What is the adrenal gland?
The adrenal gland is a paired organ that produces various hormones. It is about three centimeters long, one and a half centimeters wide and weighs about five to 15 grams. Each adrenal gland is divided into two sections: Adrenal medulla and cortex.
Adrenal medulla
Here inside the organ, important adrenal hormones from the group of so-called catecholamines are produced and released into the blood:
- Adrenaline: has a constrictive effect on the blood vessels, increases the heart rate and blood pressure;
- Noradrenaline: also has a constrictive effect on the blood vessels, but slows down the pulse and increases blood flow to the heart;
- Dopamine: precursor of the two catecholamines mentioned above, but also acts as a hormone itself; has numerous effects (influences mood, increases blood flow to the abdominal organs, etc.)
The cells of the adrenal medulla can be easily stained with chromium salts. For this reason they are called “chromaffin cells”. Other components of the medulla are connective tissue, blood vessels and nerve fibers.
Adrenal cortex
Hormones are also produced in the cortical region (aldosterone, cortisol, androgens = male sex hormones). Read more about this in the article Adrenal cortex.
What is the function of the adrenal gland?
The function of this paired organ is to produce and release various vital hormones.
The release of catecholamines is promoted by acetylcholine, a neurotransmitter of the nervous system. Adrenaline and noradrenaline increase the heart rate and blood pressure, accelerate breathing, widen the airways and prepare the muscles to tense up and react quickly. At the same time, systems that are not needed in these moments (such as the gastrointestinal tract) are shut down.
Where is the adrenal gland located?
There is an adrenal gland on each upper pole of the kidney. The left one is crescent-shaped, the right one is triangular.
What problems can the adrenal gland cause?
There are numerous adrenal gland diseases:
A pheochromocytoma is a mostly benign tumor of the adrenal medulla that releases adrenaline and noradrenaline, and in immature tumor forms (pheochromoblastoma, neuroblastoma) also the precursor dopamine. Patients suffer from seizure-like high blood pressure, headaches, sweating and pale skin (because adrenaline and noradrenaline constrict the blood vessels).
An enlargement or benign or malignant tumors of the adrenal gland can lead to an overproduction of the hormone aldosterone (in the cortical region). Doctors then refer to this as Conn’s syndrome. Those affected have high blood pressure that is difficult to control.
If the cortical region is dysfunctional, too few hormones (aldosterone, cortisol, androgens) are produced here. Addison’s disease (Addison’s disease) develops. Symptoms include brown discoloration of the skin, fatigue, lack of appetite and weight loss, hunger for salty foods, low blood pressure, digestive problems such as nausea and vomiting as well as psychological symptoms such as depression and irritability. Addison’s disease leads to death if left untreated.
In adrenogenital syndrome (AGS), too little cortisol and aldosterone and too much androgens are produced due to an enzyme defect. The affected babies are tired and apathetic. Due to the excess of male sex hormones, the clitoris, penis and testicles are enlarged. Girls become masculine and puberty occurs prematurely.
The medullary region of the adrenal gland is rarely underactive.
