(b) : Hormones are chemical messengers produced by the ductless glands (sometimes by neurons) and transported in the circulation to target cells. They regulate metabolic processes. Chemically hormones are of different nature like biogenic amines (like thyroxine, adrenaline etc), proteinaceous or polypeptide (like hypothalamic hormones etc.) and steroids (like sex hormones and adrenocorticoids).