Definitions of NTIS


NTIS stands for Non-Thyroidal Illness Syndrome. Non-thyroidal illness syndrome is not a disease in its own right, but occurs as part of serious illness or starvation. It indicates a change in the metabolism of thyroid hormones in normal thyroid function. The importance of non-thyroidal illness syndrome is not yet fully understood.

What is Non Thyroidal Illness Syndrome?

Non-Thyroidal Illness Syndrome (NTIS) or TACITUS Syndrome is characterized by an altered metabolism of thyroid hormones with normal thyroid function. That is why it is also known as euthyroid sick syndrome. It never occurs in isolation, but only in connection with severe disease progression and starvation. See AbbreviationFinder for abbreviations related to NTIS.

There is still no clarity about the significance of this syndrome for the organism. The altered metabolism could develop to protect the organism against the extremely severe course of the disease. However, it could also be a consequential disorder. In any case, this syndrome is generally associated with a poorer prognosis in critically ill individuals.

The Non-Thyroidal-Illness-Syndrome is made up of several components, which do not always have to occur at the same time. There are three main components and a few additional components. Even the main components can appear both individually and in combination.

There is talk of a characteristic allostatic constellation of the thyrotropic control loop. An allostatic constellation describes an adaptation of the body to chronic stress. The main components of non-thyroidal illness syndrome include central hypothyroidism (low-THS syndrome), impaired binding of thyroid hormones to the corresponding plasma proteins and reduced formation of T3 from T4 with increased conversion of T4 into rT3 (low- T3 syndrome).

The first component describes a general lack of thyroid hormones, which also occurs with an underactive thyroid gland. Furthermore, the existing thyroid hormones are limited in their effect due to the disturbed binding to the plasma proteins. In addition, the conversion of thyroxine (T4) into the more potent triiodothyronine (T3) is hindered by deiodination in favor of its conversion into the inactive rT3.

Like T3, the molecule rT3 contains three iodine atoms. However, it is inversely iodinated to T3 and is therefore inactive. Other components include impaired uptake of thyroid hormones into target cells and reduced effectiveness of thyroid hormone receptors.

Progressive forms such as low-T4 syndrome, low-T3-low-T4 syndrome, high-T4 syndrome or high-T3 syndrome occur very rarely in non-thyroidal illness syndrome. However, it is difficult to identify the individual components of the syndrome.


The causes and pathogenesis of non-thyroidal illness syndrome are also not fully known. Inflammatory processes that can occur as part of various diseases are discussed for the reduced conversion of T4 into T3. Proinflammatory cytokines, glucocorticoids and certain metabolic metabolites are said to be responsible for these processes.

Damage to the liver parenchyma as part of a corresponding underlying disease may also lead to inhibition of deiodination. Damage to the liver parenchyma could also be the reason for the reduced binding of thyroid hormones to plasma proteins simply because fewer albumins are present.

Endocrine causes such as reduced leptin levels or bacterial endotoxins are considered to be the causes of central hypothyroidism. These influences could trigger local hyperdeiodination, which in turn reduces the production of TRH via the endocrine regulatory circuit. TRH (thyrotropin-releasing hormone) is formed in the hypothalamus and sets the target value for the concentration of thyroid hormones.

When less TRH is present, less thyroid hormone is produced. The increased formation of rT3 instead of T3 may serve to accumulate halogens, including iodine, in the immune cells in order, among other things, to be able to perform better defense work in the event of sepsis .

Serious conditions that can trigger non-thyroidal illness syndrome include cirrhosis of the liver, cardiac insufficiency, myocardial infarction, chronic kidney failure, diabetic ketoacidosis, sepsis or burns. Fasting states, malnutrition or malnutrition in the context of anorexia nervosa can also cause non-thyroidal illness syndrome.

Symptoms, Ailments & Signs

The symptoms of this syndrome are difficult to recognize because they occur in the context of other serious underlying diseases. As a rule, the symptoms are similar to those of hypothyroidism. The metabolism is greatly reduced, so that all bodily functions run on the back burner. It is possible that the organism protects itself from overload in order to be able to cope with the other challenges of the underlying diseases.

Diagnosis & course of disease

The diagnosis of non-thyroidal illness syndrome is usually very difficult. Since it is superimposed by the symptoms of the corresponding underlying disease, only the hormone levels of the free thyroid hormones can provide clues. The basal hormone levels of FT4, FT3 and TSH are usually low, with a large gray area. The concentration of rT3 is usually increased.


As a rule, non-thyroidal illness syndrome itself is a complication. This complaint can be difficult to recognize because the symptoms and complaints are relatively unspecific and not particularly characteristic. However, those affected suffer from the symptoms of hypothyroidism. This leads to permanent tiredness and exhaustion of the patient.

The resilience of those affected also decreases significantly with the non-thyroidal illness syndrome, so that heavy physical activities or sporting activities are usually no longer possible. As a result, the quality of life of those affected is significantly restricted and reduced by the non-thyroidal illness syndrome. Various infections and inflammations can no longer be properly fought off by the body, so that infections and inflammations can occur more frequently.

