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Functional state of the sympathoadrenal system
Last reviewed: 05.07.2025
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Like the posterior pituitary gland, the adrenal medulla is a derivative of nervous tissue. It can be considered a specialized sympathetic ganglion. Clusters of chromaffin tissue are found in the sympathetic nervous system (paraganglia). A chain of chromaffin bodies is located anterior to the abdominal aorta, at the aortic bifurcation; the carotid bodies are also part of the chromaffin system of the body.
Chromaffin cells of the adrenal glands secrete mainly adrenaline and to a lesser extent norepinephrine, whereas postganglionic cells of the sympathetic nervous system secrete predominantly norepinephrine.
The similarity of the products and response modes of the sympathetic nervous system and the adrenal medulla became the basis for combining these structures into a single sympathoadrenal system with the isolation of its nervous and hormonal links.
Chromaffin cells and sympathetic ganglion cells are formed during embryogenesis from cells of the embryonic neural crest called sympathogonia. These cells serve as precursors of sympathoblasts (from which sympathetic ganglion cells develop) and pheochromoblasts (which give rise to chromaffin cells). Pheochromocytoma may develop from chromaffin cells. Other types of catecholamine-producing tumors arise from other neural crest cells:
- from sympathoblasts - sympathoblastoma;
- from pheochromoblasts - pheochromoblastoma;
- from the cells of the sympathetic ganglion - ganglioneuroma.
Tumors of the first two types are called neuroblastomas, the third - ganglioneuroma (ganglioneuroblastoma). These types of tumors are observed in newborns and young children, and very rarely in adults. Neuroblastomas are most often detected at the age of 1-3 years, these are very malignant tumors. At least 50% of these tumors are localized in the abdominal cavity (up to 35% - in the adrenal glands). Ganglioneuroblastoma is formed by the transformation of neuroblastoma cells, contains both neuroblasts and ganglion cells at different stages of differentiation. Ganglioneuroma is a benign tumor consisting of mature ganglion cells.
In adults, the most common tumor is pheochromocytoma, which is formed from chromaffin cells. In 90% of cases, the catecholamine-producing chromaffin tumor is localized in the adrenal medulla, and in 10% - outside these glands. Less than 10% of pheochromocytomas are malignant.
In chromaffin tumors of the adrenal and extra-adrenal localization, a large amount of adrenaline and noradrenaline enters the bloodstream. This causes hypertensive crises against the background of normal arterial pressure (paroxysmal form of the disease), persistently elevated arterial pressure and periodically recurring even greater pressure increase against this background (mixed form); persistent arterial hypertension without crises (constant form).
A whole range of indicators are used to assess the functional state of the sympathoadrenal system. However, only some of these markers are used in clinical practice, mainly for the diagnosis of pheochromocytoma. Approximately 1 in 200 patients with high blood pressure is diagnosed with pheochromocytoma.
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