EFFECTS OF OCTREOTIDE ON MORPHOLOGY OF PITUITARY-ADENOMAS IN ACROMEGALY

We studied the effects of the long - acting somatostatin analogue octr eotide (SMS 201-995, Sandoz, Basel, Switzerland) on the morphology of pituitary adenomas in acromegaly. Of the 29 adenomas examined by light microscopy, 16 had been treated pre-operatively with octreotide. The treated adenomas were compared with the untreated adenomas. 14 adenoma s were also studied by electron microscopy. In 23 cases we performed i n-situ-hybridization for GH-mRNA. Under light microscopy, we found a d ecrease in amyloid deposits and a higher amount of cell necroses and f ibroses after treatment, mainly in the tumors with shrinkage. Tumor sh rinkage was diagnosed when the maximal diameter of the adenoma decreas ed for at least 113 during octreotide treatment in NMR examination. Im munohistochemical examinations showed that treated adenomas, especiall y those with tumor shrinkage, possessed more GH immunoreactive cells, and after in-situ-hybridization we found a higher content of GH-mRNA. On the ultrastructural level, rough endoplasmic reticulum appeared to be increased in treated adenomas. The increase of GH-mRNA and of rough endplasmic reticulum suggests the likelihood of an increased secretor y activity due to a rebound effect after short-term pre-operative omis sion of octreotide. Other findings are discussed.