HTR2C (serotonin 2C receptor) is a subtype of the serotonin or HTR2 receptor. HTR2C receptors are distributed throughout the brain, notably in areas associated with executive function, memory, emotional processing, feeding behavior, and motor function. Agonism of the receptor is associated with decreased food consumption, and antagonism is associated with increased food consumption. Atypical antipsychotics, such as olanzapine (Zyprexa®) and risperidone (Risperdal®), bind tightly to HTR2C receptors, and polymorphisms in this gene may affect the activity and density of these serotonin receptors. Polymorphisms in the HTR2C receptor have been linked to antipsychotic-induced weight gain.  Genetic variant tested for HTR2C is c.-759C>T.
Indication for HTR2C Testing
Individuals initiating therapy with an antipsychotic may consider HTR2C testing. Testing for HTR2C may predict which patients are more likely to experience antipsychotic-induced weight gain. Assessment of medical necessity for testing is up to the provider’s clinical judgment. The majority of research on HTR2C polymorphisms’ relation to antipsychotic response has been conducted in schizophrenia patients.