Thyroid hormone replacement therapy

If your whole thyroid is removed, your body will no longer produce the hormones that maintain your metabolism, and you will be prescribed a hormone tablet to replace thyroxine (T4). This is known as thyroid replacement therapy.

Many people who have only part of the thyroid removed won’t need thyroid hormone replacement therapy because the remaining lobe will continue to make enough hormones.

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Taking thyroid hormone tablets

You will usually start taking hormone replacement tablets while in hospital recovering from the surgery. You will need to take a hormone tablet every day for the rest of your life.

Taking thyroid hormone tablets can have two roles:

Keeping your body’s metabolism functioning at a normal healthy rate – Without hormone replacement medicine, your metabolism will slow down and you will develop the symptoms of hypothyroidism, such as depression or weight gain.

Reducing the risk of the cancer coming back – Taking thyroid hormone tablets stops your pituitary glands from releasing too much of another hormone called thyroid-stimulating hormone (TSH). It is thought that high levels of TSH may encourage any thyroid cancer cells remaining after treatment to grow.

For this reason, if the doctor thinks the cancer has a medium to high risk of recurring, they will recommend you take a high dose of T4 to reduce the level of TSH. This is known as TSH suppression.

Finding the right dose

You’ll be carefully monitored when you start thyroid hormone replacement therapy. You’ll have blood tests every 6–8 weeks to help your doctor adjust the dosage until it is right for you. Usually, the initial dose needs only small adjustments.

A small number of people may experience hypothyroidism or hyperthyroidism during the adjustment period. However, once you are taking the right dose, you should not experience side effects.

Tips for taking T4 medicines

Take your T4 medicine at the same time every day to get into a routine. Take it on an empty stomach with a glass of water and wait 30 minutes before eating.
Store medicines in the fridge to maintain the T4 level in the tablets. If you are travelling, the medicine will last up to 30 days without refrigeration. Some T4 medicines do not need refrigeration – check with your doctor or pharmacist.
If you miss a dose, you should usually take it as soon as you remember. But if it’s almost time to take the next dose, skip the dose you missed.
Wait two hours before taking calcium or iron supplements as these affect the stomach’s ability to absorb the T4.
Check with your doctor if it’s safe to continue taking other medicines or supplements.
Tell your doctor if you are pregnant or are planning to get pregnant, as you may need to take a higher dose.
Don’t stop taking the T4 medicine without discussing it with your doctor.

This information was last reviewed in January 2020. View who reviewed this content.

A/Prof Diana Learoyd, Endocrinologist, Northern Cancer Institute, and Northern Clinical School, The University of Sydney, NSW; Dr Gabrielle Cehic, Nuclear Medicine Physician and Oncologist, South Australia Medical Imaging (SAMI), and Senior Staff Specialist, The Queen Elizabeth Hospital, SA; Dr Kiernan Hughes, Endocrinologist, Northern Endocrine and St Vincents Hospital, NSW; Yvonne King, 13 11 20 Consultant, Cancer Council NSW; Dr Christine Lai, Senior Consultant Surgeon, Breast and Endocrine Surgical Unit, The Queen Elizabeth Hospital, and Senior Lecturer, Discipline of Surgery, University of Adelaide, SA; A/Prof Nat Lenzo, Nuclear Physician and Specialist in Internal Medicine, Group Clinical Director, GenesisCare Theranostics, and The University of Western Australia, WA; Ilona Lillington, Clinical Nurse Consultant (Thyroid and Brachytherapy), Cancer Care Services, Royal Brisbane Women’s Hospital, QLD; Jonathan Park, Consumer.

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