Which symptom is most characteristic of a pituitary adenoma?

Which symptom is most characteristic of a pituitary adenoma?

• A. Bitemporal vision loss
• B. Monocular vision loss
• C. Hyperpigmentation
• D. Seizures

Answer: (A)

Compression of the optic chiasm by a pituitary adenoma is the classic cause of this symptom. The fibers carrying the nasal (inner) visual field from each eye cross at the chiasm, so a tumor growing upward from the sella presses on these crossing fibers and produces loss of peripheral vision in both eyes—bitemporal (or tunnel) vision. Central vision often remains intact early on and is affected only when the tumor enlarges further. The other options don’t fit this pattern: monocular vision loss suggests disease before the chiasm (optic nerve or retina), hyperpigmentation is not a typical early sign of a pituitary adenoma, and seizures are not characteristic of this condition.

Compression of the optic chiasm by a pituitary adenoma is the classic cause of this symptom. The fibers carrying the nasal (inner) visual field from each eye cross at the chiasm, so a tumor growing upward from the sella presses on these crossing fibers and produces loss of peripheral vision in both eyes—bitemporal (or tunnel) vision. Central vision often remains intact early on and is affected only when the tumor enlarges further. The other options don’t fit this pattern: monocular vision loss suggests disease before the chiasm (optic nerve or retina), hyperpigmentation is not a typical early sign of a pituitary adenoma, and seizures are not characteristic of this condition.