Environmental Triggers and Risk Factors for Pheochromocytoma

Pheochromocytoma is a rare but treatable tumor that can have significant side effects due to its excessive hormone production. 

While many pheochromocytoma cases are linked to genetic factors, people wonder whether environmental exposures may also play a role in triggering these tumors. 

In this article, we will explore both the environmental and genetic risk factors that can influence the development of pheochromocytoma, focusing on how healthcare providers and patients can use this knowledge for better prevention and management.

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What Is Pheochromocytoma?

Pheochromocytoma is a rare tumor that develops deep in the adrenal glands, which sit above the kidneys. It originates in specialized cells called chromaffin cells within the adrenal glands. 

Chromaffin cells are responsible for producing catecholamines, which are chemicals that can function as both hormones and neurotransmitters.

Most pheochromocytomas are small. Despite their small size, pheochromocytomas can produce excessive amounts of catecholamines, particularly adrenaline (epinephrine) and noradrenaline (norepinephrine). 

These catecholamines regulate blood pressure and the body’s stress response, and overproduction of these hormones can lead to significant health problems.

Pheochromocytomas can be benign (non-cancerous and slow-growing) or malignant (aggressive and spreading to different organs in the body).

While many pheochromocytomas are hereditary and linked to specific genetic mutations, they can also occur sporadically. 

They are most often diagnosed in individuals between the ages of 20 and 40.

Pheochromocytoma development is largely influenced by genetics, and few environmental risk factors have been clearly identified. However, hypoxia is one known environmental risk factor that can increase the likelihood of pheochromocytoma, potentially by enhancing genetic susceptibility.

Key Environmental Triggers for Pheochromocytoma

The only broadly recognized environmental trigger for pheochromocytoma is hypoxia.

Hypoxia

Hypoxia, or low oxygen levels, is strongly linked to the development of pheochromocytomas. 

In people with chronic low oxygen conditions, such as cyanotic congenital heart disease (CCHD), the risk of developing pheochromocytomas and paragangliomas (tumors that, like pheochromocytoma, arise from chromaffin cells, but are found outside of the adrenal glands) is much higher. 

Similarly, people living at high altitudes, where oxygen levels are lower, are more likely to develop head and neck paragangliomas, likely due to similar hypoxia-driven genetic changes.

Hypoxia can be caused by environmental triggers, or by genetic mutations. Many of the genes linked with pheochromocytoma are known to affect tissue oxygenation. 

Hypoxia and Genetic Mutations in Pheochromocytoma

These mutations, particularly in EPAS1 gene, prevent the normal breakdown of a protein called HIF2-alpha, which then promotes tumor growth. 

Research has found that mutations in other genes like SDH and VHL cause abnormal activation of hypoxia-inducible factors (HIFs). 

These HIFs regulate genes that control important processes such as cell growth, survival, energy use, and the development of new blood vessels, all of which can drive tumor growth.

Other Factors that May Affect Hypoxia

Many factors outside of genetics are known to contribute to hypoxia, or decreased oxygen levels. 

While there is currently no research available to directly link these to the development of pheochromocytoma, patients at increased risk for pheochromocytoma may want to minimize their risk from the following:

Chronic lung conditions (e.g., COPD)

• Anemia

• Smoking and second-hand smoke

• Sleep apnea

• Carbon monoxide exposure

• Pulmonary embolism

Environmental toxins (e.g., cyanide, hydrogen sulfide, ammonia, sulfur dioxide, volatile organic compounds like benzene)

• Air pollution 

• Drug overdose (e.g., opioids)

• Sedation and anesthesia

These factors can impair oxygen supply or usage, leading to hypoxia.

Key Environmental Factors that Drive Neuroendocrine Tumors

"Neuroendocrine" refers to cells that have both nerve and hormone-producing functions. 

These cells receive signals from the nervous system and release hormones into the bloodstream, controlling processes like metabolism, stress, and digestion. Neuroendocrine cells are found in organs like the lungs, digestive system, and adrenal glands. 

A pheochromocytoma is one type of neuroendocrine tumor. 

What are Neuroendocrine Tumors (NETs)?

Neuroendocrine tumors (NETs) are cancers that develop from neuroendocrine cells. They can occur in different parts of the body, most commonly in the lungs, digestive system, and pancreas. These tumors can produce hormones that cause various symptoms depending on the type of hormone released. 

NETs can grow slowly or be more aggressive and can be benign or cancerous.

A pheochromocytoma is a type of NET that occurs in the adrenal glands.

What Environmental Risk Factors are Linked with NETs?

