By what mechanism does Risperidone swell breast tissue?

Question

There has been much talk of the anti-psychotic drug Rispeirdone causing un-natural breast tissue growth as well as galactorhea (milk production). Especially in young men and boys.What is the mechanism of this drug that is causing this? Is it actually introducing some amount of female hormones into the male's body or is just causing increased production of them?

Answer 1

Great question! There are several dopamine pathways in the brain, and the trouble with antipsychotic drugs is that they are not specific to just one of these pathways. Rather, drugs such as risperidone block dopamine receptors in all four pathways. One of these is the tuberoinfundibular pathway. Typically dopamine exerts an inhibitory affect on this pathway, suppressing the release of prolactin. When you block dopamine with risperidone, however, prolactin release is uninhibited. Prolactin is the hormone that can causes milk production, which is why galactorrhea can be an adverse effect of risperidone.