Endocrine Abstracts

Background: Signal intensity in T2 weighted (w) MRI in somatotroph pituitary adenomas has been described to correlate with histological granulation pattern. Long-term somato-statin analogue (SSA)-response is associated with both histological subtype and T2wMRI.

Objective: To describe secretory baseline characteristics in newly diagnosed acromegalic patients in relation to T2 signal intensity. Moreover, to test whether T2 w images could predict preoperative SSA-response.

Design/patients/methods: Retrospective observational cohort study. Forty-seven patients with newly diagnosed acromegaly were included and classified in three categories accord-ing to signal intensity in T2 w MRI; hypointense, isointense and hyperintense. Baseline IGF1 and GH, and GH response to SSA test were recorded. Long-term response of SSA on tumour volume and invasiveness (SIPAP-score) were analyzed in a subgroup of 25 pa-tients pretreated medically prior to surgery. Histological granulation pattern was evaluated.

Results: Of 14 (30%) adenomas were hypointense, 12 (26%) isointense, and 21 (45%) hyperintense. Median IGF1 (ratio IGF1/ULN) was 3.3, 3.4 and 2.1 in the hypointense, isointense and hyperintense group respectively (P<0.05 for difference between groups). Corresponding values for GH were 43.8, 40.4 and 13.6 mU/l (P<0.05). The response to SSA test dose (% reduction in GH) was 86%, 83%, 69% (P=0.05). There was no significant difference between groups in tumour volume (n=47) or tumour volume reduction in patients pretreated with SSA (n=25). Median reduction in SIPAP-score after SSA-treatment was 0.5, 2 and 0 (P<0.05).

All eight sparsely granulated adenomas were hyperintense on T2 w images.

Conclusions: T2 hyperintense tumours had lower GH and IGF1 values at baseline and a reduced SSA responsiveness in an acute test. The effect of SSA treatment on tumour invasiveness in hyperintense adenomas is small.

T2 w MRI signal intensity in newly diagnosed acromegaly might improve stratification in relation to medical therapy.