A 32-year-old woman presents with amenorrhea, galactorrhea, and visual field defects, all of several months duration. Magnetic resonance imaging reveals a hypophyseal mass impinging on the optic chiasm. This is most likely
**Core Concept**
The patient's presentation of amenorrhea, galactorrhea, and visual field defects, along with a hypophyseal mass on MRI, suggests a pituitary tumor causing hormonal and visual disturbances. This is a classic case of a prolactinoma, a type of pituitary adenoma that secretes excess prolactin, leading to lactation and hormonal imbalances.
**Why the Correct Answer is Right**
Prolactinomas arise from lactotroph cells in the anterior pituitary gland and secrete excess prolactin, which stimulates milk production and disrupts normal menstrual cycles. The tumor's location and growth pattern impinge on the optic chiasm, causing visual field defects due to compression of the optic nerves. The patient's symptoms, including amenorrhea and galactorrhea, are direct consequences of hyperprolactinemia.
**Option A:** This option is incorrect because a thyroid-stimulating hormone (TSH) secreting tumor would not typically cause amenorrhea, galactorrhea, or visual field defects. TSH-secreting tumors primarily lead to hyperthyroidism symptoms.
**Option B:** This option is incorrect because a growth hormone (GH) secreting tumor would primarily cause acromegaly symptoms, such as excessive growth of hands and feet, rather than amenorrhea, galactorrhea, or visual field defects.
**Option C:** This option is incorrect because a non-functioning pituitary adenoma would not secrete excess hormones and would not typically cause the patient's symptoms. These tumors are often discovered incidentally and may cause visual field defects due to compression, but they do not secrete excess hormones.
**Option D:** This option is incorrect because a craniopharyngioma is a type of brain tumor that arises near the pituitary gland, but it is not typically associated with the patient's symptoms of amenorrhea, galactorrhea, and visual field defects.
**Clinical Pearl / High-Yield Fact**
The "rule of 10s" for pituitary tumors states that 10% of functioning pituitary adenomas are prolactinomas, 10% are non-functioning adenomas, and 10% are malignant; the remaining 70% are other types of functioning adenomas.
**Correct Answer:** C. Non-functioning pituitary adenoma.