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Adrenaline and noradrenaline in the blood.
Last reviewed: 06.07.2025
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Reference concentrations (norm) in blood plasma: adrenaline - 112-658 pg/ml; norepinephrine - less than 10 pg/ml.
Adrenaline is a hormone of the adrenal medulla. From the adrenal medulla, it enters the bloodstream and affects the cells of distant organs. Its content in the blood depends on the tone of the sympathetic system. In hepatocytes, adrenaline stimulates the breakdown of glycogen and thereby increases the glucose content in the blood. In adipose tissue, adrenaline activates lipase and the process of TG breakdown. Adrenaline activates glycogenolysis in muscle cells. It strengthens heart contractions and increases their frequency, increases blood pressure mainly due to systolic. Adrenaline dilates the vessels of muscles and the heart and constricts the vessels of the skin, mucous membranes and abdominal organs. It plays a large role in the body's response to stressful situations. Under its influence, the productionof ACTH increases, and therefore, corticosteroids. It increases the sensitivity of the thyroid gland to the action of TSH. The concentration of adrenaline in the blood characterizes the humoral part of the sympathetic nervous system.
Unlike adrenaline, noradrenaline enters the blood plasma primarily from the sympathetic nerve endings (most of it is reabsorbed by neurons, and 10-20% enters the blood). Only a very small part of the blood noradrenaline is formed in the adrenal medulla. The action of noradrenaline is associated with a predominant effect on alpha-adrenoreceptors, while adrenaline acts on alpha- and beta-adrenoreceptors. The concentration of noradrenaline in the blood characterizes the activity of neurons of the sympathetic nervous system.
[ Determination of adrenaline and noradrenaline
Determination of adrenaline and noradrenaline is used in clinical practice mainly for the diagnosis of pheochromocytoma and differential diagnosis of arterial hypertension.
In patients with pheochromocytoma, the concentration of catecholamines in the blood increases by 10-100 times. There is no correspondence between the size of the tumor, the concentration of catecholamines in the blood and the clinical picture. Small tumors can synthesize and secrete large amounts of catecholamines into the blood, while large tumors metabolize catecholamines in their own tissue and secrete only a small proportion. Most pheochromocytomas primarily secrete norepinephrine into the blood. In hypertension, the concentration of catecholamines in the blood is at the upper limit of normal or increased by 1.5-2 times. If the concentration of catecholamines in the blood plasma at rest exceeds 2000 μg/l, then the presence of pheochromocytoma should be suspected. Concentrations of 550-2000 μg/l should raise doubts about the presence of a tumor; in such cases, additional studies are necessary, in particular, a clonidine test. The test is based on the ability of clonidine to reduce the tone of the sympathetic nervous system and thus reduce the concentration of norepinephrine in the blood. Blood is taken twice: on an empty stomach and 3 hours after oral administration of 0.3 mg of clonidine. In patients with pheochromocytoma, the concentration of norepinephrine after taking the drug does not change significantly or decreases by less than 50% of the initial level; in individuals with arterial hypertension of other origins and in healthy individuals, the concentration of norepinephrine decreases by more than 50%.
It should be remembered that with adrenal pheochromocytoma, the concentration of adrenaline and norepinephrine in the blood increases, while extra-adrenal pheochromocytomas usually cause an increase in the content of norepinephrine only.
The study of the concentration of catecholamines in the blood and their excretion with urine is important not only for the diagnosis of pheochromocytoma, but also for monitoring the effectiveness of treatment. Radical removal of the tumor is accompanied by normalization of the excretion of these substances, and relapse of the tumor leads to its repeated increase.
The sensitivity of methods for determining the concentration of adrenaline and noradrenaline in the blood for the diagnosis of pheochromocytoma is lower than for their determination in urine.