The butterfly-shaped thyroid absorbs iodine from the blood and produces vital hormones for body metabolism. An over- or under-function of the thyroid brings this interaction out of balance. Read more about the causes, symptoms and treatment of hyperthyroidism or thyroid hyperfunction.
Tasks of thyroid hormones
The thyroid hormones triiodothyronine and thyroxine have important functions in the body. They increase the basal metabolic rate, which increases cardiac work, body temperature and oxygen consumption in the tissues. They increase the sensitivity to the stress hormone adrenaline and support the protein build-up in the muscles. In addition, growth and maturation of the central nervous system are promoted, which is particularly important in pregnancy and childhood.
Their production is - like other hormones - a loop. If their concentration in the blood is too low, the upper regulatory agency in the hypothalamus of the brain sends the messenger TRH to the pituitary gland, which releases another hormone, the thyrotropin (TSH). After about 10 seconds this reaches the thyroid gland with the message to produce hormones or to release already existing hormones stored in the depots of the 3 million thyroid follicles into the blood.
Organizing this process in the thyroid takes about 20 minutes, then the thyroid hormones in the blood are on their way to their destinations. Another hormone produced in the thyroid gland is calcitonin, which, in addition to some others, is involved in the regulation of blood calcium levels.
Thyroid function: enough, too much, too little hormones
There are a variety of diseases or changes that affect the thyroid activity. For example, acute or chronic inflammation, enlargement of the thyroid (goiter, or goiter), autoimmune diseases such as Graves' disease or Hashimoto's thyroiditis, or cancers of the thyroid itself can affect their function. But also disturbances in the control centers, for example by a brain tumor, can affect the thyroid gland.
- Hyperthyroidism (Hyperthyroidism): The cause of increased production and release of thyroid hormones is almost always in the thyroid gland itself. Sometimes it develops in one place or diffuse areas that produce hormones independently of the regulatory cycle (thyroid autonomy). If these areas are too large or too active, the down-regulation of the healthy areas is no longer sufficient to compensate for the increased accumulation of hormones.
Another common cause is Graves' Disease, an autoimmune disease that produces substances in the body that act like TSH, encouraging the thyroid to produce whatever the need. Even at the onset of thyroiditis, as a result of a thyroid tumor or overdose of thyroid hormone tablets (which are sometimes taken dangerously as a laxative), overproduction of thyroid hormones can occur.
- Thyroid hypofunction (hypothyroidism): A lack of thyroid hormones may be congenital (cretinism), due to maternal iodine deficiency during pregnancy or a faulty thyroid gland. Also, inflammation, surgery and radioiodine therapies of the thyroid and drugs can lead to hypofunction. In certain brain tumors, the secretion of thyrotropin and thus of the thyroid hormones may be reduced. Such disorders, where the cause is not directly in the thyroid itself, are also called secondary hypothyroidism.
How do dysfunctions manifest themselves?
It is obvious that symptoms and symptoms are caused by the increased or non-existent hormone effects. In the case of hyperfunction, the normal effects of T 3 and T 4 increase to an unhealthy extent, in the case of underfunction, adverse effects occur. The effects are varied, but non-specific and often less pronounced in old age.
- Hyperthyroidism: In many sufferers, the thyroid is enlarged. Typical are a fast and irregular pulse, shaking of the hands, sensitivity to heat and a tendency to sweat. The skin is rather warm and moist, and as a sign of increased metabolic activity, the bowel movement is frequent and soft, it comes to weight loss despite appetite increase and hair loss. Muscles can hurt, and women often experience cycle disorders. Those affected are nervous and irritable and suffer from insomnia. If a Graves' Disease is the cause, also visual disturbances and eye changes ("gaze" with protruding eyes) can occur.
- Thyroid hypofunction: A lack of thyroid hormones leads to slowed pulse and heart enlargement, hypersensitivity, decreased appetite and weight gain. The skin is cool and dry, the hair is thin and shaggy, the voice hoarse and rough. Often, blood cholesterol levels are elevated. Again, there may be menstrual disorders. Those affected often appear slowed and sluggish or depressed, which can lead to a misdiagnosis, especially in the elderly.
Congenital hypothyroidism causes disorders of intelligence and developmental delays, gait and posture disorders, short stature and facial malformations. The babies are lazy and motionless and suffer from constipation. Fortunately, this disease has become quite rare in industrialized countries due to surveillance and iodine in pregnancy, as well as the screening TSH test in postpartum screening.
How is the diagnosis made?
First, the doctor will raise the medical history and scan the thyroid gland to see if it is enlarged or nodularly altered. Further statements on the size and condition of the ultrasound provides, possibly it can also take a tissue sample.
Important is the examination for hormone changes in the blood. Depending on the suspected cause, further hormones and possibly their release after stimulation as well as antibodies against the thyroid tissue can be determined in the blood. Metabolic activity and thyroid function can be assessed by means of scintigraphy, in which radioactively labeled substances are injected and their deposition in the thyroid tissue is recorded with special cameras and displayed in color.
Which therapy is there?
- The treatment of hyperthyroidism depends on the underlying cause. Options include drugs that inhibit function (antithyroid drugs), operations such as the removal of affected areas or the radioiodine therapy, which is given radiolabeled iodine, which leads to the death of thyroid tissue.
- In the case of hypofunction, artificial thyroid hormones in tablet form have to be taken for life. It starts with a low dose, which is slowly increased. Once the hormone levels in the blood have normalized, the patient has to introduce himself to his doctor once a year.
Sufficient therapy and good adjustment of the hormones is extremely important in both diseases. Otherwise, in certain situations, such as serious illness or surgery, a life-threatening condition can occur ("thyrotoxic crisis" or "myxedema coma"), which can lead to death even under intensive medical care. Therefore, sufferers should take their medication reliably and visit their doctor regularly.
How to prevent?
In order to prevent thyroid enlargement due to iodine deficiency, a sufficient supply of iodine via the diet is important. Iodine salt and sea fish are good sources. Possibly. iodide can also be taken in the form of tablets, especially during pregnancy and lactation. However, you should check with your doctor.