Endocrine Abstracts

A 70 yr old man presented with an episode of syncope and complaints of leg weakness. He was hypogonadal with coarse facial features and a marked proximal myopathy. Hypopituitarism was confirmed biochemically: serum FT4 7.7 pmol/l (9.7-25.7), TSH 1.65 mIU/l (0.05-5.00), FSH 1.8 IU/l (1.6-18.0), LH 1.0 IU/l (2.0-18.0), testosterone 1.13 nmol/l (5.70-28.8) and 9am cortisol 122 nmol/l. Treatment with hydrocortisone and thyroxine was commenced. Further investigation revealed elevated serum prolactin at 16,000 mIU/l (83-500). Basal HGH was 170 mU/l with IGF1 147.0 nmol/l (5.0-22.5) and IGFBP3 9.6 mg/l (0.7-4.40), failing to suppress during an oral glucose tolerance test. An MRI scan of the pituitary confirmed a large tumour (4 x 3.5 cm) co-secreting growth hormone and prolactin. The tumour mass showed diffuse homogenous enhancement and extended into both cavernous sinuses, displacing the pituitary stalk and optic chiasm and causing bilateral upper outer quadrantanopia. Treatment was commenced with Cabergoline 250μg twice weekly, which was tolerated well and titrated up to 500 μg twice weekly after one month with the later addition of androgen replacement therapy. A subsequent short synacthen test was normal and hydrocortisone was withdrawn. There was a good clinical response to treatment and serum prolactin declined to 199 mIU/l within two months. A repeat MRI scan five months after initiation of treatment showed a 75% reduction in tumour size, dramatic reduction of suprasellar and cavernous sinus extension and clear visibility of the optic chiasm. This case demonstrates the effectiveness of initial treatment with Cabergoline in reducing tumour size in a patient with a large pituitary tumour co-secreting both prolactin and GH, a raises significant questions as to the optimal further management.