Hashimoto's thyroiditis

International Classification (ICD)	E06.-
Symptoms	Tiredness (Fatigue), Listlessness, Reduced performance/strength, depressive moods, Weight gain, Sensitivity to cold, Cycle irregularities, Constipation, cool/dry/doughy skin, Nail growth disorders, Hair loss
Possible causes	Autoimmune disease
Possible risk factors	genetic predisposition, exogenous factors (e.g. excess iodine due to dietary supplements), female sex, hormonal changes/transitions (puberty, pregnancy and childbirth, menopause) and/or emotional stress as trigger factor in case of existing genetic predisposition

Basics

Hashimoto's thyroiditis - also called chronic immune thyroiditis, chronic lymphocytic immune thyroiditis, Hashimoto's disease, or Hashimoto's for short - refers to a chronic, inflammatory disease of the thyroid gland. It is a common autoimmune disease in which the body's immune system mistakenly perceives the thyroid gland as foreign and ultimately fights or destroys it. Specifically, the immune system produces antibodies that target structures in the thyroid tissue and cause a painless inflammation in the thyroid gland. The result: a restriction of thyroid function and, in the long term, a deficiency of the free thyroid hormones thyroxine (fT4) and triiodothyronine (fT3), which are relevant for metabolism (metabolism) - in other words, hypothyroidism.

General and incidence

Hashimoto's thyroiditis is named after the Japanese pathologist and surgeon Hakaru Hashimoto (1881 to 1934), who first described inflammation of the thyroid gland in 1912. In the course of further research into the disease, largely by the British-Swiss physician and immunologist Deborah Doniach (1912 to 2004) and the British immunologist Ivan Maurice Roitt (1927 to the present), an autoimmune genesis was discovered.

Today, chronic immune thyroiditis, which requires treatment, is one of the most common thyroid dysfunctions. Five to ten percent of the worldwide population is affected.

Hashimoto's thyroiditis is found in all age groups of the population. In terms of gender distribution, the number of affected women predominates in a ratio of 9:1. It is suspected that the sex hormones estrogen, progesterone and testosterone have an influence on the development of the disease.

Differentiation

Chronic Hashimoto's thyroiditis is an autoimmune disease that leads to loss of function of the thyroid tissue and must be distinguished from other causes of hypothyroidism, such as those caused by thyroid surgery or radio-iodine treatment.

Causes

The cause of Hashimoto's thyroiditis is an autoimmune reaction in which the immune system mistakenly perceives the thyroid gland as foreign and begins to form antibodies against it. This leads to a painless chronic inflammation of the thyroid gland, as a result of which it can no longer produce sufficient thyroid hormones (fT4 and fT3) in the long term, despite increased stimulation by the controlling hormone, thyroid-stimulating hormone (TSH). The long-term result is hypothyroidism.

The exact underlying causes of the autoimmune disease are not known to date. It is assumed to be a multifactorial process due to endogenous influences, such as genetic predisposition (keyword familial accumulation), on the one hand, and exogenous influences, such as a continuously high iodine intake, for example in the form of food supplements, on the other. Emotional stress, caused by drastic life events and/or strokes of fate (loss, separation, etc.), can also promote the onset of Hashimoto's thyroiditis - as is the case with many autoimmune diseases - if a genetic predisposition is already present. Hormonal changes and changes caused by puberty, pregnancy and childbirth or menopause are further triggers that can ultimately trigger chronic immune thyroiditis in the case of an existing predisposition.

Gender also plays a role in the development of the disease. Women are far more likely to develop chronic immune thyroiditis than men.

