Hormones are chemical messengers in the body. They regulate many important metabolic processes and are transported with the bloodstream.


hormones Regulate countless body processes - from growth to blood pressure and blood sugar to sexual functions. Read more about the production and function of the hormones, important representatives and the hormone determination in blood and urine.

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  • What are hormones?

  • Classification of hormones

  • Examples of important hormones

  • hormonal balance

  • Measurement of hormone levels

What are hormones?

Hormones are chemical messengers in the body. They transmit information, especially between the brain and the rest of the body, and regulate important processes - from blood sugar levels to water balance and blood pressure to pregnancy.

Many hormones are produced in glandular cells of certain organs and released into the blood. Through the bloodstream they get (sometimes bound to proteins) to their destination - the cells of other organs. On or in the cells are "docking" (receptors) for the hormones. The hormones bind to these and trigger changes in the cell.

Some hormones work within seconds. But most take several minutes or more to cause a reaction. In contrast, signals in the nervous system are transmitted much faster. The nervous system acts directly only on nerve cells, muscles and glands. Hormones, on the other hand, have a much broader effect: they can affect many different functions in many cells of the body.

Classification of hormones

There is a distinction between fat-soluble and water-soluble hormones.

The fat-soluble ones include:

  • Steroid hormones (glucocorticoids, mineralocorticoids, sex hormones)
  • Thyroid hormones (T3 and T4)
  • Nitric oxide (NO)

The water-soluble hormones include:

  • Hormones made from amino acids (epinephrine and norepinephrine, melatonin, histamine, serotonin)
  • Peptides and proteins (e.g., all releasing and inhibiting hormones, oxytocin, ADH, growth hormone, TSH, ACTH, FSH, LH, parathyroid hormone, insulin, gastrin, erythropoietin)
  • Eicosanoids (prostaglandins, leukotrienes)

Examples of important hormones

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Examples of hormones

Brain (hypothalamus, pituitary)


Thyrotropin (TSH)

Luteinizing Hormone (LH)

Growth hormone (GH)








Thyroid and parathyroid glands

Triiodothyronine (T3)

Thyroxine (T4)








Ovaries and testes




hormonal balance

The hormone balance is regulated by complicated, fault-prone feedback systems. Many illnesses in the body can be due to failures of different hormone systems. This can be caused by:

  • Damage to the hormone-forming organ
  • Damage to the target organ
  • Problems with the transport proteins
  • Malignant tumors that produce hormones on their own

The individual hormone systems can be examined by functional tests. It actively intervenes in the hormone system to be tested and monitors whether it reacts accordingly. A simple example: The doctor can administer a sugar solution to a patient. He then measures whether enough insulin is released in response to this, causing the blood sugar level to return to normal levels.

Most other hormonal circuits are far more complex than the insulin system.

Measurement of hormone levels

The hormone concentrations in the blood vary greatly. They can change at an annual rate (such as male testosterone), at monthly rates (such as estrogen in women), at daily rhythms (such as cortisol) or even at hourly rates (such as follicle stimulating hormone = FH). This must be taken into account when measuring hormone levels.

Hormones can be detected in blood serum and urine. Since they have a strong effect, they are present in extremely low concentrations, which is why very sensitive examination methods are required. One such method of investigation is the so-called immunoassay, an antigen-antibody test.

Hormones are only in the blood for a limited time because they are broken down very quickly, for example, by enzymes or heat. Therefore, for some hormones (ACTH, parathyroid hormone, calcitonin), the blood sample should be cooled during the procedure or an enzyme inhibitor added.

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