Complex sentence: Stadnyk's excessive growth began after brain surgery when he was 14 years old after which he developed a pituitary gland tumor which caused the gland to secrete large amounts of growth hormone, resulting in what doctors describe as acromegalic gigantism.
Split into simpler sentences: Stadnyk's excessive growth began after brain surgery when he was 14 years old. He developed a pituitary gland tumor which caused the gland to secrete large amounts of growth hormone, resulting in what doctors describe as acromegalic gigantism.