Endocrine Abstracts

Case history: 21-year-old male presented in November 2006 with visual loss, headaches and fatigue. No previous past medical history. Visual field testing confirmed a left temporal hemianopia with right temporal upper quadrantanopia.

Investigations: Brain imaging revealed a large macroadenoma with suprasellar and lateral extension. Hormone testing demonstrated abnormalities in TSH 5.13 mU/L, Free T4 7.1 pmol/l, random Cortisol 64nmol/l and Testosterone 2.3nmol/l, with an elevated Prolactin 4661 mU/L (lower than expected for the size of lesion). Cabergoline was initiated from January 2007 in attempt to shrink the tumour prior to surgery, in addition to Hydrocortisone and Levothyroxine replacement.

Results and treatment: By May 2007 there was significant reduction in tumour size following up-titration of Cabergoline. This translated to both subjective and objective improvement in vision, with only a small residual left temporal upper quadrantanopia. Prolactin reduced to 494mU/L. Following MDT discussion, surgery was indefinitely postponed and patient continued on medical therapy. MRI imaging in July 2007 confirmed the lesion was no longer compressing the optic chiasm. Ongoing monitoring demonstrated further radiological shrinkage of the macroadenoma and complete normalisation of visual fields and acuity. In November 2009, the left posterior aspect appeared predominantly cystic and extended into the medial temporal lobe. Cystic degeneration of the lesion continued to increase over the next 7 years, but the patient remained asymptomatic on Cabergoline. In early 2018, he developed increasingly frequent episodes of speech disturbance and lip smacking. Following neurological and neurosurgical assessment, the patient was diagnosed with Temporal lobe epilepsy and initiated on anti-epileptic drugs (AEDs). Further imaging illustrated this was due to formation of a medial temporal meningoencephalocele colliding with the expanding cystic prolactinoma, as a result of dopamine agonist therapy. In November 2018, the patient underwent transsphenoidal repair of the meningoencephalocele and resection of the residual treatment-resistant prolactinoma. Histology confirmed anterior pituitary tissue with a lactotroph predominance. Post-surgery, Prolactin suppressed and seizures were eventually controlled on a reduced combination of AEDs. His Cabergoline has been reduced gradually since late 2021 and as of February 2023, Prolactin remains suppressed.

Discussion: Cabergoline remains first line treatment for macroprolactinomas. Its efficacy in reducing tumour size and normalising Prolactin levels, means only a minority of patients go on to require surgical resection. Cystic degeneration can reflect the impact of dopamine agonist therapy on macroprolactinomas, or may represent tumour infarction. Medical treatment can also unmask skull-base defects.