Index to this Health
Guide
Hashimoto's
Thyroiditis
Subacute Thyroiditis
Silent Thyroiditis
Post Partum Thyroiditis
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Health
Guides on Thyroid Disease
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Hashimoto's
Thyroiditis
Thyroiditis, or
inflammation of the thyroid gland, has many causes. The most common
cause is Hashimoto's thyroiditis. This is a chronic inflammatory
disorder of the thyroid gland caused by abnormal blood antibodies
and white blood cells attacking and damaging thyroid cells. The
end result of this so-called "autoimmune" destruction is hypothyroidism
caused by the complete absence of thyroid cells. However, in many
patients, sufficient thyroid reserve remains to prevent hypothyroidism.
Clinical Features
Patients with Hashimoto's thyroiditis
are usually, young, middle-aged or older women. They often have no
symptoms apart from mild pressure in the thyroid gland and tiredness.
In the early stages there is a goitre which is firm, slightly irregular,
and sometimes slightly tender. Pain occurs in about 10% of cases.
Laboratory
Tests
The diagnosis of Hashimoto's thyroiditis
is confirmed by finding high levels of antibodies in the blood. These
work against the patient's own thyroid proteins. The diagnosis can
be firmly established by doing a thyroid biopsy. A needle is inserted
into the thyroid gland and some cells removed and smeared onto a glass
slide. The pathologist will see many blood lymphocytes in the smear
which indicate the nature of the inflammatory reaction in the thyroid
gland. All women over 50 years of age should be screened by a TSH
test; a high TSH will be found in 10-15% and will almost invariably
be due to Hashimoto's thyroiditis. Treatment
Treatment of Hashimoto's thyroiditis
is to take thyroid hormone replacement (thyroxine) as soon as the
diagnosis is made, even if thyroid function is, at that time, normal.
Thyroid hormone is given for three reasons:
- it shrinks the goitre by suppressing
production of thyroid stimulating hormone (TSH) by the pituitary
gland;
- it anticipates the development
of thyroid failure and the resulting low levels of thyroid hormone
since the disease may progress with time;
- it seems to have an effect on
blood lymphocytes which cause the damage and destruction in the
thyroid gland.
The dose of thyroxine is the same as
for hypothyroidism although slightly larger doses may be needed initially
to shrink the goitre. Many patients, particularly younger people,
are concerned about the goitre itself which may remain for several
years before disappearing. The goitre will shrink over a period of
6 to 18 months in most patients. When the gland has shrunk, it is
not functioning and the patient would be hypothyroid if treatment
were not given. Therefore, thyroxine treatment for Hashimoto's thyroiditis
must be taken for life. Patients with Hashimoto's thyroiditis should
be seen by their family doctors at least once a year to check that
the dose of thyroxine is correct and that the goitre has decreased
in size. Top
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Subacute
Thyroiditis
Subacute Thyroiditis is about ten times
less common than Hashimoto's Thyroiditis. It is a transient form of
thyroiditis causing hyperthyroidism but not requiring treatment with
radioactive iodine or by thyroidectomy. There
is evidence that subacute thyroiditis is caused by a viral infection
since most patients have had a throat infection a few weeks before
the thyroiditis. The condition occurs in small epidemics, usually
in association with known viral infections.
Clinical Features
The main symptoms are a painful swelling
of the thyroid gland and symptoms of hyperthyroidism. These symptoms
include heat intolerance, nervousness, palpitations and weakness.
The hyperthyroidism is due to the leaking of thyroid hormones from
the damaged thyroid cells as a result of the viral infection. This
is a temporary situation since once the virus infection has run its
course, the thyroid cells recover their normal state. On examination,
the patient has a very tender, swollen thyroid gland and mild signs
of hyperthyroidism. Laboratory
Tests
About half of the patients with subacute
thyroiditis develop hyperthyroidism. In those who do, the diagnosis
can be confirmed by showing high levels of blood thyroid hormones.
The blood erythrocyte sedimentation rate (ESR), a very useful test
for this condition, is very high (over 80). The radioactive iodine
uptake test gives very low results. The normal range for this test
is from 15-20%. In subacute thyroiditis the uptake is usually less
than 1%. This is because the virus infected cells are "sick" and unable
to take up iodine. Treatment
The treatment for milder forms of this
condition is aspirin, given for the inflammation, swelling and pain.
Patients with severe symptoms may be given steroids (cortisone). In
most cases, the patient recovers within a few days. In a few people,
the illness lasts longer and in some it recurs. In almost one-quarter
of patients, a temporary phase of hypothyroidism, which may require
treatment with thyroxine, occurs as a result of the severe damage
to the thyroid cells. Eventually, the cells recover and the thyroxine
treatment can cease.
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Silent
Thyroiditis
Another cause of thyroiditis, which
occurs about as frequently as subacute thyroiditis, is "silent" thyroiditis.
This is so named because there are no symptoms or signs of thyroid
inflammation. The patient is hyperthyroid at first and may have the
same symptoms as patients with Graves' hyperthyroidism, but then goes
through a hypothyroid phase before full recovery. |
Postpartum
Thyroiditis
Postpartum thyroiditis occurs frequently
in women with a past history of thyroid disease who have recently
delivered a baby. In most respects, silent and post partum thyroiditis
resemble Hashimoto's thyroiditis except that the gland tends to
recover and thyroid hormone treatment need be given for only a few
weeks. However, it does differ from subacute thyroiditis in that
recurrences are common.
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printed version of this Health Guide is available to health care
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Production of
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the official policy of Health Canada. |
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