The treatment of non-thyroidal illness syndrome is usually carried out with the help of thyroid hormones. There are no particular complications for the patient. However, most of those affected are dependent on lengthy therapy, since the disease cannot be completely curtailed. However, the life expectancy of those affected is not reduced by the non-thyroidal illness syndrome. However, the further course of this disease also depends heavily on the underlying disease.

When should you go to the doctor?

If hormonal problems occur or general illnesses such as fever or gastrointestinal problems occur again and again, a doctor should be consulted. Non-specific signs of illness that occur over months or years can indicate non-thyroidal illness syndrome. These are serious changes in the thyroid hormone metabolism, which must be clarified by a doctor in any case. Medical advice is required at the latest when signs of a disease of the internal organs are noticed.

Non-thyroidal illness syndrome often occurs after surgery or in connection with malnutrition and malnutrition. People who regularly take medication or have suffered physical trauma are also among the risk groups and should see their family doctor if the symptoms described appear. If you experience dizziness, tachycardia or severe discomfort, contact the medical emergency service. If in doubt, the person concerned must be taken to a hospital. Non-thyroidal illness syndrome is treated by a thyroid doctor. An internist can do thisor be a specified medical specialist. The individual symptoms can be examined and treated by the responsible specialists in consultation with the family doctor.

Treatment & Therapy

Therapy for non-thyroidal illness syndrome is very controversial. The question arises as to whether general replacement therapy with thyroid hormones makes sense or is even harmful. The body suffers from an undersupply of energy. But that could be the purpose of the changed metabolism of the thyroid hormones in the severity of the underlying disease.

The organism should be protected from overload. Studies have shown that thyroid hormone substitution improves patients’ cardiac output, but not their chances of survival. Non-thyroidal illness syndrome can only be successfully treated as part of the treatment of the underlying disease.

Outlook & Forecast

Non-thyroidal illness syndrome is not a disease in its own right. Therefore, no general prognosis can be made for further health development. The overall situation of the patient and the underlying disease must be considered in order to provide an outlook on future health changes.

The syndrome is detected only in people who have serious medical conditions. Severe organic damage is often already present, which entails an unfavorable prognosis. The quality of life is limited and the patient may need intensive medical care or long-term therapy.

In most cases, recovery is only achieved with great effort and an immense change in living conditions. If the underlying disease cannot be treated successfully, the patient is at risk of premature death. An overall alleviation of the symptoms is only observed if this leads to an improvement in the general state of health with the medical possibilities.

In the case of irreversible organ damage, there is often a need for a donor organ so that changes can take place. Transplantation is associated with other serious complications and side effects. If everything goes without significant disturbances, an improvement in health is possible. Even if the course of the disease is favorable, patients must undergo regular check-ups. The metabolic system and the general functioning of the organs must be examined. Long-term medical support is often necessary.


Since non-thyroidal illness syndrome is not an independent disease, there can be no recommendation for its prevention. However, the risk of the occurrence of the individual underlying diseases can generally be prevented by a healthy lifestyle with a balanced diet, physical activity and abstinence from alcohol and smoking.


In most cases, those affected with non-thyroidal illness syndrome have only a few or limited follow-up measures available. First and foremost, the patient’s state of hunger must be ended. Only then can recovery take place, although complete healing is not always possible.

Therefore, a doctor should be contacted immediately in the case of non-thyroidal illness syndrome, so that the symptoms do not worsen further or, in the worst case, death of the affected person. These are usually dependent on the intake of various preparations or drugs. It is always important to ensure the correct dosage and also to take it regularly in order to alleviate the symptoms.

All doctor’s instructions should be followed. Furthermore, regular checks and examinations of the thyroid gland are very important in non-thyroidal illness syndrome. The further course of the disease depends very much on the time of diagnosis and the severity of the symptoms, so that a general prediction is not possible. However, in some cases, the life expectancy of those affected is reduced by this disease.

You can do that yourself

This disease always occurs in connection with other, sometimes serious diseases that must be treated first and foremost. The affected patients can try to help keep the consequences of their non-thyroidal illness syndrome as low as possible.

For example, it is advisable to maintain a normal body weight and lose excess weight. There are several diet options that must be discussed with the doctor who is also treating the underlying disease. Since non-thyroidal illness syndrome makes it harder to fight off infections, a strong immune system is important. Eighty percent of all immune cells are located in the intestine, so care should be taken to ensure a healthy intestinal flora. This is not only possible with a fresh, low-fat, high-fiber diet, but also with as much exercise as possible, a regular daily routine and fixed sleeping times.

Taking probiotics has also been shown to help. These are living microorganisms that are settled in the intestines via oral intake, where they multiply and should contribute to the development of healthy intestinal flora. High-dose probiotics are available over the counter in pharmacies.

It may be very stressful for the patient to suffer from both an underlying disease and a non-thyroidal illness syndrome, especially since the latter also dampens the joy of movement. This group of patients could find relief with accompanying psychotherapy.