Endocrine Abstracts

Case history: A 20-year-old male presented with a one-year history of reduced libido, headache and slowly progressive blindness. His symptoms (particularly the visual deterioration) had a great impact on his daily life, leading to dismissal from work. Examination showed decreased visual acuity (12/6 bilaterally), reduced colour vision and a dense bitemporal visual field loss. Testes measured 15 mls bilaterally. He had no clinical stigmata of acromegaly, nor Cushing’s disease. Other systems’ examination was unremarkable.

Investigations: Routine laboratory investigations (full blood count, kidney, liver and bone functions) were unremarkable. Baseline pituitary function test showed a significantly raised serum prolactin level of 57 000 [reference range: 50–500 mU/l]. Ancillary lab tests excluded the presence of macroprolactin in the sample. The rest of the pituitary blood tests were within the normal range. Pituitary MRI showed a large sellar mass invading a significant portion of the skull base, extending superiorly to compress the optic chiasm and laterally to invade both cavernous sinuses.

Results and treatment: Based on the imaging and the biochemistry data, a diagnosis of large macroprolactinoma was made and the patient was started on a titrated dose of cabergoline therapy (initial dose: 250 μg twice weekly). He tolerated the treatment very well with no side effects despite gradual dose escalation to 1 g thrice weekly. After six months of treatment, his vision had dramatically improved and his serum prolactin decreased to 4500 mU/l. This was associated with a rapid reduction in tumour size to more than 50% of the initial measurement. A skull base computed tomography (CT) scan showed areas of bony defects that were occupied by tumour tissue. A decision was made to reduce the cabergoline dose to avoid the possibility of cerebrospinal fluid (CSF) leakage due to skull defects.

Conclusions: In macroprolactinomas that are structurally very sensitive to DA therapy, careful down-titration of the DA dose is crucial to avoid CSF leaks. CT scanning is informative in the assessment of skull base integrity and may inform decision making regarding DA dose adjustment.

Points for discussion: •  DA dose titration/adjustments based on imaging data in prolactinomas

•  CT skull base interpretation and recognising potential areas of CSF leakage