**Question:** Which one of the following clinical features is NOT seen in Phaeochromocytoma?

A. Hypertension
B. Palpitation
C. Diabetes mellitus
D. Obesity

**Core Concept:**
Phaeochromocytoma is a rare, benign tumor that arises from chromaffin cells in the adrenal medulla or sympathetic ganglia. These tumors secrete excessive amounts of catecholamines, such as epinephrine and norepinephrine, leading to characteristic clinical features.

**Why the Correct Answer is Right:**
Phaeochromocytomas are known to cause hypertension and palpitation due to the excessive release of catecholamines. Diabetes mellitus is typically associated with insulin resistance, which is usually caused by conditions like obesity, diabetes, or medications rather than a tumor. Obesity is often linked to hypertension and diabetes, but it is not directly caused by a Phaeochromocytoma.

**Why Each Wrong Option is Incorrect:**
Hypertension and palpitation are common symptoms of Phaeochromocytoma due to excessive catecholamine secretion. Diabetes mellitus is not a direct feature of Phaeochromocytoma but can be associated with obesity, which is often seen in patients with hypertension and diabetes.

**Clinical Pearl:**
Phaeochromocytomas should be considered in the differential diagnosis of patients presenting with hypertension, palpitation, and/or paroxysmal sweating. In the context of obesity, hypertension, and diabetes, clinicians should explore other potential causes like obesity itself, diabetes medications, or other endocrine disorders before attributing these symptoms solely to a Phaeochromocytoma. This is crucial to ensure proper diagnosis and treatment for the patient.

**Correct Answer:**
D. Obesity

**Explanation:** Obesity is a common feature in patients with hypertension and diabetes but is not directly caused by a Phaeochromocytoma. Obesity is often associated with lifestyle factors, other endocrine disorders, or medications, and should be ruled out before concluding that a patient's symptoms are solely due to a Phaeochromocytoma.