Endocrine Abstracts

Introduction: Moderate hyperprolactinaemia occurring in a patient with a normal pituitary MRI, assuming macroprolactin and stress are excluded, is generally considered to be due to a lesion below the level of detection of the MRI scanner. Most patients with mild-moderate hyperprolactinaemia and a normal MRI respond to dopamine agonist therapy. We describe a patient who had prolactin elevation typical of a prolactin-secreting macroadenoma, but with a normal MRI, and in whom the prolactin rose further with dopamine agonist treatment.

Case: A 46 year-old female presented with 12 months history of secondary amenorrhoea without galactorrhoea. Prolactin was 4746 mIU/l without macroprolactin complexes, LH & FSH were low and oestradiol was undetectable. She had normal visual fields and no other clinical or biochemical features of pituitary dysfunction. She was not on regular medication. Pituitary MRI was normal with no focal lesion. She was started on cabergoline 250 mcg twice weekly which was subsequently increased to 500 mcg twice weekly. Repeat serum prolactin 5 months and 8 months later showed a progressive rise to 6649 mIU/l and 9653 mIU/l respectively, and rose to 11,611 mIU/l. Compliance with medication was confirmed. Repeat pituitary MRI scan was normal. An alternative source of prolactin was considered and further clinical assessment revealed a palpable pelvic mass. Pelvic CT showed an 11 cm uterine mass which raised the possibility of an ectopic prolactin source. She underwent surgical resection. Histological examination showed a benign Uterine Tumour Resembling Ovarian Sex Cord Tumours (UTROSCT). Immunohistochemistry was negative for prolactin, however, serum prolactin postoperatively was 59 mIU/L and her menstrual cycle returned to normal.

Discussion: The notable features of this case were (1) the high prolactin suggestive of a macroadenoma with a normal MRI scan (2) a paradoxical rise in the serum prolactin after initiation of dopamine agonist therapy. Out of eight previous reports of ectopic extra-cranial prolactin secretion in the published literature, there are three ovarian germ cell tumours (two teratomas, one dermoid) which had microscopic pituitary elements. UTROSCTs are very rare uterine neoplasms with the most literature review citing 77 cases. UTROSCTs have not been associated with hyperprolactinaemia prior to this report. However, two other cases have been reported with uterine tumours (one “fibroid” and one “mesenchymal tumour”) which share characteristics with this case. Hyperprolactinaemia due to extra-cranial ectopic prolactin production is very rare. Where suspected, the majority of ectopic prolactin-secreting tumours have been located in the ovaries and uterus.