Chronic autoimmune thyroiditis is one of the most frequent thyroid disorders.
It's an autoimmune disease. Affected immune system makes autoantibodies against the structures of thyroid gland.
Antibodies are normally made by immune system to fight foreign substances such as virus, bacteria, toxins, etc.
The result of thyroid autoantibodies attack is destruction of thyroid cells, thyroid hormones deficiency and concomitant state of hypothyroidism.
Chronic autoimmune thyroiditis has its synonyms such as Hashimoto's thyroiditis (in honour of Japanese doctor who described this disease first) or chronic lymphocytic thyroiditis.
PREVALENCE
According to statistics, this disease is more frequent in woman.
Every 0,8 person from 1000 are affected yearly.
And this statistic for woman is 3,5 from 1000 yearly.
The frequency of disease is increasing with age.
CAUSES
The exact causes of autoimmunity is not fully clear.
If summarise the statements, the role of genetic in disease development is approximately 79%, and the remnant 21% can be the influence of gonadal hormones and provocative environmental factors such can be viral infections, stress, radiation an so on.
Autoantibodies are made against different structural components of the thyroid gland.
Thyroid peroxidase autoantibodies and/or thyroglobulin autoantibodies are elevated most often.
In more rare cases there is clinical features of autoimmunity but non of the autoantibodies are detected by laboratory. In these cases other unknown autoantibodies may be presented.
It's curious that the level of thyroid autoantibodies are in positive relationship with the severity of disease.
MANIFESTATION
Clinical manifestation of Hashimoto's thyroiditis can be different.
Case 1:
Very often we meet the situation when laboratory tests for thyroid autoantibodies are positive, but the thyroid gland functions properly and its hormones are in a normal range.
When the thyroid function is normal, it's called as euthyroid state.
We can never tell how long can euthyroid state last when autoantibodies levels are high.
We just can tell that in a such situations the risks of hypothyroidism is increased.
On the thyroid ultrasound we already see the parenchymal heterogeneity.
Case 2:
If the action of thyroid autoantibodies is more aggressive and the damage of thyroid cells is severe, at the presence stage of disease the hyperthyroid state can be detected. It accounts 5% of all cases of Hashimoto's thyroiditis.
This happens due to destroyed thyroid hormone storages and releasing them to blood circulation.
This stage of disease is called hashitoxicosis and it can last for 1-2 months.
There is an active inflammation processes in thyroid gland at this time and this can cause the enlargement of the gland.
When the thyroid cells are damaged enough to cause hormones deficiency, the hypothyroid state occurs which can be in a subclinical or clinical form.
Subclinical hypothyroidism is characterised by laboratory results of high TSH and normal FT4 levels.
Clinical hypothyroidism means high TSH and low FT4 levels.
Most often the manifestation of autoimmune thyroiditis coincides to hypothyroid phase.
ULTRASOUND IMAGE
The ultrasound image of Hashimoto's thyroiditis can be different as well and it depends on the stage and severity of disease.
The thyroid ultrasound image under this diagnose can be as follow: the structure of the organ is heterogeneous, a cloud-like structure may be observed, as well as nodular formations, which are rarely cystic and can be small or large in size. Vascularisation of the gland is increased.
The gland size itself is variable. At first it can be enlarged but then the size may decrease and become atrophic.
Reactive visible lymph nodes with normal structure may be detected in the neck area. It's thought to be an answer on autoimmune inflammation processes in the thyroid gland.
SYMPTOMS
The progress of the disease is very slow, it can last for years. The symptoms occur only when thyroid hormones become deficient.
Symptoms for subclinical and clinical hypothyroidism can be the same as follows:
- skin: dry, pale, exfoliated, signs of mucosal oedema.
- hair: lower growth rate, increased loss, damaged hair ends. diffuse or local alopecia can be presented.
- heart rate: decreased - bradycardia with general weakness and decrease muscle strength.
- constipation and weight gain or unable to loose extra kilograms.
- cold intolerance.
- decreased energy and daytime sleepiness.
- depression.
- joint and muscle pain.
- hearing problems.
- memory loss
- increased menstrual bleeding.
Conditions that can be result of Hashimoto's thyroiditis or hypothyroidism are:
- high prolactin levels
- increase of cholesterol level
- anemia.
WORK OUT
To diagnose the Hashimoto's thyroiditis, these laboratory or instrumental tests are done:
Immunological tests – to detect specific thyroid autoantibodies: Anti-TPO, Anti-TG.
Hormonal tests - to check the function of thyroid gland: TSH, FT4.
Instrumental tests to see the thyroid gland structure, size, local damages: thyroid ultrasound.
All these results are summarised with the anamnesis, so the diagnosis and proper treatment / follow up plan is done.
TREATMENT
Treatment decision depends on various factors.
If the hypothyroid state is presented, the hormone replacement therapy with levothyroxine medications is started to restore euthyroid state and it must continue lifelong as the condition is chronic.
At this moment we don't have any treatment for lowering autoantibodies levels or to protect the gland from their damaging action.
Because of this if the autoantibodies exist, but thyroid functions properly, patient doesn't need any treatment, just frequent monitoring is planned.
If there is nodules in the thyroid, they must be monitored carefully and thy biopsy must be done if it's needed.
OTHER COEXISTED AUTOIMMUNE DISEASES
The autoimmune damage of different organ often coexists.
Hashimoto's thyroiditis can develop in parallel with:
- autoimmune gastritis
- alopecia
- vitiligo
- reumatoid arthritis
- also: celiac, type 1 diabetes, Addison's disease and so on.
HASHIMOTO'S THYROIDITIS AND PREGNANCY
The coexisting autoimmunity can be the reason that the chronic autoimmune thyroiditis is often associated with increased risk of early weeks miscarriages. But the next pregnancies are usually normal.
The Hashimoto's diseases itself can become a reason of difficulties getting pregnant only if the hypothyroidism is presented. So all woman with this diagnose who plan to become pregnant should be monitored carefully by the endocrinologist before conception and also during the pregnancy.
Author: Elga Giorgadze (MD of Endocrinology)
