Gigantism and dwarfism. Historical image of two men suffering from growth disorders. The man at right suffers from gigantism. He is seen with an adult man who suffers from dwarfism. Gigantism is caused by a childhood tumour of the pituitary gland, the organ which produces growth hormone. The gland becomes overactive, leading to an increased growth rate and muscular weakness. Sufferers usually die in early adulthood when the tumour finally destroys the gland. Dwarfism has a variety of causes, including a deficiency of growth hormone or a lack of the metabolism- controlling hormone produced by the thyroid gland.