Endocrine Abstracts

The thyrotroph tumors or pituitary neuroendocrine tumors (PitNET) classify as tumors of Pit-1 family. These tumors are rare and may be monohormonal, secreting only TSH, or plurihormonal, secreting TSH-GH±PRL, with or without acromegaly. The objectives of this retrospective study were to confirm the frequency of the plurihormonal subtype and to compare the clinical, biological and pathological characteristics of these two pathological subtypes. We retrospectively studied the medical records of 23 patients with thyrotroph tumors treated by transphenoidal surgery. Routine staining and immunohistochemistry with the following antibodies against the hormones (PRL, GH, ACTH, βFSH, βLH, βTSH, and α-subunit), the somatostatin receptors (SSTR_2A, SSTR₅), and the transcription factor Pit-1 were performed. The proliferative rate (mitoses and Ki-67 index) and the p53 expression were also studied. The pituitary tumors were classified taking into account the invasion and the proliferation. All the tumors, except one with clinical and biological hyperthyroidism, expressed TSH. Half were monohormonal (n=11) and out of the 12 plurihomornal ones, 6 were positive for both TSH and GH. Two tumors expressed TSH, PRL and GH and 4 were positive for TSH and PRL. Only 3 patients with GH co-expression presented clinical and biological signs of acromegaly. Three TSH monohormonal tumors are silent. The symptoms of hyperthyroidism and goiter were more frequent in the plurihormonal tumors than in the monohormonal ones probably due to GH effect on thyroid facilitating the goitre occurrence. Almost all the thyrotroph tumors expressed Pit-1 and SSTR_2A with a high score (>5). Monohormonal and plurihormonal TSH-PRL tumors were characterized by polymorphous cells, a high expression of SSTR_2A, but no or low expression of SSTR₅. The plurihormonal TSH-GH±PRL subtype (n=8) had a higher expression of both SSTR_2A and SSTR₅ and 4 of them exhibited cytological features of the somatotroph type. Fibrosis and calcifications were frequent in both tumor types. We did not observe differences regarding the proliferative rates and the grading of the tumors. In conclusion, this study confirms that these tumors, belonging to the Pit-1 family, are frequently plurihormonal, secreting mainly TSH-GH, and express SSTRs. The first line therapy is the transsphenoidal surgery, but complementary treatment by somatostatin analogues may be proposed, according to the expression of SSTRs by the tumor.