The "5 H's" of pheochromocytoma are a mnemonic used to remember the most common signs and symptoms associated with this rare, hormone-secreting tumor of the adrenal glands. It's important to note that not all patients with pheochromocytoma will experience all five.
Here's a breakdown of each "H":
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Hypertension: High blood pressure, which can be persistent or occur in sudden episodes (paroxysms). This is due to the excess release of catecholamines (epinephrine and norepinephrine) by the tumor.
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Headache: Often severe and throbbing, caused by the surge in blood pressure.
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Hyperhidrosis: Excessive sweating, also driven by the increased catecholamine levels.
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Hypermetabolism: Increased metabolic rate leading to weight loss, heat intolerance, and tremors. The increased catecholamines stimulate metabolism.
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Hyperglycemia: Elevated blood sugar levels. Catecholamines inhibit insulin secretion and promote glycogenolysis and gluconeogenesis (breakdown of glycogen and production of glucose, respectively), resulting in increased blood glucose.
While these are the classic "5 H's," it's crucial to remember that they are not always present. A significant portion of patients (around 30%) may not exhibit all of these symptoms. Therefore, a high index of suspicion is required for diagnosis, and biochemical testing (measuring catecholamine levels) is essential.