Symptoms

Although Hashimoto's thyroiditis is painless, it is not always symptom-free. Although the short phase of passive hyperthyroidism at the beginning of the disease usually does not cause any symptoms and the disease can run for many years without any symptoms at all, noticeable symptoms that may require treatment eventually occur, mainly due to the deficiency of thyroid hormone. However, these do not necessarily occur and generally vary in severity depending on the individual patient. Affected persons with symptoms therefore primarily perceive the hypothyroidism - and do so in a wide variety of individual ways. Symptoms that may indicate Hashimoto's thyroiditis include:

Tiredness (fatigue) and weakness.
Listlessness
Fatigue
Decreased physical and cognitive performance
Depressive moods, sadness
Weight gain (sometimes despite changes in dietary habits)
Excessive sensitivity to cold
Irregular menstrual cycles and, as a consequence, possibly reduced fertility
Constipation (constipation)
Cool, dry and/or doughy skin
Disturbances in nail growth
Hair loss (effluvium)

Since the symptoms of Hashimoto's thyroiditis are very unspecific, can also occur in the course of other diseases and are perceived very individually by those affected, a differential diagnostic clarification and differentiation from other diseases is very important - especially with regard to the choice of further procedure and therapy.

Course of the disease

There are two forms of chronic immune thyroiditis: the hypertrophic form (the "classic Hashimoto's thyroiditis" first described by Hakaru Hashimoto), in which the thyroid gland enlarges over time, is riddled with inflammatory cells, and loses function, and the atrophic form, in which the thyroid gland becomes smaller and smaller over time and atrophies. Both cases usually lead to a deficiency of thyroid hormone, hypothyroidism, in the longer term.

In the initial phase of Hashimoto's thyroiditis, the patient initially experiences a passive, i.e. temporary, hyperthyroidism, which is known as "hashitoxicosis": The inflammation destroys thyroid cells, causing a greater amount of thyroid hormone to be washed into the blood.

Passive and usually asymptomatic hyperthyroidism is in many cases not recognized at all, or often only detected by chance during routine blood tests, since it usually lasts only a few weeks, sometimes one to two months. After that, thyroid function returns to normal and eventually changes to hypothyroidism, often only after years or decades. The time course is very individual.

Diagnosis

In order to diagnose a thyroid disease or dysfunction, the thyroid function (over-, under- or normal function) is determined by blood test and the thyroid structure (morphology) is examined by ultrasound after a detailed interview including a medical history. These two parameters do not necessarily correlate and must always be considered in combination in order to finally arrive at a diagnosis and subsequently adequate therapy.

Examination of thyroid function

The healthy function of the thyroid gland is based on the following mechanism: The thyroid gland secretes the free thyroid hormones thyroxine (fT4) and a small amount of triiodothyronine (fT3), which are essential for metabolism. fT3 is also converted from fT4 outside the thyroid gland in various organs and made available to the body.

Diagram of the thyroid gland and the hormones T3 and T4

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The level of fT4 and fT3 in the blood is in turn regulated by the pituitary gland in the brain, which produces TSH. TSH is considered the most sensitive parameter with regard to a possible thyroid dysfunction: a rising TSH level is the first sign of hypothyroidism; a falling TSH level, on the other hand, is the first sign of hyperthyroidism. The pituitary gland performs a function similar to that of a thermostat in a heating system: it detects even the slightest deviations in the thyroid hormones fT4 and fT3 and adjusts the release of TSH accordingly. If the thyroid hormone level in the blood is too low, the pituitary gland secretes larger amounts of TSH; if the thyroid hormone level in the blood is too high, the pituitary gland causes TSH to drop. Continuously high TSH levels therefore provide the physician with indications of hypothyroidism, as is the case with Hashimoto's thyroiditis.

The thyroid function is examined by taking a blood sample. Antibodies directed against the thyroid gland can also be examined. In many patients with Hashimoto's thyroiditis, antibody levels against thyroperoxidase (TPO-Ak) and thyroglobulin (Tg-Ak) in particular are elevated. Even if these are already detectable in the blood, it can take years to decades before hypothyroidism finally develops that requires treatment.

Examination of the thyroid structure (morphology).

The structure of the thyroid tissue also provides information about the function or condition of the thyroid gland. By means of an ultrasound examination, the size, condition and presence or degree of inflammatory infiltration of the thyroid tissue can be determined. The typical patterns of inflammation can usually be seen on ultrasound long before other changes, such as antibodies in the blood and/or symptoms, become apparent.

