Hyperprolactinemia is potentially associated with amenorrhoea, galactorrhoea, sexual dysfunction,44 breast engorgement, and osteoporosis.37,45 Neuroscientists began investigations into prolactin levels as an indicator of hypothalamic activity during psychiatric illness19 and following the observation in animals that many antipsychotics stimulate prolactin secretion46,47 consistent with prolactin levels being an indicator of dopamine blockade and generating the hypothesis that increased serum prolactin levels were associated with antipsychotic clinical efficacy. The gene discussed is PRL; the disease is sexual dysfunction.