Thyroiditis

Thyroiditis is an inflammation not an infection of the thyroid gland

Hashimoto’s thyroiditis is a very common cause of an underactive thyroid (called hypothyroid). It usually presents in women aged between 30 and 60 years. The thyroid gland is always enlarged to some degree presenting as a small or moderate size goitre. Often the goitre has been present for 2 to 4 years and the patient has had thyroid tests which have been normal or borderline hypothyroid. If a biopsy is carried out (and often this is not required) then the thyroid will be found to be inflamed. The thyroid takes up iodine if scanned but fails to produce adequate output of thyroid hormones. As the inflammation worsens the thyroid continues to fail producing less and less thyroid hormone.This feedbacks to the pituitary head gland which increases it’s production of a hormone TSH which goes via the blood stream to the thyroid and tries to switch on thyroid production increasing the size of the gland. High levels of thyroid antibodies (microsomal) can be detected in the patient’s blood, a sign of the inflammation. There is usually no pain associated with this inflammation. This sequence of events can take months to years to develop and is the reason why some patient’s go hypothyroid sooner than others.

The treatment is to top up the thyroid hormone by giving thyroxine replacement. This often causes the thyroid goitre to shrink. However the raised thyroid antibodies can remain elevated for may years after thyroxine replacement for thyroxine does not stop the inflammation but justs tops up the thyroid hormone levels relieving the thyroid of the necessity to produce hormones.

This type of thyroiditis can be associated with other auto-immune diseases such as adrenal failure, diabetes mellitus and pernicious anaemia, so your specialist will check for these.

This is less common than Hashimoto’s thyroiditis. In this the thyroid enlarges fairly rapidly and can be very painful and tender to feel. The patient can develop a fever, feel ill, lose appetite and may have difficulty swallowing. In about half the patients there is an initial thyroid overactivity due to discharge of stored thyroid hormone from the thyroid gland caused by the inflammation. However unlike classical thyrotoxicosis (called Graves disease) the uptake of iodine on scanning is very low or non existant. Thyroid antibodies are not present to any significant degree.This early thyrotoxic state soon ends after several weeks and the patient’s thyroid hormones in the blood return to normal. Some patient’s however can become transiently hypothyroid but a full recovery is usual over a period of weeks or months. Regrettably there are some patients who require long term thyroid hormone replacement for the thyroid does not recover sufficiently. Recurrences are uncommon.

As this is a short term disease the initial thyrotoxicosis is treated differently from Graves disease usually with b blockers such as propanolol or nadolol. Pain treatment may be required, some find help with aspirin and in severe cases pain relief is achieved with steroids (prednisolone).

A silent form of subacute thyroiditis can occur. Some describe this as part Hashimoto and part De Quervain. The majority of patients are young women and this mainly occurs in the first year after pregnancy which is the reason why some call this post pregnancy thyroiditis. The patient develops an overactive thyroid without any major enlargement of the thyroid and no pain or fever. Iodine uptake is very low and distinguishes this from Graves disease where the uptake is raised. Thyroid antibodies can increase also transiently. This is a transient condition lasting weeks and usually stops spontaneously without any treatment. Therefore the treatment is often just b-blockers such as propanol or nadolol. Thyroidectomy, radioiodine or antithyoid medication is never needed. Most return to normal thyroid function but a few can become hypothyroid. In some hypothyroidism resolves whereas others require thyroid replacement therapy long term.

There is a patient organisation called the British Thyroid Foundation: if you are interested, please ask for a leaflet at your next hospital visit or contact British Thyroid Foundation, PO Box 97, Clifford, Wetherby, West Yorkshire  LS23 6XD. http://www.btf-thyroid.org

The British Thyroid Foundation has recently joined Thyroid Federation International, 96 Mack Street, Kingston, Ontario, Canada K7L 1N9.  The website can be found at   http://www.thyroid-fed.org

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Ó NHS Tayside; 2006; version 1.0

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