What is thyroid hormone replacement therapy?

Thyroid hormone therapy is the use of manmade thyroid hormones to raise abnormally low levels of natural thyroid hormones in the body. Thyroid hormone is usually given in pill form and is often used to treat an underactive thyroid that is secreting little or no thyroid hormones. The most commonly prescribed thyroid hormone replacement is pure synthetic thyroxine (T4).

Who needs thyroid hormone replacement therapy?

Thyroid hormone therapy is generally prescribed when your thyroid is not making enough thyroid hormone naturally. This is a condition referred to as hypothyroidism. Other reasons for using thyroid hormone therapy may rarely include:

• To control the growth of the enlarged thyroid gland (also called goiter)

• To control the growth of nodules on the thyroid gland

• Treatment after the removal of the thyroid for benign or malignant disease

• After treatment of hyperthyroidism by radioactive iodine ablation

How is thyroid hormone replacement therapy dosage determined?

Healthcare providers do careful blood testing to find the proper dose of hormone replacement therapy for each person. The blood tests reveal levels of thyroid hormones in the blood, as well as thyroid-stimulating hormone (TSH) released by the pituitary gland. The pituitary gland plays an integral role in the functioning of the thyroid gland. It controls how much thyroid hormone is released by making TSH that "stimulates" the thyroid. Increased levels of TSH may indicate that you have an underactive thyroid or that thyroid hormone replacement needs to be increased. 

You will have lab tests to measure levels of thyroid hormones and TSH. Hypothyroidism can be a progressive disease. This needs dosage increases over time.

To make sure that your thyroid hormone replacement works properly, consider the following recommendations:

• Maintain regular visits to your healthcare provider.

• Take your thyroid medicine at least 1 hour before breakfast and any calcium or iron medicines you may take. Or take at bedtime, or at least 3 hours after eating or taking any calcium or iron medicines.

• Tell your healthcare provider of your thyroid hormone treatment before beginning treatment for any other disease. Some treatments for other conditions or diseases can affect the dosage of thyroid hormone therapy.

• Let your healthcare provider know if you become pregnant.

• Tell your healthcare provider of any new symptoms that may arise.

• Tell all healthcare providers of your thyroid condition and medicine dosage.