8231 Hyperprolactinemia Post-Brain Radiation

Disclosure: R. Kalas: None. V. Manohar: None. N.S. Bapat: None. Y. Kim: None. Hormonal dysfunction in adults is common after brain radiotherapy, especially when the hypothalamus or the pituitary gland is within the field of radiation. Following cranial radiotherapy, it is crucial to routinely monitor the emergence of hormonal imbalances, with particular attention to the somatotroph-GH axis, which is most frequently affected. Notably, hyperprolactinemia may manifest in 5%-50% of individuals following radiation. The degree and extent of the hormonal disorder can depend on radiation dose and technique, and the length of time after radiation. We report a case of hyperprolactinemia occurring five years after radiotherapy for cavernous sinus schwannoma. A 44-year-old woman with a history of cavernous sinus schwannoma status post right pterional craniotomy and radiation therapy 5 years prior presented with a 4-month-history of secondary amenorrhea. She underwent pencil beam scanning proton radiation to the right orbital apex and cavernous sinus for a dose of 5040 cGy in 28 fractions. Review of systems was negative for hot flashes, breast tenderness, or galactorrhea. Labs revealed: diluted prolactin 118 (4.8-23.3 ng/mL), monomeric prolactin 99.6 (4.79-23.3 ng/ml), estradiol 184 pg/ml, LH 10.5 mIU/mL, FSH 2.9 mIU/mL, serum beta-HCG <5 mIU/mL, TSH 2.630 (0.450-4.500 mIU/L), free T4 0.85 (0.82-1.77 ng/dL), IGF-1 104 ( 74-239 ng/mL), and ACTH 17.8 (7.2-63.3 pg/mL) with morning cortisol 14.0 (6.2-19.4 ug/dL). A brain MRI with and without contrast revealed stable mass with postsurgical changes in the right cavernous sinus extending to the orbital apex and no abnormalities of the pituitary gland when compared to 2 years ago. The patient was started on cabergoline 0.5 mg twice a week. Her menses resumed four weeks after starting treatment, and the prolactin level repeated one month after was <1.0 ng/mL. The proposed mechanism for radiation-induced hyperprolactinemia is damage to the hypothalamus resulting in reduction of dopamine, an inhibitory neurotransmitter. It is typically dose dependent, and for the majority, it is subclinical occurring years after radiation. It can develop in both sexes and all ages but most commonly amongst young women. Hyperprolactinemia can sometime self-resolve, potentially due to evolving damages to lactotrophs. We emphasize that while brain radiotherapy can frequently lead to hormonal deficiencies, hyperprolactinemia can occur and eventually lead to dysfunction in the LH/FSH axis. Pituitary function should be routinely checked for many years post-radiation, as the likelihood of developing hormonal dysfunction tends to increase with time. Presentation: 6/1/2024