Endocrine Abstracts

A 62-year-old man presented with 1 month history of lethargy, nocturia, thirst and diplopia. On examination he had left 3rd nerve palsy with complete ptosis. MRI pituitary demonstrated a 1.3×1.1 cm enhancing mass on the left side of the pituitary gland, with invasion of the left cavernous sinus. Endocrine work up revealed partial DI, TSH and gonadotrophin deficiency. Because of unusual appearance of the pituitary lesions, a biopsy was arranged but initial histology was inconclusive. Routine biochemistry performed pre-operatively showed a raised alkaline phosphatise of 557 U/l (N<130 U/l). He reported severe backache and plain X-ray of the spine showed changes suspicious of Paget’s disease. Bone scan showed increased tracer uptake in skull vault, ribs, pelvis and proximal femora with features consistent with diffuse osteoblastic metastatic deposits rather than Paget’s. PSA was then measured and found to be markedly elevated at 919 μg/l. In light of the PSA result, pituitary biopsy was then stained for PSA and prostate acid phosphatase, which confirmed that the pituitary lesion was metastatic prostatic cancer. Androgen deprivation therapy (ADT) was commenced with cyproterone and long term goserelin acetate, which led to reduction in PSA levels and partial resolution of the 3rd nerve palsy. Repeat MRI of the pituitary showed complete resolution of the pituitary lesion. Intracranial spread of prostate cancer is unusual and pituitary metastasis extremely rare, with only three cases described in the literature so far. Due to its direct blood supply and larger contact area with adjacent dura, posterior pituitary is the preferred site for pituitary metastases. This may cause DI and contiguous spread from the posterior lobe may result in anterior pituitary deficiencies. Infiltration of adjacent cavernous sinus may cause 3rd and, less commonly, 4th cranial nerve palsies. Due to the rarity of pituitary metastasis, there is little evidence for optimum treatment of such lesions. Our patient responded very favourably to ADT. Although rare, Prostate malignancy should be considered in the differential of pituitary lesions due to its potential to respond to medical treatment.