Thyroid scintigraphy

Another examination and diagnostic method is thyroid scintigraphy. In this nuclear medicine examination, a mildly radioactive drug is administered to the patient either intravenously or orally. The patient must then wait about 20 minutes so that the drug - just like naturally occurring iodine - can accumulate in the thyroid gland. This allows the regional metabolism of the thyroid gland to be recorded using a gamma camera. The slightly radioactive drug is harmless; the patient excretes it in the urine within a day.

Thyroid scintigraphy is used in chronic immune thyroiditis in the initial phase to determine the cause of the passive hyperthyroidism and to delineate possible other causes of disease. Is the hyperthyroidism caused by Hashimoto's thyroiditis? Or is Graves' disease responsible for the initial hyperthyroidism? This is because different causes of thyroid disease are also treated differently. Apart from this, the non-specific symptoms that occur in Hashimoto's thyroiditis, for example, can also be signs of a variety of other diseases that must always be differentiated or ruled out before treatment begins.

Therapy

Treatment of Hashimoto's thyroiditis is based on the stage of the disease. Passive hyperthyroidism in the initial phase usually does not require treatment. Since the thyroiditis in the course of Hashimoto's disease often remains symptom-free for decades, regular specialist check-ups may continue to be sufficient. The inflammation of the thyroid gland, which usually remains lifelong and only in the rarest cases regresses spontaneously, does not normally need to be treated - in contrast to hypothyroidism, which is ultimately also the reason for possible complaints.

The aim of treatment is to compensate for the hypothyroidism by means of thyroid hormone in the form of tablets, so that the symptoms caused by it disappear. The thyroid hormone that the thyroid gland can no longer produce on its own is therefore permanently replaced by a hormone tablet (hormone replacement). The daily intake of thyroid hormone tablets is usually necessary for patients with chronic immune thyroiditis and hypothyroidism for the rest of their lives. Regular checks and, if necessary, adjustments of the medication dose - especially in special phases of life, such as during childbearing, pregnancy and breastfeeding - are extremely important.

In addition, taking the trace element selenium for several months can help to slow down those antibodies that are directed against the thyroid gland. Thus, selenium can help to slow down the course of the disease.

Forecast

The inflammation of the thyroid gland in the context of autoimmune thyroiditis is not curable, does not usually disappear by itself, and therefore remains lifelong. If the thyroid function is still largely normal despite the diagnosis, which is often the case for decades, or if the drug therapy is adequately adjusted, most patients lead a symptom-free life. Since hormone requirements may fluctuate, the dosage of hormone replacement therapy must be adjusted regularly. For this reason, regular check-ups with a specialist are important.

Living with Hashimoto's thyroiditis

The psyche often plays an important role in Hashimoto's patients. In general, the disease has a strong emotional impact. For many sufferers, the idea of having to take a tablet for the rest of their lives is initially difficult to cope with. Compared to many other autoimmune diseases, the effects of Hashimoto's thyroiditis are manageable. With normal thyroid function, the disease does not require treatment in many cases, and there is often freedom from symptoms for many years. Even if treatment is necessary, the disease is usually very treatable, provided regular check-ups with a specialist are carried out.

Prevent

Iodine is considered an essential trace element and is needed in the thyroid gland for the production of the thyroid hormones fT4 and fT3. Iodine is also essential if you wish to have children or during pregnancy - for example, for the healthy development of a baby, especially in the early stages of pregnancy.

piotr_malczyk / iStock

Accordingly, a sufficient iodine supply (keyword table salt iodization) is important - provided that the thyroid gland is healthy and fully functional. If, on the other hand, an autoimmune disease of the thyroid gland is present, continuous excessive iodine intake - such as is achieved by taking certain dietary supplements - is counterproductive, especially in the early phase of the disease, and should therefore be avoided. This is because the autoimmune disease can be further fanned by a continuously high iodine intake.

In general, an active, sporty lifestyle and a varied and healthy diet ensure that the entire organism and thus also the thyroid gland remain healthy, vital and functional.