Endocrine Abstracts

Introduction: Prolactinoma is the most frequent secreting pituitary tumor. They are usually treated with dopamine agonists (DA) (bromocriptine and cabergoline), which are very effective in most cases. DA resistance consists of the impossibility of reaching normal prolactin levels and/or reduction of the adenoma by at least 50%.

Case presentation: We present the case of a 57-year-old man affected by visual disturbances and hypopituitarism (2019). Pituitary MRI showed a 25×30×27mm pituitary cystic macroadenoma with displacement of the pituitary stalk, suprasellar extension displacing and compressing the optic chiasm (superior temporal quadrantanopia) and lateral expansion towards the cavernous sinuses. The prolactin level was very high (345 mg/dl [3.7-19.4]), starting therapy with dopamine agonists and subsequent transsphenoidal surgical treatment (subtotal resection), with an anatomopathological diagnosis of prolactinoma. Subsequently, prolactin levels returned to normal (8.48 mg/dl) and the follow-up pituitary MRI revealed a marked reduction in the size of the pituitary tumor (9×9×8mm). Visual acuity improved remarkably, as did the symptoms of concomitant hypopituitarism. A new control MRI (2021) showed persistence and progression (17×19×15mm) of the adenoma, with new compression of the optic chiasm despite continued treatment with DA, maintaining, however, prolactin levels within normal limits (13.2 mg/dl). The patient underwent surgery again by endoscopic transsphenoidal resection. The histological study showed, on this occasion, immunostaining positive for gonadotropins (LH and FSH), but negative for HGH, ACTH, TSH, and prolactin. These findings allow us to provide an explanation for the lack of response to treatment in DAs.

Conclusion and discussion: Our results would confirm the diagnosis of a metachronous macroprolactinoma with a gonadotropin-producing macroadenoma. Infrequent association (60 cases described to date), whose etiopathogenic basis would lie in the appearance of two adenohypophyseal or intraadenomatous monoclonal expansions.