Partial Agonist

[usmlesuccess]

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Just to clear things up, is a partial agonist when a hormone has mixed agonist/antagonist properties, which does not produce the full affect of the hormone, like clomiphene?

 

[Phloston]

Just to clear things up, is a partial agonist when a hormone has mixed agonist/antagonist properties, which does not produce the full affect of the hormone, like clomiphene?

As far as I'm aware, a partial-agonist is just an agent that induces a positive effect (i.e. it actually has true agonist function), however it results in decreased Vmax. The Km can be higher or lower.

Clomiphene, as you've said, is a good one. If the resultant Vmax is substantially lesser, the agent can appear to have antagonist effects, but there's actually nothing antagonistic occurring because a degree of positive reaction rate persists.

One similar term I had picked up somewhere is physiologic agonist, which is an agent that antagonizes the effects of another agonist by producing the opposite, agonistic effects (e.g. glutamate, with respect to GABA). They must also bind at different sites.

 

[usmlesuccess]

Thanks phloston for the explanation!