Hypothyroidism

Download the hypothyroidism information sheet.

Hypothyroidism is usually a permanent condition where the thyroid gland is underactive and cannot produce enough thyroid hormone.

Hypothyroidism is the most common thyroid disorder in Australia, affecting around 1 in 33 Australians1. It is more common in women than men, and in people aged more than 60 years1.

Primary hypothyroidism is where the thyroid gland is unable to produce sufficient thyroid hormone.

Secondary hypothyroidism is rare, and caused by problems with the pituitary gland, which normally signals the thyroid to produce thyroid hormone. When the pituitary’s function is impacted (for example due to a pituitary lesion), it may not produce enough thyroid stimulating hormone (TSH), resulting in low levels of thyroid hormone being made by the thyroid gland.

Subclinical hypothyroidism is a condition in which there is an elevation of thyroid stimulating hormone levels with normal thyroid hormone levels. It may cause mild symptoms of hypothyroidism and can progress to clinically diagnosed hypothyroidism in some people.

In Australia, the most common cause of hypothyroidism is Hashimoto’s disease, also called Hashimoto’s thyroiditis. This is an autoimmune disorder that causes the immune system to attack the thyroid gland. This results in swelling and inflammation of the thyroid gland and destruction of thyroid cells.

Other causes of hypothyroidism include:

• Surgery to remove all the thyroid gland (total thyroidectomy) or part of the thyroid gland (hemi-thyroidectomy or lobectomy)
• Radioactive iodine used to treat an overactive thyroid
• Congenital hypothyroidism – thyroid gland defects which are present from birth
• Genetic disorders
• Radiation treatments to the head and neck, for example radiotherapy for cancer
• Iodine deficiency due to a lack of iodine in the diet (which is uncommon in Australia due to fortification of baked bread with iodised salt, except in pregnant women who have higher iodine requirements)
• Immunotherapy medications for cancer treatment

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The symptoms of hypothyroidism depend on its severity and the underlying cause. The symptoms can start slowly and worsen gradually over time as thyroid function deteriorates.

Many symptoms of hypothyroidism are not specific to this condition, and it therefore can be hard to identify early. These symptoms are also common in people who do not have hypothyroidism. Determining the cause of your symptoms through pathology testing is very important.

Symptoms can include:

• Increased sensitivity or intolerance of cold temperatures
• Fatigue, weariness, lethargy
• Weakness
• Dry, rough, and/or cold skin / pale skin
• Dry and brittle hair and/or hair thinning
• Constipation
• Unexplained weight gain
• Depression or low mood
• Hoarse/deep voice, slow speech
• Poor concentration / reduced attention span
• Joint and/or muscle aches and pains, cramps
• Heavy or irregular menstrual periods
• Fluid retention – swollen face, hands, ankles and/or feet
• Difficulty falling asleep or staying asleep
• Breathlessness
• Difficulty getting pregnant
• Slow heart rate

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Your doctor may ask you questions about:

Your personal health history, as well as your family’s health history. This may include questions about any thyroid disease or autoimmune disorders, any previous radiation therapy or thyroid surgery, any recent infections or illnesses, your pregnancy history and plans for conception, current and previous medications, any other medical conditions or concerns, your diet and any smoking history.

Your doctor may also ask you about any symptoms that may suggest thyroid disease (see ‘Symptoms of hypothyroidism’).

The physical examination may include feeling the front of your neck to check for thyroid swelling (goitre), checking your pulse (heart rate) and reflexes, and looking for any skin changes.

If symptoms suggest hypothyroidism, the next test your doctor will do is a blood test to measure the level of thyroid stimulating hormone (TSH). This involves taking a small amount of blood and sending it to the lab for tests.

A blood test to measure thyroid antibodies can check for thyroid autoimmune disease. This can be done on the same blood sample as the thyroid function test.

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The goal of treatment is to improve symptoms and restore normal bodily function through replacement of thyroid hormone with levothyroxine. For most people, this usually means lifelong treatment.

If you have primary hypothyroidism, you will usually need lifelong treatment with levothyroxine (often simply referred to as thyroxine) tablets. This medication is taken once per day, as soon as you wake in the morning at least 30-60 minutes before breakfast, coffee, tea and other medications. (Alternatively, it can be taken 3-4 hours after a meal.) This is because food and medications (especially calcium and iron supplements) reduce absorption of levothyroxine tablets. Always tell your doctor or pharmacist what other medications and supplements you take in case these interfere with thyroxine. It is also important to check whether the brand of thyroxine you are on needs to be refrigerated. For brands of thyroxine that do not require refrigeration, they should be stored at in its original packaging below 25 degrees Celsius away from direct sunlight.

The dose needs to be carefully monitored with blood tests to ensure the correct dose is given and avoid hormone levels getting too high or low. If thyroid hormone levels go too high, symptoms can include an increase in your heart rate, unexplained weight loss, anxiety/nervousness, sweating, diarrhoea and an intolerance to hot temperatures. If your dose is too low, symptoms such as feeling cold, constipation, tiredness/lethargy etc. may start to return (see ‘Symptoms of hypothyroidism’). It is common for doses to be frequently adjusted at the start of treatment until you reach a stable dose and to make sure you are receiving the optimum dose that brings your thyroid function into the normal range.

