The butterfly-shaped thyroid gland absorbs iodine from the blood and uses it to produce vital hormones for the body’s metabolism. Hyperthyroidism or hypothyroidism throws this interaction out of balance. Read more about the causes, symptoms and treatment of hypothyroidism or hyperthyroidism here.
Tasks of thyroid hormones
The thyroid hormones triiodothyronine and thyroxine have important functions in the body. They increase basal metabolic rate, which increases cardiac work, body temperature, and oxygen consumption in tissues. They increase sensitivity to the stress hormone adrenaline and support protein build-up in the muscles. They also promote growth and maturation of the central nervous system, which is particularly important during pregnancy and childhood. Like other hormones, their production is subject to a control loop. If their concentration in the blood is too low, the upper regulatory authority in the hypothalamus of the brain sends the messenger substance TRH to the pituitary gland, which releases another hormone, thyrotropin (TSH). After about 10 seconds, this reaches the thyroid gland with the message to produce hormones or to release into the blood hormones already stored in the depots of the 3 million thyroid follicles. The organization of this process in the thyroid gland 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 is involved in the regulation of blood calcium levels, along with several others.
Thyroid function: enough, too much, not enough hormones
There are a variety of diseases or changes that affect thyroid activity. For example, acute or chronic inflammation, enlargement of the thyroid gland (goiter, or goiter), autoimmune diseases such as Graves’ disease or Hashimoto’s thyroiditis, or cancers of the thyroid gland itself can affect its function. However, disorders in the control centers, such as those caused by a brain tumor, can also affect the thyroid gland.
- Hyperthyroidism: the cause of increased production and secretion of thyroid hormones almost always lies in the thyroid gland itself. Sometimes districts develop in it at one point or diffusely that produce hormones independently of the control circuit (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 amount of hormones. Another fairly common cause is Graves’ disease, an autoimmune disorder in which substances are produced in the body that act like TSH, encouraging the thyroid to produce regardless of need. Also at the onset of thyroiditis, as a result of a thyroid tumor or an overdose of thyroid hormone tablets (which, dangerously, are sometimes taken as laxatives) can cause an overproduction of thyroid hormones.
- Hypothyroidism: deficiency of thyroid hormones may be congenital (cretinism), due to maternal iodine deficiency during pregnancy or a defective thyroid gland layout. Inflammation, surgery and radioiodine therapy of the thyroid gland as well as medication can also lead to hypothyroidism. In certain brain tumors, the secretion of thyrotropin and thus of thyroid hormones may be reduced. Such disorders, where the cause is not directly in the thyroid gland itself, are also called secondary hypothyroidism.
How do functional disorders manifest themselves?
It is obvious that complaints and symptoms come from the increased or lack of hormone effects. In hyperfunction, the normal effects of T increase.
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and T
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to an unhealthy extent; opposite effects occur with hypofunction. The effects are varied, but nonspecific and often less pronounced in old age.
- Hyperthyroidism: in many affected individuals, the thyroid gland is enlarged. A rapid and irregular pulse, trembling of the hands, sensitivity to heat, and a tendency to sweat are typical. The skin tends to be warm and moist, and as a sign of increased metabolic activity, bowel movements are frequent and soft, there is weight loss despite an increase in appetite, and hair loss.The muscles may ache, and women often experience menstrual irregularities. Those affected are nervous and irritable and suffer from insomnia. If Graves’ disease is the cause, visual disturbances and eye changes (“staring eyes” with protruding eyes) may also occur.
- Hypothyroidism: deficiency of thyroid hormones causes slowed pulse and heart enlargement, sensitivity to cold, decreased appetite, and weight gain. Skin is cool and dry, hair becomes thin and shaggy, voice hoarse and rough. Blood cholesterol levels are often elevated. Menstrual irregularities may also occur. Affected individuals often appear slowed and lethargic or depressed, which can lead to misdiagnosis, especially in the elderly. Congenital hypothyroidism causes intelligence disorders and developmental delays, gait and posture disorders, short stature, and facial malformations. The babies are lazy to drink and move and suffer from constipation. This clinical picture has fortunately become quite rare in industrialized countries due to monitoring and iodine administration during pregnancy, as well as the screening TSH test at the early detection examination after birth.
How is the diagnosis made?
First, the doctor will take the medical history and palpate the thyroid gland to check whether it is enlarged or nodular changes. Ultrasound provides further information on the size and condition, and a tissue sample may also be taken. It is important to check for hormonal changes in the blood. Depending on the suspected cause, other hormones and possibly their release after stimulation as well as antibodies against the thyroid tissue can also be determined in the blood. Metabolic activity and function of the thyroid gland can be assessed by scintigraphy, in which radioactively labeled substances are injected and their deposition in the thyroid tissue is recorded with special cameras and displayed in color.
What therapy is available?
- Treatment of hyperthyroidism depends on the underlying cause. Options include medications that inhibit function (thyrostatic agents), surgery, for example, removal of affected areas, or radioiodine therapy, in which radioactively treated iodine is given that causes thyroid tissue to die.
- In hypothyroidism, artificial thyroid hormones in tablet form must be taken for life. It is started with a small dose, which is slowly increased. If the hormone levels in the blood have normalized, the patient must present once a year to his doctor.
Adequate therapy and good adjustment of hormones is extremely important in both syndromes. 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 care. Therefore, affected individuals should take their medications reliably and see their physician regularly.
How can we prevent it?
To prevent thyroid enlargement due to iodine deficiency, it is important to get enough iodine in the diet. Iodized salt and sea fish are good sources. Possibly, iodide can also be taken in the form of tablets, especially during pregnancy and breastfeeding. However, you should clarify this with your doctor.
