Cabergoline monotherapy in GH- and PRL-cosecreting pituitary adenomas.

Functional pituitary tumours, also called pituitary neuroendocrine tumours (PitNETs), typically produce a single hormone, based on the cell lineage from which they arise in the anterior pituitary. Pituitary adenoma dual hypersecretion is less common and may present management dilemmas. Prolactin (PRL) and growth hormone (GH) co-secreting pituitary adenomas (GH and PRL-PA) are the most common form of pituitary adenoma dual hypersecretion, arising from PIT1-lineage PitNETs, most commonly mammosomatotroph and mixed somatotroph-lactotroph adenomas. Pharmacotherapies employed in prolactinoma (i.e. dopamine agonists) and acromegaly (e.g. somatostatin analogues) may be used in GH and PRL-PA, in addition to transsphenoidal surgery. However, the ideal treatment of this rare PA subtype is unknown, reflected by a lack of specific treatment recommendations in both acromegaly and prolactinoma guidelines. Herein, we present an individual with a giant GH and PRL-PA with complete biochemical (GH and PRL), and partial structural, ophthalmological and clinical, responses to upfront cabergoline monotherapy. This case, along with previous data showing GH and structural responses to cabergoline in individuals with acromegaly and hyperprolactinaemia, argue for a role for cabergoline monotherapy in the treatment armamentarium of GH and PRL-PAs, noting that some tumours may exhibit a significant treatment response as observed here. Learning points: GH and PRL-PA is a typically aggressive form of pituitary adenoma.Cabergoline monotherapy can be an effective treatment option for select case of GH and PRL-PA, resulting in both biochemical and structural responses.Some GH and PRL-PAs may exhibit a 'hyper-response' to cabergoline with rapid, profound hormone reduction and/or tumour shrinkage.