Physical Traits

Males will have an increased growth velocity from early childhood to adulthood. The average final height of a male is 3 inches above the expected height. In Scotland, 8 XYY males were tested in 1967-1972, and their average height was 188.1 cm, or 6'2" at age 18, while their father's average height was 174.1 cm, or 5'8 1/2" and their mother's average height was 162.8 cm, or 5'4". There is also a chance of severe acne. Testosterone levels are also abnormally high in males with XYY Syndrome.