Symptoms of Carcinoid Syndrome

If you’ve been diagnosed with a neuroendocrine tumor, you might have heard of carcinoid syndrome. Carcinoid syndrome is characterized by a wide range of symptoms, some of which may be challenging to deal with. Learning more about these symptoms and understanding how they come about can help you manage and cope with them better. By staying informed, you can navigate your treatment journey with confidence and preparedness.

Carcinoid tumors are a subset of neuroendocrine tumors, and can arise in the gastrointestinal tract or the lungs. These tumors release abnormally high levels of bioactive substances, like hormones, into your bloodstream. When these substances are not broken down and allowed to circulate throughout your body, it may cause a wide range of symptoms collectively known as carcinoid syndrome.

Carcinoid tumors typically release high levels of serotonin. As such, carcinoid syndrome can be diagnosed with the 24-hour urine test for 5-hydroxyindoleacetic acid (5-HIAA), which measures the byproduct of serotonin breakdown.

In the long-term, the main concern for carcinoid syndrome would be the risk of damage to the heart valves (e.g. right-side valvular failure), which can cause difficulties in breathing or weakness. Consequently, those with carcinoid syndrome would need a routine transthoracic echocardiogram (TTE) to check for this.

Diarrhea

Diarrhea refers to the frequent occurrence of loose and watery stools. It is sometimes accompanied by abdominal cramps in carcinoid syndrome.

If left untreated, diarrhea can become so severe that your body is depleted of vital nutrients, such as potassium and water. This can potentially lead to life-threatening complications like electrolyte imbalance and dehydration. Suffering from diarrhea can also result in the malabsorption of nutrients within your small intestine.

Diarrhea in carcinoid syndrome is mainly mediated by serotonin, which is known to stimulate gut motility and secretion. Other bioactive substances, like tachykinins and kallikrein, can also cause diarrhea to some extent if produced at abnormally high levels.

Flushing

One of the most distinctive symptoms of carcinoid syndrome is flushing. This is the sensation of warmth and the development of red, pink or purple areas on your skin. It is largely caused by widening or dilation of the blood vessels. Flushing can happen at the same time as a fall in blood pressure (hypotension) and increased heart rate (tachycardia).

The bioactive substance likely responsible for causing flushing is histamine. For this reason, flushing (with pruritus) is the primary manifestation or hallmark of carcinoid syndrome.

Telangiectasia

Telangiectasia refers to the appearance of thread-like, tiny blood vessels close to the surface of the skin on your face. These blood vessels appear as fine pink, red or purple lines, usually on your nose and upper lip. Telangiectasia is a consequence of recurrent severe flushing episodes and can become semi-permanent over time. They are commonly known as "spider veins".

Wheezing

Wheezing is the shrill, high-pitched, whistling sounds that occur while you are breathing. It is frequently associated with shortness of breath and may happen concurrently with flushing. Wheezing is caused by the tightening of the airways, also known as bronchoconstriction or bronchospasm. While the underlying mechanism behind this symptom remains unclear, it is most likely linked to the release of histamine.

Edema

If you suffer from severe flushing attacks, you may experience an advanced manifestation of carcinoid syndrome known as brawny edema. When this happens, your face and sometimes your extremities (feet and legs) become hard and swollen because of excess fluid in your body tissues.

Lacrimation

Lacrimation refers to the excessive and abnormal production of tears that is normally caused by eye irritation or injury.