Endocrine Abstracts

Background: Giant prolactinomas are rare pituitary adenomas with markedly elevated prolactin levels that can present with diverse neurological and endocrine manifestations. This case highlights an atypical presentation with acute neurological symptoms.

Case: A 52-year-old male presented with an episode of LOC and a generalised seizure, followed by post-ictal confusion with amnesia. An MRI of the head and pituitary demonstrated a large sellar fossa and left middle cranial fossa mass measuring 5.3 × 3.8 × 3.1 cm, causing chiasmal compression and extending into the left cavernous sinus and involving the cavernous segment of the ICA, with associated left temporal lobe oedema. He was commenced on levetiracetam and dexamethasone. Further history revealed reduced libido, and examination showed left temporal visual field loss. His pituitary profile demonstrated marked hyperprolactinaemia (prolactin 177,390 mU/l) and hypopituitarism: testosterone 1.1nmol/l, free testosterone 44pmol/l, LH 2.3 U/l, FSH 4.6 U/l, SHBG 8 nmol/l, free T4 7.2pmol/l, TSH 0.36 mU/l, IGF-1 35.3 nmol/l, OGTT showed a nadir GH of 0.1μg/l and cortisol 16 nmol/l (while on dexamethasone). He was switched to hydrocortisone and commenced on cabergoline 500 mg twice weekly, increased to 500 mg OD, as well as testosterone and levothyroxine. After six weeks, his prolactin level reduced substantially to 1,055 mU/l, and MRI of the pituitary showed a decrease in tumour size.

Discussion: The patient’s acute neurological presentation was attributed to mass effect from the macroadenoma, with temporal lobe oedema. The unilateral visual field defect reflects asymmetric tumour extension. Cabergoline is a first-line medical therapy with high rates of prolactin reduction and tumour shrinkage.

Conclusion: This case highlights the importance of considering pituitary pathology in patients presenting with seizures and visual field defects. Although rare, giant prolactinomas are highly responsive to dopamine agonist therapy, and early recognition leads to excellent outcomes.