What symptom is typically associated with elevated prolactin levels?

Elevated prolactin levels are most commonly associated with galactorrhea, which is the unexpected production of breast milk not associated with normal breastfeeding. Prolactin is a hormone primarily responsible for regulating milk production in mammals. When prolactin levels are elevated due to various factors, including pituitary tumors (such as prolactinomas), certain medications, or other health conditions, individuals may experience galactorrhea even if they are not pregnant or breastfeeding.

While symptoms like weight gain can sometimes be seen in patients with excessive prolactin levels, they are not as directly linked to the hormone's primary function compared to galactorrhea. Excessive thirst and hyperactivity also do not correlate with high prolactin levels and are associated with other hormonal imbalances or medical conditions. Thus, galactorrhea stands out as the key symptom connected with elevated prolactin, making it the correct answer.