The adrenal glands are small, paired endocrine organs that produce and regulate hormones like adrenaline, aldosterone, and cortisol. An adrenal tumor is an abnormal growth of cells that forms in one or both glands, which can be non-cancerous or cancerous. Understanding the tumor’s location is important because its specific position dictates the type of cells involved, the hormones potentially affected, and the nature of the growth.
The Adrenal Glands’ Position in the Body
The two adrenal glands, also known as suprarenal glands, are situated deep within the abdomen in the retroperitoneal space. They are positioned superior to the kidneys, sitting atop them like small, triangular or crescent-shaped caps. Each gland is small, measuring about 2 inches long and 1 inch wide, and weighing approximately 4 to 5 grams.
Their position places them in close proximity to major blood vessels and organs. The right adrenal gland, which is typically pyramidal, sits beneath the liver and posterior to the inferior vena cava. The left adrenal gland, which is more crescent-shaped, is positioned medial to the spleen and lateral to the abdominal aorta. This deep, central location means they are heavily reliant on the body’s major vascular network for rapid hormone delivery.
The glands are encased within the renal fascia, which anchors them to the diaphragm and the upper pole of the kidney. This anatomical relationship is why they are referred to as suprarenal, meaning “above the kidney.” Their small size and placement make them challenging to access surgically, requiring precise localization when a tumor is present.
Internal Structure: The Cortex and Medulla
Each adrenal gland is composed of two distinct regions: the outer adrenal cortex and the inner adrenal medulla, which differ in structure and function. The outer cortex is the larger layer, making up 80% to 90% of the gland’s mass, and produces steroid hormones. The inner medulla is composed of modified nervous tissue and produces catecholamines.
The adrenal cortex is organized into three separate layers, or zones, each synthesizing specific hormones. The outermost layer, the zona glomerulosa, secretes mineralocorticoids, primarily aldosterone, which regulates blood pressure and the balance of salt and water. Moving inward, the middle and thickest layer is the zona fasciculata, which produces glucocorticoids, mainly cortisol, involved in metabolism and the body’s stress response.
The innermost layer of the cortex is the zona reticularis, which synthesizes a small amount of sex hormones, specifically androgens. These three cortical layers rely on cholesterol as a precursor for steroid hormone synthesis. In contrast, the adrenal medulla is composed of specialized neuroendocrine chromaffin cells. These cells secrete epinephrine (adrenaline) and norepinephrine (noradrenaline), which are released rapidly in response to acute stress to initiate the “fight or flight” response.
Pinpointing the Tumor: Location Determines Type
The specific origin of abnormal cell growth dictates the type of adrenal tumor that forms and the hormones it might overproduce. Tumors arising in the adrenal cortex are the most common and are classified as either adenomas (non-cancerous) or adrenocortical carcinomas (cancerous). Functional adenomas can cause serious health issues by producing an excess of hormones.
A tumor originating in the outermost layer, the zona glomerulosa, is often called an aldosteronoma. This causes an overproduction of aldosterone, leading to Conn’s syndrome (primary hyperaldosteronism). Excessive aldosterone causes the body to retain sodium and water while losing potassium, often resulting in severe, difficult-to-control high blood pressure.
Tumors originating in the middle cortical layer, the zona fasciculata, result in the overproduction of cortisol. These tumors lead to Cushing’s syndrome, characterized by symptoms such as rapid weight gain in the face and trunk, thinning skin, and muscle weakness. The malignant form, adrenocortical carcinoma (ACC), is rare but aggressive, often producing cortisol or multiple hormones.
Tumors that develop in the inner core of the gland, the adrenal medulla, arise from chromaffin cells. The most common tumor here is a pheochromocytoma, which can be non-cancerous or, less frequently, malignant. A pheochromocytoma causes chromaffin cells to secrete excessive amounts of catecholamines, specifically epinephrine and norepinephrine. This hormonal surge results in episodes of extremely high blood pressure, rapid heart rate, headaches, and sweating, reflecting an overactive stress response. Precise localization is paramount for diagnosis, as it predicts which hormones will be affected and the resulting clinical syndrome.