A 31-year-old woman with schizophrenia started olanzapine 3 months ago and now presents with galactorrhea, amenorrhea, and weight gain. Vital signs: BP 118/76, HR 82, RR 16, Temp 37°C, SpO2 98% on room air. Serum prolactin is elevated at 65 ng/mL (normal <25). Pregnancy test is negative. TSH and free T4 are normal. Which of the following best explains her endocrine dysfunction?

1. A)Constitutive activation of the RET receptor
2. B)Blockade of dopamine inhibition of lactotrophsGABARITO
3. C)Excess ACTH production by the pituitary
4. D)Excess peripheral conversion of T4 to T3
5. E)Direct stimulation of prolactin release by thyroid hormone