Unexpected adrenal gland discoveries in medical imaging - understanding their evaluation, management, and clinical significance based on the latest European Society of Endocrinology guidelines.
Imagine you undergo a CT scan for a minor issue, only to have your doctor inform you that they've found something unexpected: a lump on one of your adrenal glands. This surprise discovery, happening to millions worldwide, is what doctors call an adrenal incidentaloma. These unexpected findings have become increasingly common in our modern era of detailed medical imaging, with studies showing they appear in 1% to 5% of all abdominal CT scans performed for unrelated reasons 1 .
Adrenal incidentalomas are found in over 10% of elderly individuals, with peak occurrence between 50-60 years of age 1 .
The term might sound alarming, but here's the reassuring truth: the vast majority of these adrenal masses are benign and require no treatment. However, a small but significant number can be hormonal powerhouses secreting excess cortisol or catecholamines, or in rare cases, malignant tumors requiring immediate attention. This medical detective story of separating harmless findings from potentially dangerous conditions represents one of endocrinology's most fascinating challenges. Thanks to recent international collaboration between the European Society of Endocrinology and the European Network for the Study of Adrenal Tumours, we now have clear guidelines to navigate this complex medical territory 2 3 .
Your adrenal glands are small, triangular-shaped organs sitting atop your kidneys, functioning as your body's built-in stress managers. They produce crucial hormones including cortisol (which helps regulate metabolism and stress response), aldosterone (which controls blood pressure), adrenaline (the "fight-or-flight" hormone), and small amounts of sex hormones 1 .
An adrenal incidentaloma is defined as an adrenal mass 1 centimeter or larger that's discovered unexpectedly during imaging performed for reasons unrelated to suspected adrenal disease 1 .
When an incidentaloma is discovered, it could represent several different types of growths:
Most common type - typically harmless
Produce excess cortisol without obvious symptoms
Catecholamine-producing tumors
Rare malignant tumors requiring immediate attention
This diverse spectrum explains why a systematic approach to evaluation is crucial—while most incidentalomas are harmless "bystanders," some can significantly impact health through hormone excess or malignant potential.
When an adrenal incidentaloma is discovered, the first step is typically a specialized imaging assessment. The 2023 European Society of Endocrinology guidelines provide clear direction: each adrenal mass requires dedicated adrenal imaging 3 .
The initial test is usually a non-contrast CT scan, which measures the tissue density in Hounsfield Units (HU). This simple measurement provides powerful insights:
| Imaging Feature | Hounsfield Units (HU) | Malignancy Risk | Recommended Action |
|---|---|---|---|
| Homogeneous, lipid-rich | ≤ 10 | Very low | No further imaging needed |
| Intermediate density | 10-20 | Low | Consider additional imaging or follow-up |
| High density, irregular | > 20 | Elevated | Discuss in multidisciplinary meeting; possible surgery if >4cm |
| Hormone | Screening Test | Critical Value | Who to Test |
|---|---|---|---|
| Cortisol | 1-mg overnight dexamethasone suppression test | Serum cortisol >50 nmol/L (>1.8 µg/dL) | All patients |
| Catecholamines | Plasma-free metanephrines | 2-3 × upper limit of normal | All patients |
| Aldosterone | Aldosterone-to-renin ratio (ARR) | ARR >20 (ng/dL)/(ng/mL/h) | Patients with hypertension or hypokalemia |
| Androgens | Testosterone, DHEAS, androstenedione | Laboratory-specific | Suspicious features on imaging or clinical signs |
Simultaneously with imaging, a thorough hormonal evaluation is essential since functional tumors (those producing excess hormones) typically require surgical removal regardless of their imaging characteristics 1 3 .
The standard hormonal workup includes:
Modern adrenal research relies on sophisticated laboratory techniques to unravel the mysteries of these tumors. Here are some essential tools from the researcher's toolkit:
Precise measurement of multiple hormone levels simultaneously
Creating steroid hormone profiles from plasma or urine; considered gold standard for hormone assessment 4
Comprehensive analysis of genetic variations across multiple genes
Identifying germline and somatic mutations in pheochromocytomas, ACC, and familial endocrine syndromes 4
One of the most significant advances in the 2023 guidelines is the refined approach to what was previously called "subclinical Cushing's syndrome." The guidelines now use the term mild autonomous cortisol secretion (MACS) and provide stronger evidence for its clinical importance 3 .
MACS is defined by serum cortisol levels >50 nmol/L (>1.8 µg/dL) after a 1-mg dexamethasone suppression test in patients without typical physical signs of overt Cushing's syndrome. Recent research has demonstrated that these patients harbor increased risk of morbidity and mortality, particularly from cardiovascular diseases and metabolic complications like hypertension and type 2 diabetes 3 .
The guidelines recommend that all patients with MACS should be screened for cortisol-related comorbidities such as hypertension, diabetes, osteoporosis, and obesity. For those with relevant complications, surgical treatment (adrenalectomy) should be considered through an individualized approach weighing potential benefits against surgical risks 3 .
This personalized decision-making considers factors including the degree of cortisol excess, severity of comorbidities, patient age, general health status, and importantly, patient preferences.
Patients with MACS should be evaluated for the following comorbidities:
Hypertension, heart disease
Type 2 diabetes, insulin resistance
Bone density loss, fracture risk
The decision to proceed with surgery involves careful consideration of multiple factors:
Based on imaging features (size >4 cm, inhomogeneous appearance, HU >20) 3
Which carries increased malignancy risk 1
On follow-up imaging 1
Including age, general health, and preferences 3
For masses with benign imaging characteristics (HU ≤10) that are nonfunctioning and smaller than 4 cm, surgery is not routinely indicated 3 .
For patients who don't undergo immediate surgery, a structured follow-up approach is recommended:
(HU ≤10) typically require no specific follow-up 3 .
May warrant repeat imaging in 6-12 months to assess stability 1 .
Should receive regular monitoring and management of cortisol-related comorbidities such as hypertension, diabetes, and osteoporosis 3 .
Understanding when surgery might be recommended based on tumor size and characteristics:
Research in adrenal tumors is advancing rapidly, with several promising directions:
Supported by artificial intelligence are revealing new molecular patterns in adrenal tumors 4 .
Enables more precise hormone profiling, moving beyond traditional tests 4 .
Have discovered that up to 35-40% of pheochromocytomas have germline genetic variants, highlighting the importance of genetic counseling in selected cases 4 .
The discovery of an adrenal incidentaloma can understandably cause anxiety, but the collaboration between the European Society of Endocrinology and the European Network for the Study of Adrenal Tumours has created a clear roadmap for managing these findings. Through systematic imaging assessment, thorough hormonal evaluation, and personalized decision-making, clinicians can now confidently distinguish between harmless incidental findings that require no intervention and significant pathology needing treatment.
As research continues to unravel the molecular secrets of adrenal tumors, we can expect even more refined diagnostic approaches and targeted therapies. For now, the comprehensive guidelines provide reassurance that medicine has robust tools to ensure these unexpected discoveries receive the appropriate attention they deserve—neither underestimating potential risks nor overtreating inconsequential findings.