Blood & Laboratory Values

Catecholamines – Function & Diseases

Catecholamines

Catecholamines are biogenic amines and play important roles as neurotransmitters and hormones . The best-known substances from this group are the stress hormones adrenaline and noradrenaline . If the adrenal medulla is underactive , there is an undersupply of catecholamines, which is accompanied by fainting spells .

What are catecholamines?

Catecholamines are biogenic amines that appear in particular as neurotransmitters. They originate from the endocrine glands of the adrenal medulla and are produced with the participation of the sympathetic nervous system . They bind to the so-called alpha and beta receptors and show a stimulating effect on the circulation. The best-known representatives of this group are the stress hormones adrenaline, noradrenaline and dopamine .

Catecholamines have prompt activity as stress hormones because of their binding to the alpha and beta receptors. This distinguishes them from glucocorticoids such as cortisol , which do not take effect quickly enough in the event of sudden, short-term stress. Adrenaline was the first hormone to be extracted, researched, and man-made. Catecholamines are mimicked by many drugs and are used in intensive care medicine to treat shock and allergic reactions .

Anatomy & Structure

The catecholamines are involved in biosynthesis. The biosynthesis of these substances occurs in the adrenal medulla and in the catecholaminergic nerve cells . The amino acid tyrosine is first converted to levodopa by the enzyme tyrosine hydroxylase. The aromatic L-amino acid decarboxylase converts this levodopa into dopamine. In dopamine beta-hydroxylase, dopamine is converted to norepinephrine when needed. 

Norepinephrine can become adrenaline through methylation. This last conversion is catalyzed by phenylethanolamine N-methyltransferase. Catecholamines can also be inactivated. This inactivation corresponds to uptake into the cells and degradation of the substances by catechol-O-methyltransferase or monoamine oxidase. Due to their structure, the catecholamines stimulate the alpha 1 and beta receptors in the heart , bronchi , gastrointestinal tract and blood vessels .

Function & Tasks

Catecholamines are secreted in the adrenal medulla by action of the sympathetic nervous system. They should ensure survival in the event of sudden stress . Due to evolution, flight and fight are among the most important survival strategies. For both strategies, the body needs an excess of energy. This energy is provided by catecholamines. They show effects on the circulatory system, have a stabilizing effect and enable people to go beyond their limits.

Catecholamines decentralize and thus ensure that the heart and internal organs are still supplied with blood even in the event of blood loss. All catecholamines act on G protein-coupled receptors. These receptors are either adreno- or dopamine receptors and are found in both the vascular system and internal organs. There are significant differences between the effects of individual catecholamines. While some of them stimulate the receptors, others block certain receptors. For example, norepinephrine blocks the renewed release of catecholamines. Adrenaline, on the other hand, increases blood pressure and heart rate. Norepinephrine only increases blood pressure and has little effect on rate.

Dopamine, in turn, has a positive effect on the contraction force of the heart. Thus, stimulation of dopaminergic receptors increases renal, cerebral and mesenteric blood flow . On the other hand, when beta-2 receptors are stimulated, the metabolism increases, the vascular resistance decreases and the bronchi and vessels expand. Stimulating the heart’s beta-1 receptors in turn increases heart strength, heart rate, and heart excitability. Gastrointestinal movements are usually throttled by catecholamines. So the effects of catecholamines are numerous and affect the nervous system to the same extent as the metabolic system , the blood system and the cardiovascular system .

Diseases

A rare condition associated with catecholamines is pheochromocytoma . A hormone-producing tumor of the adrenal medulla forms. This is to be distinguished from the paraganglioma . This is a hormone-producing tumor of the sympathetic trunk in the spine . Both tumor diseases can cause similar symptoms, because in both the adrenal medulla produces more adrenaline and noradrenaline. More rarely, there is also an overproduction of dopamine. 

Due to the circulatory stimulating effect of stress hormones, high blood pressure sets in . Rapid heartbeat and sweating are among the most common symptoms. Headaches , tremors and weight loss also occur with this condition. Inner restlessness and panic set in. Due to the increased adrenaline level, the blood sugar also rises and after a certain time can promote diabetes as a secondary disease. In most cases, hormone-producing tumors are benign. The tumors occur mainly in the context of various hereditary diseases , for example in the context of the Hippel-Lindau syndrome.

Hypofunction of the adrenal glands is somewhat more common than hormone-producing tumors of the adrenal medulla . Such hypofunctions can occur, for example, after an operation in the kidney area . Once the body produces too few catecholamines, it becomes difficult to maintain blood pressure. Dizziness attacks with fainting spells set in. Something similar happens in Waterhouse-Friedrichsen syndrome. This is a complete failure of the adrenal glands that is preceded by pneumococcal or meningococcal infection.

While hormone-producing tumors are usually surgically removed, the doctor treats hypofunction of the adrenal medulla by administering catecholamines. The administration of catecholamines also plays a role in the field of emergency medicine and can be necessary here, for example, after resuscitation .

Lisa Newlon
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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.