Hormones are chemicals that send signals from one cell to another via the blood, regulating the function of their target. Endocrine hormone molecules are secreted (released) directly into the bloodstream, while exocrine hormones (or ectohormones) are secreted directly into a duct, and from the duct they either flow into the bloodstream or they flow from cell to cell.

Hormones fall into three categories:

• Amine-derived hormones are derivatives of the amino acids tyrosine and tryptophan. Examples are catecholamines and thyroxine.
  
• Peptide hormones consist of chains of amino acids
  small peptide hormones include TRH/TRF (thyroid stimulating hormones) and vasopressin (regulates the body’s water retention)
  proteins are made up of hundreds of amino acids, such as insulin and growth hormone
  
• glycoprotein hormones link carbohydrates (sugar) to proteins

Lipids are fats (subgroup of triglycerides – not fatty acids), oils, waxes, cholesterol, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, etc.

Lipids:

• assist in the storage of energy and metabolism
  
• regulate calcium mobilization, cell growth, inflammation and immunity, as well as steroid hormones (which modulate functions such as reproduction, metabolism and blood pressure)