Normally, a doctor will adjust your thyroxine dose to your TSH and FT4 levels. In the case of secondary hypothyroidism, the TSH will always be low and therefore only the thyroid hormones themselves (FT4) should be considered when adjusting thyroxine dose, aiming for FT4 to be in the upper half of the normal reference range.

Once the dose is stabilised, your doctor will recommend at least yearly check-ups to monitor your thyroid hormone levels and adjust treatment if necessary. Furthermore, thyroid hormone requirements are closely related to weight, and so you may need to check your thyroid hormone levels and adjust treatment if you have a significant change in weight. Thyroid function blood tests should always be undertaken in the morning before you take your daily dose of thyroxine, as performing the blood test after taking your thyroxine tablets will affect your FT4 levels.

For some people who take thyroxine, symptoms persist even though medication is taken routinely and TSH levels return to normal. These symptoms may be caused by other health problems, for which your doctor can investigate. Symptoms may also persist because the dose of thyroxine may not meet the needs of every individual patient, for reasons that are not yet clear. Combined treatment of T3 with thyroxine is sometimes prescribed, although there is no evidence to show it works better than thyroxine alone.2

Treatment of hypothyroidism with desiccated thyroid extract (made from porcine [pig] thyroid) is not approved as a medication in Australia. This is because the amount of thyroxine absorbed from desiccated thyroid extract can vary from one batch to the next, and result in variable blood test results. There also remains the remote possibility of the extract containing animal transmitted viruses.

If you have subclinical hypothyroidism and few or no symptoms, and your TSH is not too high, you will not require thyroid hormone replacement. You will require follow-up blood tests to ensure that you are not developing clinical hypothyroidism. Depending on the level of TSH and if thyroid antibodies are found, these tests should initially be performed at least every 6-12 months.

If you have subclinical hypothyroidism and some symptoms, your doctor may decide on a trial of thyroxine for a few months to see if it helps. If your TSH is above a certain level, even in the absence of symptoms, your doctor may also recommend thyroxine treatment.

If you have hypothyroidism, it can help to understand the symptoms associated with too much or too little thyroid hormone. By monitoring symptoms and discussing any changes with your doctor, your medication dose can be adjusted to avoid under or over treatment.

If you are taking thyroid hormone replacement medication (thyroxine), it is important to take the medicine every day, for the rest of your life, even when you feel better. This is important to keep your thyroid hormone levels in a normal range and avoid symptoms returning. Thyroid hormone is also important for maintaining normal bodily functions.

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You should see your doctor if you have a family history of thyroid disease and/or develop symptoms or have any other concerns.

If you are taking medication for hypothyroidism, see your doctor if symptoms change or get worse. This can mean your dose needs to be changed. Your dose may be too high if you develop heart palpitations, unexplained rapid weight loss, shakiness, faintness or sweating. Your dose many be too low if you develop feeling excessively cold, constipation, tiredness/lethargy etc. (see ‘Symptoms of hypothyroidism’).

Seeing your doctor or having a medical problem can be stressful. It often takes time for information to sink in and it is very common to feel overwhelmed by what is happening. Sometimes it helps to write down questions before you go.

Some questions that might be useful for you are:

• What type of hypothyroidism do I have?
• Is my hypothyroidism permanent or temporary?
• Will I need to take thyroid hormone replacement medication?
• When should I take my medication?
• Should other members of my family get checked for hypothyroidism?
• How often will I need my thyroid hormone levels checked and monitored?
• What if I want to get pregnant?
• When do I need another appointment?

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Autoimmune disorder – A condition where the body’s immune system attacks healthy cells.

Congenital – A condition present from birth.

Hashimoto’s disease – An autoimmune disease where the immune system attacks the thyroid gland. It causes inflammation and swelling of the thyroid.

Subclinical – When a disease is not severe enough to reach the criteria for diagnosis.

References

1.So M, MacIsaac RJ, Grossmann M. Hypothyroidism. Aust Fam Physician. 2012;41(8):556-562.

2.Walsh JP. Managing thyroid disease in general practice. Med J Aust. 2016;205(4):179-184.

3. Statement on thyroxine preparations available in Australia. Endocrine Society of Australia. Accessed May 16, 2026. https://www.endocrinesociety.org.au/position-statements.asp#thyroxine

4. Patient’s medication choice of brand. Australian Thyroid Foundation. https://www.thyroidfoundation.org.au/news/13027618

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Created by Dr Joanna Gong (Endocrinologist, Royal Melbourne Hospital and Baker Heart and Diabetes Institute)

Reviewed by Professor Leon Bach (Endocrinologist, Alfred Hospital and Monash University), Dr Arunan Sriravindrarajah (Endocrinologist, Royal Prince Alfred Hospital) and Ms Beverley Garside from the Australian Thyroid Foundation (patient advocate).

Last reviewed 10 June 2026