A 24-year-old man with schizophrenia treated with risperidone 4 mg daily for 1 year presents with erectile dysfunction and galactorrhea. His girlfriend also reports amenorrhea for 3 months. Physical examination reveals bilateral nipple discharge expressible on palpation. Vital signs: BP 118/76, HR 88, RR 16, Temp 37°C, SpO2 98%. Serum prolactin is 85 ng/mL (normal: 4–15 ng/mL); testosterone, TSH, and thyroid function are normal. MRI of the pituitary shows no adenoma. He denies chest pain or visual changes. Which mechanism explains this medication adverse effect?
- A)Increased thyroid-stimulating hormone from antipsychotic-induced hypothyroidism
- B)Serotonin 5-HT2A receptor antagonism promoting prolactin release
- C)Histamine H1 receptor blockade in the hypothalamus
- D)Dopamine D2 receptor blockade in the tuberoinfundibular tract relieving prolactin inhibitionGABARITO
- E)Direct stimulation of lactotroph cells in the pituitary
Explicação
Dopamine tonically inhibits prolactin release via D2 receptor activation in the hypothalamus. Antipsychotics block D2 receptors, removing this inhibition and leading to hyperprolactinemia. Risperidone is particularly potent at causing this effect due to high t... Ver explicação completa e trilha adaptativa →