Endocrine Abstracts

Introduction: Prolactinoma are the commonest functioning pituitary tumors. Pressure symptoms such as headache and visual field defect are common in patients with macroprolactinoma. Early investigation and intervention can deter permanent visual impairment, pituitary apoplexy and panhypopituitarism.

Case vignette: 27-year-old lady presented to ophthalmologist with two months history of headache with visual impairment on the right side. She was found to have Inferior-nasal quadrantanopia, reduced colour vision and relative afferent pupillary defect on right side. CT brain showed 29 x 28 x 23 mm sellar and right parasellar hyperdense lesion. Subsequently, MRI pituitary confirmed the sellar mass had appearances in keeping with a macroadenoma compressing of the right pre-chiasmatic optic nerve. It also protruded into sphenoid sinus, right cavernous sinus and partially encased cavernous carotid artery. She was referred to Endocrinology team. She did not have any galactorrhoea and was otherwise asymptomatic. She used progesterone only pill continuously to avoid menstruation. Baseline blood tests showed Prolactin of 124250 mU/l(ULN - 496mU/l), FSH 0.7 IU/l(Low), LH <0.3 IU/l(Low), Oestradiol 18 pmol/l(Low). IGF-1, cortisol, thyroid function and routine bloods were normal. Cabergoline 500 micrograms twice weekly was initiated with the counseling on the risk of CSF rhinorrhoea with rapid tumour regression and risk of disinhibition with dopamine agonist therapy. Her Prolactin level reduced significantly (23 folds) in four weeks. Headache improved significantly but gonadotrophins and oestradiol remained low. After 4 months, her prolactin level normalized and gonadotrophins were starting to rise. Her colour vision and visual field dramatically improved. Repeat MRI demonstrated reduced tumour volume and regression away from the pre-chiasmatic optic nerves and optic chiasm. Her genetic test result for multiple endocrine neoplasia type 1 is still pending but there is no evidence of other clinical manifestation to date.

Discussions: • Macroadenomas can have varying appearance on CT and MRI is the gold standard imaging test to confirm the diagnosis

• Massive macroprolactinoma in a young patient (<30yr) prompts for genetic testing.

• Women of child bearing age taking POP pill could mask menstrual disturbances caused by prolactinoma and may delay early diagnosis

• Although galactorrhoea is a common presentation (80-90%) of prolactinoma, it was not present in our patient despite a large macroprolactinoma with prolactin level more than 250 times above normal range.

• Dopamine agonist therapy is safe and well tolerated by most but patients should be counselled on associated risks of the medication itself and effects on tumour size