Gigantism and dwarfism. Composite image of three people, two suffering from growth disorders. The men suffer from gigantism (at centre) and dwarfism (at upper left) whilst the woman is of normal height. Gigantism is caused by a tumour in the pituitary gland, the organ which produces growth hormone, during childhood. This makes the gland overactive, leading to an increased growth rate and muscular weakness. Sufferers usually die in early adulthood when the tumour finally destroys the gland. Dwarfism is caused by hereditary disorders, a deficiency of growth hormone or a lack of metabolism-controlling thyroid hormone.