The thyroid gland produces hormones to control metabolism and growth. Thyroid problems occur when the gland becomes over active (hyperthyroidism) or under active (hypothyroidism) through disease. Symptoms of an overactive thyroid include weight loss/gain, fatigue, muscle weakness and breathing difficulty. Symptoms of an under active thyroid include weight gain, slow heart rate, hoarse voice, flaky skin. The thyroid can also develop nodules that may become cancerous.

Causes of thyroid problems

When the thyroid gland produces too much thyroxine and triiodothyronine hormones then it is referred to as hyperthyroidism. This is caused by a number of conditions.

Graves' disease – this is the common cause of an over-active thyroid and is a condition of the immune system. The body produces antibodies to help fight infections but with an autoimmune condition the antibodies attack healthy tissue. Graves' disease can also affect the eyes resulting in discomfort and vision problems.

Thyroid nodules – lumps, known as nodules, can develop on the thyroid which can contain abnormal tissue that affects the production of the two thyroid hormones thyroxine and triiodothyronine..

When two or more nodules are present on the thyroid gland it is called toxic multinodular goitre. If only one nodule is present the condition is called a toxic thyroid nodule.

Iodine – iodine is found in food and used by the thyroid gland to produce hormones. Too much iodine (through supplements) can trigger the production of too much thyroxine and triiodothyronine. This usually only occurs if non-toxic nodules are present in the gland.

Medications – a medication called 'amiodarone' which is used to control an irregular heartbeat can cause hyperthyroidism if non-toxic nodules are in the thyroid gland. Amiodarone contains iodine.

Thyroid cancer – hyperthyroidism can be caused by cancer in the thyroid follicles (known as follicular thyroid cancer). Cancer cells in the gland can begin to produce the thyroid hormones on its own.

When the thyroid gland doesn't produce enough thyroxine, hypothyroidism (under-active thyroid) occurs. The main causes of hypothyroidism are listed below.

Autoimmune problems – an autoimmune reaction causes antibodies to attack thyroid gland cells resulting in inflammation called 'thyroiditis'. This inflammation damages the gland preventing the production of enough throxine.

Treatment for over-active thyroid – over-treatment for hyperthyroidism using radioactive iodine or surgery can cause the thyroid to become under-active.

Iodine deficiency – although rare, a lack of iodine in the diet can cause hypothyroidism.

Viral infection – the thyroid gland can become inflamed as a result of a viral infection.

Birth defect – if the thyroid gland doesn't develop properly in the womb, a baby can be born with an under-active thyroid. The condition, known as congenital hypothyroidism, is usually identified during the neonatal screening process.

There are many symptoms to both an over-active thyroid and an under-active thyroid although it is unusual to experience them all. The main symptoms for both conditions are listed below.

Over-active thyroid symptoms

Symptoms associated with hyperthyroidism include:

• breathing difficulties
• problems sleeping
• mood swings
• fatigue
• muscle weakness
• frequent need to pass stools or urine
• diarrhoea
• streatorrhoea (fatty stools)
• increased appetite
• weight gain or loss
• infrequent menstruation or periods stopping altogether
• hyperactivity
• loss of libido (sex drive)

• swollen neck (caused by inflammation of the thyroid gland)
• heart rate increase while at rest
• difference in rhythm between the heart and pulse
• tremors
• moist skin
• red palms
• nails becoming loose
• hair loss (patches)
• itchy skin
• muscle twitches in the face and limbs

• fever
• dehydration
• jaundice
• confusion
• agitation
• hallucinations

• sensitivity to the cold
• constipation
• feeling tired
• muscle aches
• muscle weakness
• muscle cramps
• dry skin
• weight gain
• brittle hair
• brittle nails
• lack of concentration
• depression

• puffy face
• dull expression
• thinning eyebrows
• hoarse voice
• hearing problems (even deafness)
• anaemia
• slow heart rate

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