Medical Therapies in Functioning Pituitary Neuroendocrine Tumors(PitNETs)

Abstract

Transsphenoidal surgery is the first-line treatment for most functioning pituitary neuroendocrine tumors(PitNETs). Medical therapies are usually chosen for patients with residual or refractory tumors after surgery or contraindications to surgery. Dopamine agonists(DA)are the first-line treatment for prolactinomas. Somatostatin analogs are the first line of therapy for GH- and TSH-producing PitNETs. In severe hypercortisolemia due to ACTH-producing PitNETs, adrenal enzyme inhibitors such as 11β-hydroxylase inhibitors should be started immediately, as marked hypercortisolemia leads to serious opportunistic infections. Pasireotide and DA are usually administered to treat mild hypercortisolemia. Based on the histological pattern of secretory granules, somatotroph, lactotroph, and corticotroph tumors can be divided into two subtypes: densely granulated and sparsely granulated. Densely granulated lactotroph tumors tend to be resistant to DA. In contrast, densely granulated somatotroph and corticotroph tumors express high levels of somatostatin receptors and are more responsive to somatostatin analogs. Since ACTH-producing PitNETs express SSTR5 without SSTR2, the second-generation somatostatin analog, pasireotide, is effective against ACTH-producing PitNETs.