Which biological mechanism explains why some antipsychotic medications can cause gynecomastia in adolescent males?

Which biological mechanism explains why some antipsychotic medications can cause gynecomastia in adolescent males?

• A. Blockade of dopamine in the tuberoinfundibular pathway leading to increased prolactin
• B. Blockade of acetylcholine causing gynecomastia
• C. Increased serotonin causing breast tissue growth
• D. Antagonism at NMDA receptors causing gynecomastia

Answer: (A)

Dopamine normally keeps prolactin levels in check through D2 receptors on lactotroph cells in the anterior pituitary, a pathway known as the tuberoinfundibular pathway. When an antipsychotic blocks these D2 receptors, this inhibitory brake is released, leading to increased prolactin in the blood (hyperprolactinemia). Elevated prolactin stimulates breast tissue growth, which can manifest as gynecomastia in adolescent males. This direct link between D2 blockade and higher prolactin explains why many antipsychotics cause gynecomastia. The other options don’t fit as the primary mechanism: acetylcholine blockade isn’t known to cause gynecomastia, serotonin’s effect on prolactin is indirect and not the main driver in this context, and NMDA receptor antagonism isn’t how these drugs induce breast tissue growth.

Dopamine normally keeps prolactin levels in check through D2 receptors on lactotroph cells in the anterior pituitary, a pathway known as the tuberoinfundibular pathway. When an antipsychotic blocks these D2 receptors, this inhibitory brake is released, leading to increased prolactin in the blood (hyperprolactinemia). Elevated prolactin stimulates breast tissue growth, which can manifest as gynecomastia in adolescent males. This direct link between D2 blockade and higher prolactin explains why many antipsychotics cause gynecomastia. The other options don’t fit as the primary mechanism: acetylcholine blockade isn’t known to cause gynecomastia, serotonin’s effect on prolactin is indirect and not the main driver in this context, and NMDA receptor antagonism isn’t how these drugs induce breast tissue growth.