Pheochromocytoma and Weight Loss

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Pheochromocytoma is a tumour that produces cat-echolamines and is usually derived from adrenomedullary chromaffin cells. When it arises from extra-adrenal chromaffin cells, the tumours are called extra-adrenal PCC or paragangliomas. Similar clinical manifestations may occur in other related tumours that secrete catecholamines, such as chemodectomas and ganglioneuromas [26, 31]. The rarity of PCCs (fewer than 1% of hypertensive patients) should not reduce the importance of these tumours. In fact, when diagnosed and treated, PCC is curable, while when misdiagnosed it can be fatal. Most PCC (90%) are benign. Occasionally PH is inherited as an autosomal dominant trait and may be part of a multiple endocrine neoplasia (MEN) syndrome. PCCs occur at any age, but the incidence increases throughout life, in women more than in men [31,32].

The clinical manifestations of PCC are due to the effects of the catecholamines that are stored and released in an uncontrolled way and in large amounts by the tumours [32, 33]. They include: (1) sustained hypertension resistant to conventional treatment, (2) hypertensive crisis with malignant hypertension, (3) paroxysmal attacks suggestive of seizure disorders, anxiety attacks, or hyperventilation. Less common manifestations are orthostatic hypotension and shock, cardiac manifestations (ischaemic manifestations or cardiomyopathy), and metabolic manifestations, including weight loss.

Weight loss in PCC patients is usual, although obesity cannot exclude the diagnosis. The weight reduction is partly due to increased metabolic rate, excessive sweating, and heat intolerance. Fever may also be present [31-33]. Weight loss is sustained by an activation of lipolysis in white adipose tissue. An activation of brown fat is also evident in patients with PCC [34]. It is noteworthy that, while adipose tissue constitutes the bulk of body fat stores and primarily has as an energy storage function, brown adipose tissue functions principally to generate heat in humans and many other species [34].

Gastrointestinal symptoms can also contribute to weight loss. They include nausea, vomiting, abdominal pain, and, occasionally, constipation or diarrhoea. Constipation may reflect direct inhibitory effects of catecholamines on gut smooth-muscle contraction. The so-called watery diarrhoea, hypokalaemia, achlorydria syndrome ([WDHA], also known as Verner-Morrison syndrome) in patients with PCC is secondary to the ectopic production of vasoactive intestinal polypeptide (VIP) [35]. These symptoms, including weight loss, resolve after the tumour is removed [26,35].

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