REMISSION OF ACROMEGALY CAUSED BY PITUITARY CARCINOMA AFTER SURGICAL EXCISION OF GROWTH HORMONE-SECRETING METASTASIS DETECTED BY 111-INDIUMPENTETREOTIDE SCAN

GH-secreting carcinomas of the pituitary are extremely rare. We descri be a 37-yr-old woman with refractory acromegaly 15 yr after transpheno idal surgery and radiotherapy, with no evidence of a recurrent pituita ry mass. Scanning with Ill-indium pentetreotide revealed an area of in tense activity in the left neck. A 3.5 x 2.5-cm mass was excised from the neck after demonstrating an arterio-venous GH gradient of 7:1. GH levels (50 ng/mL) dropped to 0.8 ng/mL 3 h after surgery and remained normal. GH gene expression was demonstrated in the metastasis by North ern and Western blot analyses and by positive immunocytochemistry and immunoelectron microscopy. In vitro cultured cells responded to GHRH a nd TRH by increasing GH levels (P < 0.01). Medium GH was identical to authentic pituitary GH, as demonstrated by high pressure liquid chroma tography. RT-PCR of hypothalamic hormone receptor messenger RNA in the mass revealed somatostatin receptor subtypes 2, 3, and 5 and GHRH, TR H, and dopamine receptor expression. No GH gene amplification, rearran gement, or gsp mutation was found. RE gene deletion and H-ras mutation s, previously reported in PRL- and ACTH-secreting carcinomas, were not detected. In conclusion, clinical and molecular features of a GH-secr eting pituitary carcinoma are presented. This metastatic lesion synthe sized GH and expressed functional hypothalamic hormone receptors.