Environmental risk factors that contribute to neuroendocrine tumor development include exposure to tobacco smoke, alcohol, and obesity-related metabolic disturbances like diabetes. 

Additional research is exploring the effects of diet and endocrine disruptor exposure on NET development.

While these risk factors are primarily linked with digestive system NETs, these factors suggest that both lifestyle choices and metabolic health can influence the risk of developing neuroendocrine tumors. 

If this is the case, then maintaining a healthy lifestyle and reducing the risk of exposure to known risk factors for hypoxia may benefit people at increased risk of developing pheochromocytoma. 

Genetic and Hereditary Risk Factors for Pheochromocytoma

Genes are much more strongly implicated in the development of pheochromocytoma than environmental factors. Specific genetic mutations put some people at increased risk of developing pheochromocytoma.

Neurofibromatosis Type 1 (NF1)

NF1 is a genetic condition caused by mutations in the NF1 gene located on chromosome 17. It is characterized by skin abnormalities such as café-au-lait spots, neurofibromas, freckling, and Lisch nodules in the eyes. 

While most NF1-related tumors are benign, approximately 1-3% of individuals with NF1 develop pheochromocytomas, typically located in the adrenal glands. Malignant pheochromocytomas in NF1 are rare.

Multiple Endocrine Neoplasia Type 2 (MEN2)

MEN2 is a genetic disorder caused by mutations in the RET gene and has two subtypes: MEN2A and MEN2B. 

The condition is closely associated with Medullary Thyroid Carcinoma (MTC), and around half of those affected also develop pheochromocytomas. These tumors usually occur in the adrenal glands, often on both sides and are rarely malignant.

Von Hippel-Lindau (VHL)

VHL is a hereditary condition caused by mutations in the VHL gene. It can lead to the development of multiple tumor types, including pheochromocytomas, hemangioblastomas, and renal cell carcinoma. 

In VHL type 1, pheochromocytomas are uncommon, whereas VHL type 2 frequently involves pheochromocytomas, typically affecting both adrenal glands. Malignant pheochromocytomas in VHL are uncommon.

Paraganglioma Syndrome Type 4 (PGL4)

Paraganglioma Syndrome Type 4 (PGL4) is linked to mutations in the SDHB gene and is associated with familial pheochromocytoma. 

Individuals with SDHB mutations are more prone to developing tumors outside of the adrenal glands, known as paragangliomas, which have a higher risk of becoming malignant. These tumors tend to occur earlier in life and often exhibit more aggressive behavior.

Early Signs, Symptoms, and Risk Assessment

Identifying high-risk patients through symptom recognition and the appropriate testing is necessary to get patients the care they need.

Symptom Recognition

Symptoms of pheochromocytoma result from excessive catecholamine production by the tumor. For example, norepinephrine is often secreted continuously, causing severe, persistent high blood pressure, while bursts of epinephrine can lead to episodes of tachycardia, anxiety, and palpitations. 

While a rare cause of high blood pressure, pheochromocytoma is important to recognize: pheochromocytoma is the cause of about 0.2% of patients with uncontrolled high blood pressure. 

Common symptoms include:

• Severe or sudden high blood pressure

• Headaches

• Sweating

• Heart palpitations

• Anxiety or panic attack-like feelings

Since these symptoms can come and go, they may be mistaken for more common conditions. Clinicians should consider pheochromocytoma in cases of resistant hypertension, especially when patients show a combination of the above symptoms and/or they continue to have high blood pressure despite multiple medications.

Risk Factors and Screening for Families

If pheochromocytoma runs in a family, genetic counseling and regular screenings are necessary for early detection. Family members with a known genetic mutation should be monitored closely through annual blood tests and imaging to catch any tumors early.

Additionally, a family history of genetic syndromes like MEN2, VHL, or NF1 significantly increases the risk of developing pheochromocytoma. Regular screening and early intervention are recommended for individuals with a family history of these conditions.

Diagnostic Approaches and Treatment Options

When a clinician suspects pheochromocytoma, the first initial test is generally blood or urine tests, or both.

Screening and Diagnostic Tests

Pheochromocytoma diagnosis involves a combination of biochemical testing, imaging scans, and genetic testing to confirm the presence of a catecholamine-secreting tumor and assess any hereditary links.

Biochemical Testing

Doctors first measure catecholamines and their byproducts, called metanephrines, in blood and urine. Elevated levels confirm excess hormone production caused by the tumor. 

To avoid false positives, blood samples should be taken while the patient is lying down, as sitting can artificially raise metanephrine levels.

