Anabolism is the aspect of metabolism that is characterized by growth. One way of categorizing metabolic processes, whether at the cellular, organ or organism level is as anabolic or catabolic.

Anabolic processes tend toward "building up" organs and tissues. These processes produce growth and differentiation of cells and increase in body size, a process that involves synthesis of complex molecules. Examples of anabolic processes include growth and mineralization of bone and increase of muscle mass.

Catabolic processes involve "breaking down" organs and tissues. These processes involve "dismantling" of structural proteins for recycling for other purposes. Catabolic processes occur during starvation, stress and illness. Examples of catabolic processes include breakdown of muscle protein in order to use amino acids as substrates for gluconeogenesis (much like burning furniture in your house as fuel because you are out of firewood), and breakdown of fat in adipose to fatty acids for fuel.

Because it is counterproductive to have anabolic and catabolic processes occurring in cells simultaneously, there are many signals that switch on anabolic processes while switching off catabolic processes and vice versa. Most of the known signals are hormones of various types. Endocrinologists have traditionally classified many of the hormones as anabolic or catabolic.

• Classic anabolic hormones include
  • Growth hormone
  • IGF1 and other insulin-like growth factors
  • Insulin
  • Testosterone
  • Estrogen
• Classic catabolic hormones include
  • Cortisol
  • Glucagon
  • Adrenalin and other catecholamines
  • Cytokines
• Newer hormones associated with the balance of the catabolic and anabolic states include
  • Orexin and Hypocretin (a hormone pair)
  • Melatonin

See also

Anabolic steroids