Endocrine Abstracts

JOINT2422

Introduction: Prolactinomas make up nearly 50% of all pituitary tumors, with up to 20% of cases showing resistance to traditional therapy. Hormone replacement therapy (HRT) poses unique challenges in female patients with prolactinomas, as hormonal fluctuations can impact tumor behavior and treatment effectiveness. This case highlights a potential therapeutic approach for this clinical scenario.

Material and Methods: A 39-year-old female presented with complaints of pronounced fatigue, decreased libido, persistent pain in the breasts, and a weight gain of 6 kg over the past six months. The menstrual cycle was absent due to a previous hysterectomy with left ovary resection. In 2019, the prolactin (PRL) level was 50.5 ng/ml (<26.7 ng/ml). We administered cabergoline starting at 0.5 mg per week. In 2020, pituitary MRI revealed microadenoma 2.5 × 2.5 mm. Cabergoline was increased to 4.5 mg weekly, but no significant improvement was seen. In 2021, the PRL level was 1900 mU/l, also bilateral galactorrhea of Grade 2 was noted, along with pronounced breast pain and excess body weight. An MRI scan revealed an increase in pituitary adenoma size up to 3.5 mm. Bromocriptine was added, starting at 1.25 mg twice daily and increased to 2.5 mg twice daily. After a year of combined therapy, PRL decreased to 740 mIU/l, though it didn’t reach the reference range, but the patient experienced relief from breast pain. Considering the previous hysterectomy and ongoing complaints of discomfort in the breast area, tamoxifen was added to the combination therapy. In the following months, due to improved PRL levels, the cabergoline dosage was discontinued by 2022. In 2023–2024, with bromocriptine (5 mg/day) and tamoxifen (20 mg/day), PRL remained within the normal range. There were no signs of galactorrhea or breast pain, and a 10 kg weight loss was noted. Due to complaints of low mood and menopausal hot flashes, the patient was offered HRT with tibolone 2.5 mg daily with discontinuation of tamoxifen. After one month, she reported improved mood, sleep, and relief from symptoms that had troubled her for 5 years, with the PRL level also within the reference range.

Results: Tibolone, unlike traditional HRT, selectively activates estrogen receptors, minimizing prolactin secretion and tumor risk. This makes it a safer option for menopausal women with well-controlled prolactinomas.

Conclusions: HRT helps manage vasomotor symptoms and prevent osteoporosis, but estrogen can stimulate tumor growth. Tibolone’s dual action—antiestrogenic on breasts, estrogenic on the hypothalamus—suggests its potential use in menopausal prolactinoma patients.