Imaging Scans

Once abnormal hormone levels are detected, imaging techniques such as CT scans or MRIs are used to locate the tumor. If metastasis (spreading of cancer) is suspected, specialized scans like PET or MIBG (a special imaging test used to detect pheochromocytomas) may be used for a more detailed assessment.

Genetic Testing

Since some pheochromocytomas are linked to hereditary conditions, genetic testing is often recommended, particularly in younger patients, those with tumors in both adrenal glands, or those with a family history of similar conditions. Recurrence of benign tumors may also suggest an underlying genetic syndrome.

Monitoring Malignancy Risk

Patients with a history of benign pheochromocytomas require regular follow-up tests to detect the development of new tumors or signs of malignant transformation.

Treatment Modalities

Treatment modalities may depend on whether the pheochromocytoma is benign or malignant, and long-term strategies will depend on whether the patient has specific genetic mutations linked with pheochromocytoma development.

Surgical Removal

Surgery is the primary treatment for pheochromocytoma. Laparoscopic adrenalectomy is the preferred technique for removing benign tumors, which usually resolves symptoms. Patients may require medication before surgery to manage blood pressure and prevent complications.

While surgery is often curative for benign tumors, malignant pheochromocytomas may require additional treatments such as chemotherapy or radiation.

Medical Management

For patients who cannot undergo surgery or have malignant pheochromocytoma, medications can help control hormone levels and manage blood pressure.

Therapies for Malignant Pheochromocytoma 

Treatment options for cancerous pheochromocytoma may include chemotherapy, radiation, or targeted therapies like MIBG and drugs like sunitinib, which help slow tumor growth by blocking blood vessel formation.

Treatment for Familial Pheochromocytomas

Patients with a family history of pheochromocytoma need regular screenings and sometimes preventative surgeries. Genetic testing and ongoing monitoring are essential to detect the disease early and manage risks.

Health Promotion Strategies and Risk Mitigation

Factors including poor diet, sleep issues, stress, and exposure to toxins can cause or worsen hypoxia. Below are key environmental factors and lifestyle changes that can promote overall health and that may reduce the risk of hypoxia, which is a known environmental risk factor for pheochromocytoma.

Diet

A balanced diet is essential for supporting oxygenation and reducing the risk of anemia, a leading cause of hypoxia. 

Incorporating iron-rich foods like leafy greens, beans, lentils, and lean meats can prevent iron-deficiency anemia, which hinders red blood cells’ ability to carry oxygen. 

Additionally, consuming foods high in vitamin C (like citrus fruits and bell peppers) helps with iron absorption; folate and vitamin B12 (found in dark leafy greens and fortified cereals) are also necessary for red blood cell production.

Including antioxidant-rich foods such as berries, nuts, and fatty fish can also improve oxygenation by reducing inflammation and supporting healthy blood vessels; inflammation and blood vessel leakage are associated with hypoxia.

Sleep

Sleep apnea, a condition where breathing repeatedly stops during sleep, significantly lowers oxygen levels and increases the risk of hypoxia. 

Maintaining a healthy weight, using CPAP devices, and improving sleep habits may help reduce the occurrence of sleep apnea and promote better oxygen flow during rest.

Stress Reduction

Chronic stress can impair breathing patterns, elevate blood pressure, and reduce oxygen delivery to tissues. 

Practicing stress-reduction techniques such as mindfulness, meditation, deep-breathing exercises may help regulate breathing and boost overall oxygenation.

Minimizing Toxin Exposure

Exposure to environmental toxins and smoking can lead to lung damage, impaired oxygen transport, and increased risk of hypoxia. Excessive alcohol, smoking, and metabolic issues have been associated with the development of neuroendocrine tumors (NETs).

Researchers are also exploring the possibility exposure to endocrine-disrupting chemicals may be linked to NET development.

Reducing exposure to these chemicals, as well as minimizing contact with air pollution, may help lower the risk of developing conditions that contribute to hypoxia or NET development.

Genetic Counseling

For individuals with a family history of pheochromocytoma or related syndromes, genetic counseling and early screening are vital tools for risk reduction. Genetic testing can help identify at-risk individuals who may benefit from early interventions and frequent monitoring to prevent tumor development.

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Key Takeaways

• Pheochromocytoma is a rare, potentially life-threatening tumor that originates in the adrenal glands and can cause severe hypertension due to excess catecholamine production, especially norepinephrine and epinephrine.

• Both genetic mutations and environmental factors like hypoxia play significant roles in the development of pheochromocytoma, with genes such as EPAS1 and SDH being key in tumor growth.

• Hypoxia, caused by factors like congenital heart disease or high-altitude living, is strongly linked to an increased risk of pheochromocytoma, particularly through its impact on oxygen-sensing genes.