**Core Concept**
Galactorrhea refers to the spontaneous flow of milk from the breast not associated with childbirth or nursing. It is often a symptom of prolactinoma, a type of pituitary adenoma that secretes excess prolactin. This condition can be caused by various factors, including hormonal imbalances, medications, and certain medical conditions.

**Why the Correct Answer is Right**
The correct answer is related to the pathophysiology of galactorrhea. Galactorrhea is typically caused by an excess of prolactin, which stimulates milk production in the breasts. Prolactin is secreted by the pituitary gland, and an overproduction of prolactin can be caused by conditions such as prolactinoma, hypothyroidism, or certain medications like dopamine antagonists.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because galactorrhea is not typically associated with an increase in gonadotropin-releasing hormone (GnRH). GnRH is involved in the regulation of the reproductive axis, but it is not directly related to prolactin secretion.
**Option B:** This option is incorrect because galactorrhea can be caused by a variety of factors, including hormonal imbalances, medications, and certain medical conditions, but it is not exclusively caused by a pituitary adenoma.
**Option C:** This option is incorrect because galactorrhea is not typically associated with an increase in thyroid-stimulating hormone (TSH). While hypothyroidism can cause an increase in prolactin, it is not the primary cause of galactorrhea.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that galactorrhea can be a symptom of an underlying medical condition, such as a prolactinoma or hypothyroidism. Therefore, it is essential to investigate the underlying cause of galactorrhea to provide appropriate treatment.

**Correct Answer: B. Galactorrhea is not exclusively caused by a pituitary adenoma.**