(a) X is the pituitary gland. It is located just below the brain.
(b) The chemical substance (Y) released from the pituitary gland is human growth hormone.
(c) Under-secretion of growth hormone leads to a condition known as dwarfism. In dwarfism, the person remains very short.
(d) Over-secretion of growth hormone causes a condition known as gigantism. In gigantism, the person grows very tall.
(e) The pituitary gland (X) is a part of the endocrine system.