FRI323 Prolactinoma Recurrence With Testosterone Treatment In Transgender Male

Disclosure: N. Arnouk: None. P.R. Schroeder: None. Introduction: We present a case of recurrent hyperprolactinemia due to testosterone treatment for gender-affirming hormonal therapy in a transgender male after being controlled on cabergoline for more than a year. Case: A 27-year-old female with history of HTN and polycystic ovary syndrome was diagnosed with pituitary microadenoma after hospital admission for headache and blurry vision. MRI brain showed a mass in the sella and right parasella measuring 36 mm W x 36 mm D x 44 mm H. Hormonal workup showed prolactin (PRL) >999 ng/mL in the diluted assay. The patient was treated medically with cabergoline and discharged home. PRL level improved to 22 ng/mL on treatment. Cabergoline was continued at 0.5 mg twice weekly. The patient was lost to follow-up but returned to clinic after 8 months with PRL level of 58 ng/mL. Cabergoline 0.5 mg twice weekly was continued. PRL level monitoring every ∼6 weeks showed an increase to 184 ng/mL and then 199 ng/mL. Cabergoline was increased to 1 mg twice weekly. PRL level 1 month later was 222 ng/mL. Repeat brain MRI showed markedly decreased microadenoma 4.8 X 2.6 mm. The patient was asymptomatic with no headache, blurry vision, or galactorrhea. On further questioning, the patient reported starting transgender female to male testosterone cypionate 200 mg/mL once weekly for the past 6 months. After discussion with the primary care provider who was managing testosterone treatment, he was started on 60 mg weekly, and the dose was gradually increased to 80 mg weekly to stop the menstrual period. With the 60-mg weekly cypionate dose, the testosterone level was 346 pg/mL, and PRL level was 184 ng/mL. With the cypionate dose of 80 mg weekly, PRL increased to 194 ng/mL and 222 ng/mL. The cypionate dose was decreased to 60 mg weekly, based on literature noting elevated PRL level with testosterone replacement in patients with prolactinoma and hypogonadism. Based on repeat blood work showing elevated testosterone 366 pg/mL with PRL 318 ng/mL, the plan is to start an aromatase inhibitor. Discussion: Testosterone treatment as hormonal affirming therapy in some transgender female to male patients may exacerbate pre-existing hyperprolactinemia or induce PRL secretion, thus close monitoring is required. Testosterone is aromatized to estradiol, which then stimulates the release of PRL from the pituitary gland. The serial measurement of estradiol may serve as an index of aromatization. Hyperprolactinemia in this setting is resistant to dopamine agonist therapy, as noted in multiple case reports. There are no established reference ranges for PRL levels for transgender patients on gender-affirming hormone therapy and no current guidelines regarding routine imaging or biochemical assessment during follow-up. Transgender patients with prolactinoma may require additional treatment with non-aromatizable androgens or the concomitant administration of aromatase inhibitors. Presentation: Friday, June 16, 2023