What symptom is commonly associated with gigantism?

Gigantism is a condition that results from excessive growth hormone levels, typically due to a pituitary adenoma. One of the hallmark symptoms of gigantism is abnormally tall stature, which occurs because the excess growth hormone stimulates growth plates in bones, leading to increased height. This condition is characterized by tallness specifically in children and adolescents before the growth plates close, allowing for continued growth in height.

While the other symptoms listed, such as lengthened maxilla, enlarged extremities, and deepened voice, can be associated with acromegaly (which occurs in adults after the growth plates have closed), the primary and defining symptom of gigantism is the noticeable increase in height during the growth period of a person's life. Thus, abnormally tall stature is the correct answer, as it directly captures the essence of what gigantism entails.