What characterizes pheochromocytoma?

Pheochromocytoma is characterized by the presence of a tumor in the adrenal medulla, which is responsible for producing catecholamines such as epinephrine and norepinephrine. These hormones play a significant role in the body's fight or flight response and can lead to various systemic effects when secreted in excess. In individuals with pheochromocytoma, the overproduction of these catecholamines can lead to symptoms such as hypertension, palpitations, sweating, and anxiety.

The other options do not accurately describe pheochromocytoma. An increase in blood glucose levels is not a defining feature, although secondary stress responses can lead to elevated glucose. A tumor in the pituitary gland relates to other conditions involving pituitary function and does not pertain to pheochromocytoma directly. Meanwhile, a decrease in heart rate is contrary to what would typically be observed in this condition; catecholamine release usually leads to increased heart rate and blood pressure due to their stimulatory effects on the cardiovascular system. Thus, the defining characteristic that truly describes pheochromocytoma is the presence of a tumor that secretes catecholamines from the adrenal medulla.