A 32-year-old man comes to the office due to erectile dysfunction and decreased libido for the past month. The patient has never experienced these symptoms before and finds them to be very upsetting. He has no problems with urination. The patient has a history of schizophrenia and was discharged from a psychiatric hospital 3 months ago on risperidone. He has no current delusions, and his auditory hallucinations have decreased in frequency and intensity. His thoughts are well organized. Review of systems is negative except for a recent 3-kg (6.6-lb) weight gain. Physical examination shows bilateral breast enlargement. Which of the following is the most likely mechanism responsible for this patient's decreased libido?

Question

A 32-year-old man comes to the office due to erectile dysfunction and decreased libido for the past month.  The patient has never experienced these symptoms before and finds them to be very upsetting.  He has no problems with urination.  The patient has a history of schizophrenia and was discharged from a psychiatric hospital 3 months ago on risperidone.  He has no current delusions, and his auditory hallucinations have decreased in frequency and intensity.  His thoughts are well organized.  Review of systems is negative except for a recent 3-kg (6.6-lb) weight gain.  Physical examination shows bilateral breast enlargement.  Which of the following is the most likely mechanism responsible for this patient's decreased libido?

Quizplus · Accepted Answer

11ec25c8_d757_9277_bc81_6540710d8164_MD0003_00 11ec25c8_d757_9278_bc81_c559cb7c4b68_MD0003_00 This patient has signs and symptoms of hyperprolactinemia, a condition associated with sexual dysfunction and gynecomastia in men. The tuberoinfundibular dopamine pathway projects from the hypothalamus to the pituitary gland. Normally, neurons in the tuberoinfundibular pathway secrete dopamine, which inhibits prolactin release from the anterior pituitary gland. Most antipsychotics act as dopamine antagonists, decreasing activity in this pathway by preventing dopamine from binding to D2 receptors. The second-generation antipsychotic risperidone is a serotonin-dopamine antagonist that has moderately high affinity for D2 receptors. D2 antagonism in the tuberoinfundibular pathway causes increase in prolactin levels, resulting in side effects of amenorrhea, galactorrhea, gynecomastia, and sexual dysfunction. (Choices A and D) The mesolimbic pathway extends from the ventral tegmental area to the limbic system. Decreased dopamine activity in this pathway accounts for the therapeutic effects of antipsychotics. Increased dopamine activity in the mesolimbic pathway accounts for the euphoria that accompanies drug use, as well as the delusions and hallucinations experienced in schizophrenia. (Choices B and E) The nigrostriatal pathway extends from the substantia nigra to the basal ganglia and is involved in the coordination of movement. Decreased dopamine activity in the nigrostriatal pathway causes the extrapyramidal side effects associated with antipsychotic use, as well as signs and symptoms of Parkinson disease. Increased dopamine activity in the nigrostriatal pathway is thought to be involved in some movement disorders such as chorea and tics. (Choice F) Increased dopamine activity in the tuberoinfundibular pathway inhibits rather than stimulates prolactin release. Educational objective: Antipsychotics cause hyperprolactinemia by blocking dopamine activity in the tuberoinfundibular pathway. Clinical effects of hyperprolactinemia include amenorrhea, galactorrhea, gynecomastia, and sexual dysfunction. References: Psychotropic-induced hyperprolactinemia: a clinical review. (http://www.ncbi.nlm.nih.gov/pubmed/24140188) The effects of novel and newly approved antipsychotics on serum prolactin levels: a comprehensive review. (http://www.ncbi.nlm.nih.gov/pubmed/24677189) Hyperprolactinemia and estimated dopamine D2 receptor occupancy in patients with schizophrenia: analysis of the CATIE data. (http://www.ncbi.nlm.nih.gov/pubmed/23727135)

A 32-Year-Old Man Comes to the Office Due to Erectile