From the Guidelines
5-HIAA (5-hydroxyindoleacetic acid) is a crucial biomarker for diagnosing and monitoring carcinoid syndrome, and its levels should be interpreted with caution, considering dietary and medication interference, as evidenced by the most recent study 1. When evaluating 5-HIAA levels, it is essential to consider the patient's diet and medication use, as certain foods and drugs can affect test results. Patients should avoid consuming avocados, bananas, cantaloupe, eggplant, pineapples, plums, tomatoes, hickory nuts, plantains, kiwi, dates, grapefruit, honeydew, or walnuts for 48 hours before the start of urine collection, as well as coffee, alcohol, and smoking during this period 1. Additionally, medications such as acetaminophen, ephedrine, diazepam, nicotine, guaifenesin, and phenobarbital can increase 5-HIAA levels and should be disclosed to healthcare providers. The test works by measuring the main metabolite of serotonin in urine or cerebrospinal fluid, which helps diagnose conditions like carcinoid syndrome, a rare disorder caused by carcinoid tumors that secrete excessive serotonin. Normal urine 5-HIAA levels typically range from 2-8 mg per 24 hours, with elevated levels potentially indicating carcinoid tumors or other serotonin-producing neoplasms. Some key points to consider when interpreting 5-HIAA levels include:
- Decreasing levels of 5-HIAA indicate a response to treatment, whereas increasing or excessive concentration indicates that the treatment has not been successful 1.
- A patient with symptoms may still have a carcinoid tumor even if the concentration of 5-HIAA is normal 1.
- Somatostatin receptor scintigraphy is not routinely recommended for surveillance after definitive resection but may be indicated to assess disease location and disease burden for comparison in cases of subsequent possible recurrence 1. Overall, 5-HIAA is a valuable biomarker for diagnosing and monitoring carcinoid syndrome, and its levels should be interpreted with caution, considering dietary and medication interference, to ensure accurate diagnosis and effective treatment.
From the Research
Definition and Role of 5-HIAA
- 5-HIAA, or 5-hydroxyindoleacetic acid, is a compound that plays a significant role in the diagnosis and management of carcinoid syndrome 2, 3, 4, 5, 6.
- It is a metabolite of serotonin, a hormone produced by neuroendocrine tumors that can cause carcinoid syndrome 2, 3, 4, 5, 6.
Measurement and Significance of 5-HIAA
- Urinary 5-HIAA is often measured to assess the severity of carcinoid syndrome and to monitor the effectiveness of treatment 2, 3, 4, 5, 6.
- Elevated levels of 5-HIAA in the urine are associated with increased serotonin production, which can contribute to the symptoms of carcinoid syndrome, such as diarrhea and flushing 2, 3, 4, 5, 6.
Treatment Implications
- Reducing 5-HIAA levels through treatment can lead to improved symptoms and quality of life for patients with carcinoid syndrome 2, 3, 4, 5, 6.
- Various treatments, including somatostatin analogues, serotonin synthesis inhibitors, and interferon, have been shown to decrease 5-HIAA levels and alleviate symptoms of carcinoid syndrome 2, 3, 4, 5, 6.