Introduction: Silent somatotroph tumors (sST) are a pituitary neuroendocrine tumor subtype with positive immunostaining for growth hormone (GH) but without the presence of acromegaly. Unlike silent corticotroph tumors, there is little information in the literature on sST. The aim of the present study was to study the demographic, clinical and molecular characteristics in a series of ST in order to compare sST and functioning ST (fST).
Methods: We have studied 72 ST. Immunohistochemically 62 fST and 10 sST have been identified. The immunohistochemistry was performed with the anti-GH polyclonal antibody of Novocastra and the quantification of GH and PRL gene expression was carried out by quantitative PCR with TaqMan probes. The following variables were evaluated: gene expression of GH and PRL, gender, age, maximum tumor diameter, ki67, pre-surgical IGF1 and invasiveness.
Results: fST showed higher gene expression of GH and PRL (P<0.001, P=0.032, respectively) and higher levels of pre-surgical IGF1 (P<0.001). On the other hand, sST presented higher maximum tumor diameter (P=0.010). No differences were found between fST and sST according to gender, age, ki67 and invasiveness (all P>0.05).
Conclusion: fST express more GH and PRL than sST and presented higher levels of pre-surgical IGF1. By definition, there are changes in tumor diameter since all sST are macroadenomas. On the contrary, there are no differences in the invasiveness behavior. Age and gender do not contribute to the functionality of this subtype.
18 - 21 May 2019
European Society of Endocrinology