P-53 Resistant macroprolactinoma

Abstract Introduction Dopamine agonists (DAs) are considered to be the mainstay treatment for prolactinomas. Primary DA-resistance has been reported in approximately 20–30% of the patients on bromocriptine, and in around 10% of those on cabergoline. The DA-resistance is usually defined as a failure to achieve normal prolactin levels on maximally tolerated doses of DAs for at least 3-6 months and failure to achieve 30-50% reduction in tumor size in case of macroprolactinoma. Most of resistant prolactinomas have shown to be large and/or invasive tumors. We present a clinical case of microprolactinoma, resistant to cabergoline. Clinical Case A 21-year old woman reported of a 2-year history of amenorrhea. Primary examination revealed hyperprolactinemia up to 361 ng/ml (bioactive prolactin 256 ng/ml). MR imaging with contrast enhancement showed the ovoid microadenoma in the right half of the adenohypophysis up to 10 mm without invasion to cavernous sinus (Figure 1). Hormone tests excluded the overproduction of ACTH, GH and TSH by the tumor (Table 1), and revealed no signs of hypopituitarism. The patient was prescribed cabergoline (0.5 mg per week), which was followed by the initial decrease of prolactin level to 116 ng/ml. However, subsequent increase of cabergoline dose up to 4,5 mg per week did not lead to further prolactin decrease and normoprolactinemia and there was no resumption of menstrual function. On the follow-up MR images (6 months after the first one) no dynamics was revealed: the tumor was up to 10 mm in size without invasive spreading to cavernous sinus or chiasm. Taking into account the resistance to cabergoline, young age and pregnancy planning, the patient underwent transnasal debulking of the tumor. A week after the operation, normalization of prolactin level was noted, and there were no any signs of hypopituitarism. Within a month after operation, the patient reported of resumption of regular menstrual cycle. r4 months later the woman got pregnant. The pregnancy proceeded without complications and ended in timely delivery.Figure 1.MR image of pituitary microadenoma (contrast enhanced)  Table 1.Primary hormone examination