SSTR2 and non-functioning pituitary adenoma: ,10 The expression of somatostatin receptors (SSTR) in the majority of NFPA provides a further potential target for receptor-mediated therapy with somatostatin analogues (SSA).11, 12, 13, 14, 15, 16 SSTR subtypes found most commonly in NFPA samples are SSTR2, SSTR3, and SSTR5, all three of which are implicated in antiproliferative effects.11, 12, 13,15,17In vitro studies have demonstrated inhibition of cell viability and proliferation in response to octreotide and lanreotide, two first-generation SSAs with highest affinity for SSTR2.18