Hormonal Syndromes Caused by Lung Neuroendocrine Tumors

Lung neuroendocrine tumors (NETs) can cause diverse symptoms and complications based on the hormones they produce. A ‘functional’ NET is a tumor producing a substantial amount of hormone-like substances called neuropeptides. Each type of neuropeptide produced by lung NETs regulates different bodily functions. The excess neuropeptides can cause a range of symptoms simultaneously (syndrome).

Here are the hormonal syndromes linked to lung NETs.

Carcinoid syndrome arises when neuroendocrine tumors release significant quantities of serotonin into the bloodstream. While rare in lung NETs, it is still possible if the tumor attains a considerable size. Notably, lung NETs produce smaller amounts of serotonin compared to gastrointestinal NETs. Symptoms include:

• Flushing of face and neck
• A drop in blood pressure (hypotension)
• Fast heart rate (tachycardia)
• Diarrhea, stomach cramps and loss of appetite
• Wheezing – difficulty breathing
• Spider veins – visible purple veins on the lips and nose

Cushing’s syndrome occurs in approximately 1-2% of lung NETs. The medical condition results from an excessive amount of cortisol hormone in the body. In the case of lung NETs, the tumor releases adrenocorticotropic hormone (ACTH). This ectopic source, along with the normal ACTH produced pituitary and adrenal glands, induce an overproduction of cortisol. Symptoms arise from cortisol overproduction include:

• a rounder face
• increased weight around the middle body and upper back, arms and legs remain thin
• high blood sugar (hyperglycemia) or diabetes
• high blood pressure (hypertension)
• lethargic or emotional
• brittle bones (osteoporosis)

The onset of Cushing’s syndrome is usually acute, triggering the need for medical attention. Often, patients discover their lung NETs when they see a doctor for Cushing’s syndrome.

Acromegaly is a rare disorder characterized by excessive growth hormone, causing abnormal growth of body parts during adulthood. Lung NETs are the most common cause of out-of-place growth-hormone-releasing hormone (GHRH) production.