is abnormally large growth due to an excess of growth hormone (GH) during childhood, before the bone growth plates have closed (epiphyseal fusion). It causes excessive growth in height, muscles, and organs, making the child extremely large for age. Other symptoms may include delayed puberty; double vision or difficulty with side (peripheral) vision; prominent forehead (frontal bossing) and a prominent jaw; headache; increased sweating (hyperhidrosis); irregular periods; large hands and feet with thick fingers and toes; thickening of the facial features; and weakness. It may begin at any age before epiphyseal fusion. The most common cause is a non-cancerous (benign) tumor of the pituitary gland, which may cause it to make too much GH, but it can be caused by other underlying conditions (which may cause a pituitary tumor) including Carney complex; McCune-Albright syndrome (MAS); Multiple endocrine neoplasia type 1 (MEN-1); and Neurofibromatosis. Treatment typically includes surgery to remove the tumor and can cure many cases. Medication or radiation therapy may be used to reduce GH release or block the effect of GH. If the condition occurs after normal bone growth has stopped (in adulthood), it is referred to as acromegaly. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.