Veterinary Physiology-III

SYNERGISM AND ANTAGONISM

• The activity of one hormone may be influenced by its interaction with one or more hormones involved in the regulation of the same function.
• The actions of different hormones are concerted or additive if they produce the same response and the combined effect of the hormones is the sum of separate actions of the individual hormones. In this case, the two hormones act by different mechanisms.
• In some cases, two hormones can produce the same effect but the effects due to the different hormones are non-additive, i.e. the two hormones act by the same common mechanism.
• Some hormones may act together to produce greater total effect than their individual effects known as synergistic effect. E.g., the toxicity of catecholamines is increased by thyroxine.
• Some hormones exhibit opposite effects of other hormones known as the antagonism; e.g., Insulin and glucagon actions on blood glucose level.
• When one hormone is required for another hormone to exert its effect it is called permissive effect; e.g., small amount of glucocorticoids is needed for catecholamines to produce their calorigenic and lipolytic effects.