Endocrine Abstracts

Background: Somatotroph PitNETs represent a polymorph group of GH-secreting pituitary neuroendocrine tumors with great variety of clinical presentation, which may graduate from totally silent without clinical and biochemical signs of hormonal hypersecretion to functioning with subtle or classic acromegaly symptoms. The grade of GH and somatostatin receptors expressoin as well as the other pituitary hormones and receptors co-expression may contribute to the tumor biological behavior.

Objective: To discover the clinical profile of silent and subclinical somatotroph PitNETs according to the immunohistochemical staining.

Materials and Methods: We have conducted a retrospective analysis of 33 cases of GH-immunopositive PitNETs surgically resected in our center without clinical signs of acromegaly. Tumors were classified according to the immunohistochemical staining: pure somatotroph, mammosomatotroph, mixed somatotroph-lactotroph, somatotroph-thyrotroph, plurihormonal Pit-1- lineage tumors. The clinical presentation and the grade of GH, somatostatin and estrogen receptors expressoin were compared in these groups.

Results: Silent somatotroph PitNETs represented 10·4% from all consecutive cases of nonfunctional PitNETs and 21.8% of all cases of GH-positive PitNETs. Pure somatotroph tumors constituted 48·5% of all GH-positive tumors, mammosomatotroph – 12·1%, mixed somatotroph-lactotroph – 21·2%, somatotroph-thyrotroph – 12·1%, plurihormonal Pit-1- lineage tumors – 6% respectively. Pure somatotroph tumors were divided into 2 groups: totally silent (24·25%) and subclinical (24·25%). The prevalent symptoms in cases of totally silent GH-tumors were visual disturbances and oligomenorrhea/amenorrhea. Headache was the most frequent presenting complaint in mixed somatotroph-lactotroph tumors. The presence of hypopituitarism and invasiveness depended on the immunohistochemical type of the tumor. The grade of GH expression didn’t correlate with somatostatin receptors expression. The SSTR2 and SSTR5 expression was negative or lower than in acromegaly. All silent somatotroph tumors were negative for estrogen receptors.

Conclusions: Clinical presentation of silent somatotroph PitNETs is variable and depends on the variant of the immunohistochemical staining.