May 1936, Robert Wadlow at 18 years old with his mother and brother Harold Jr.  is the tallest person in medical history for whom there is irrefutable evidence.  Robert Wadlow reached 8 feet 11.1 inches (272 cm) in height and weighed 490 pounds (220 kg) at his death. His great size and his continued growth in adulthood was due to hypertrophy of his pituitary gland which results in an abnormally high level of human growth hormone.