyroid hormone, it results in a condition called Hyperthyroidism or overactive thyroid.  With hyperthyroidism, the body's metabolism speeds up causing many symptoms, such as weight loss, hand tremors, and rapid or irregular heartbeat.

Hyperthyroidism can cause many symptoms, including:

• Losing weight
• Fast heartbeat, a condition called tachycardia
• Nervousness, anxiety, and irritability
• Tremor, usually a small trembling in the hands and fingers
• Changes in menstrual cycles
• Increased sensitivity to heat
• Changes in bowel patterns, especially more-frequent bowel movements
• An enlarged thyroid gland, sometimes called a goitre, which may appear as a swelling at the base of the neck
• Tiredness and muscle weakness
• Sleep problems.

Subclinical Hypothyroidism

Subclinical hypothyroidism (SCH), which is also referred to as mild thyroid failure, is diagnosed when peripheral thyroid hormone levels are within normal reference laboratory range but serum thyroid-stimulating hormone (TSH) levels are mildly elevated. This condition occurs in 3% to 8% of people, is more common in women than men, and its prevalence increases with age.

It usually doesn't cause symptoms. However, it can sometimes present with mild symptoms of hypothyroidism, which include:

• Fatigue
• Unexplained weight gain
• Constipation
• Depression and/or decreased attention span
• Being unable to tolerate cold temperatures
• Dry, coarse skin and hair
• Diastolic hypertension (high blood pressure)
• Frequent and heavy menstrual bleeding.

Thyroid Tests

Thyroid tests help to check how well your thyroid is working and reveals the cause of problems such as hyperthyroidism or hypothyroidism. Blood tests help to check thyroid function. 

TSH test

Checks the amount of TSH in the blood first. TSH is a hormone made in the pituitary gland that tells the thyroid how much T4 and T3 to make.

A high TSH level indicates hypothyroidism, or an underactive thyroid, meaning the thyroid isn’t making enough hormone. As a result, the pituitary keeps making and releasing TSH into the blood.

A low TSH level usually means, hyperthyroidism, or an overactive thyroid. This occurs when the thyroid is making too much hormone, so the pituitary stops making and releasing TSH into the blood.

If the TSH test results are not normal, you will need at least one other test to help find the cause of the problem.

T4 tests

A high blood level of T4 means you have hyperthyroidism. A low level of T4 may mean you have hypothyroidism.

T3 test

If your healthcare professional doubts you may have hyperthyroidism even though your T4 level is normal, you may have a T3 test to confirm the diagnosis. Sometimes T4 is normal yet T3 is high, so measuring both T4 and T3 levels can be useful in diagnosing hyperthyroidism.

Thyroid antibody tests

Measuring levels of thyroid antibodies help to diagnose an autoimmune thyroid disorder such as Graves’ disease, which is the most common cause of hyperthyroidism, and Hashimoto’s disease, the most common cause of hypothyroidism. Thyroid antibodies are released whenever your immune system attacks the thyroid gland by mistake. A thyroid antibody test might be required if the results of other blood tests suggest thyroid disease.

Radioactive iodine uptake test

Also called a thyroid uptake test, helps check thyroid function and find the cause of hyperthyroidism. The thyroid “takes up” iodine from the blood to make thyroid hormones, which is why this test is called an uptake test. The health care professional may ask to avoid foods high in iodine or medicines containing iodine for a week before the test.

For this test, the person will be asked to swallow a small amount of radioactive iodine in liquid or capsule form. A gamma probe in front of your neck measures how much radioactive iodine your thyroid takes up from your blood.

If your thyroid collects a large amount of radioactive iodine, you may have Graves’ disease. 

Imaging tests such as ultrasound and thyroid scan are also used to diagnose and find the cause of thyroid disease.

To Conclude

If you're feeling tired for no reason or if you have other symptoms of suspected thyroid disease, it is wise to diagnose and understand your thyroid health. Just because you’re not showing any signs or symptoms of a thyroid disorder, also doesn’t mean it’s not there. 

Catching a thyroid nodule early on can decrease your chances of developing an overactive thyroid. Early detection also helps to treat more serious conditions including thyroid cancer.

A regular and timely diagnosis helps with knowing and maintain your thyroid health.