Where is the thyroid gland and what does it do?

The thyroid gland is located in the lower part of the neck. There is one lobe on either side of the neck connected by a tissue called isthmus. Thyroid gland secretes certain hormones into the bloodstream which controls several important functions of the body.

What is an underactive thyroid gland?

When the thyroid gland fails to produce and secrete adequate thyroid hormone, it is referred to as under active thyroid or hypothyroidism.

What causes an underactive thyroid gland?

Under active thyroid or Hypothyroidism can be caused by a number of conditions which are listed below:

• Autoimmune thyroid disease: This is the most common cause for hypothyroidism. In auto immune conditions, the body’s immune system attacks the thyroid cells, erroneously thinking that the thyroid cells do not belong to this body and are not wanted.  The most common form is known as ‘Hashimoto’s thyroiditis’
• Radioactive iodine treatment (RAI): this form of treatment is given for Graves’ disease or thyrotoxicosis. There is a high chance that people who have had radioactive iodine will become hypothyroid and may need thyroxine life long.
• Surgery to correct hyperthyroidism, large goitre or to treat thyroid cancer can result in under active thyroid.
• Antithyroid drugs: Carbimazole and Propylthiouracil are antithyroid drugs, when given for an overactive thyroid can lead to under active thyroid. This is why you need to have regular monitoring by an endocrinologist.
• Medications: Lithium, which is used for certain mental disorders and amiodarone, used to control heart rhythm is known to cause hypothyroidism.
• Over the counter medicines: Some cough medicines containing large amounts of iodine can also interfere with the way the thyroid functions and cause hypothyroidism.
• Food supplements & Health foods: Foods taken in excess like kelp (seaweed) is known to cause hypothyroidism.
• Pituitary gland: Pituitary gland controls the way thyroid functions. Any abnormality of pituitary gland, which is located in the brain and regulates the thyroid hormones, is known to cause secondary hypothyroidism.
• Radiation for head and neck: Radiation involving head and neck for cancers may lead to an underactive thyroid.
• Thyroid hormone resistance: This is a rare condition, when despite taking the correct dose of thyroxine, blood test shows that you are underactive. One of the reasons may be due to thyroid hormone resistance. Your endocrinologist will investigate further to find out the type of thyroid hormone resistance and manage it accordingly.

What are the symptoms of hypothyroidism?

The symptoms of hypothyroidism develop gradually and hence may take several months years to diagnose. Sometimes hypothyroidism is diagnosed whilst having routine blood test for other conditions. Hypothyroidism can present in number of ways and the symptoms greatly vary from person to person.

Some of the most common symptoms are listed below:

• Tiredness
• Difficulty in concentration
• Intolerance to cold
• Dry skin
• Thinning of hair
• Hoarse voice
• Constipation
• Muscle weakness & cramps
• Body ache
• Carpal tunnel syndrome
• Abnormal menstrual periods
• Infertility
• Low libido
• Weight gain
• Puffy face
• Slow speech
• Low mood
• Depression
• Memory problems
• Slow heartbeat (bradycardia)

How is hypothyroidism or underactive thyroid diagnosed?

Your endocrinologist will undertake a detailed clinical history during the first consultation followed by examination and blood test/scans. A high Thyroid Stimulating Hormone (TSH) level and a low thyroid hormone levels (FT4 & FT3) usually indicates underactive thyroid. Tests are also done to find out the underlying cause for hypothyroidism and this involves testing for antibodies. Hashimoto’s, an autoimmune condition is the commonest cause for hypothyroidism. Endocrinologist will also try and find out if there are other conditions contributing to underactive thyroid.

What are the treatment options for hypothyroidism?

Your endocrinologist will prescribe thyroxine, which is a synthetic version of the thyroxine produced naturally by the thyroid gland. Levothyroxine has negligible side effects when taken in the correct dose. However rarely some people cannot tolerate and may need an alternate preparation.

Levothyroxine doses are dependant upon the person’s body weight. The dose of thyroxine is gradually increased. It may take several months before you start to feel better and the thyroid function tests to return to normal. You need to have regular monitoring by your endocrinologist.

Please ensure you get into a habit of taking thyroxine regularly at the same time of the day.

Thyroxine is best taken in the morning, with water, on an empty stomach, at least an hour before eating and drinking.  Please also ensure you do not take any calcium, iron, cholesterol lowering drugs (cholestyramine, colestipol), proton pump inhibitors like Omeprazole etc) and multivitamin tablets at least four hours after taking thyroxine as these medicines can reduce absorption of thyroxine. Grapefruit  is known to increase the absorption of thyroxine due to increased acid in the stomach. If you are taking warfarin inform your GP, so that more frequent monitoring can take place until your thyroid hormone levels are stabilised.

Let your endocrinologist know of all the medications you are taking including over the counter medications and food supplements.

As mentioned above increased dose of thyroxine may cause symptoms of an overactive thyroid and inadequate thyroxine may not relieve symptoms of an underactive thyroid.

If you are planning a pregnancy, you should let your endocrinologist know and have a thyroid function test done before you conceive. As soon as you know you are pregnant and if you are already taking thyroxine, it is recommended that the dosage is increased immediately after consulting with your endocrinologist. You should be monitored frequently by an endocrinologist during pregnancy and immediately afterwards.

To learn about hyperthyroidism or overactive thyroid, click here

Dr Chinnadorai Rajeswaran is a consultant Physician specialising in Endocrinology, Diabetes and Obesity. As a private endocrinologist he  has private endocrine, diabetes and weight loss clinics in Harley Street, London, Chennai (India), Claremont Hospital, Sheffield, Nuffield Hospital, Leeds and Simplyweight, Bradford.

He has face to face consultations with people from Barnsley, Rotherham, Chesterfield, Doncaster, Wakefield, Huddersfield, Bradford, Harrogate, Leeds, Sheffield, London and Chennai (India). He also offers video consultations.