Endocrine Abstracts

Background: Neurosurgery is treatment of choice in patients with GH-secreting pituitary adenoma. However, in about 50% of cases surgery is ineffective or contraindicated. Long-acting somatostatin analogues are possible, although expensive therapeutic alternative. Generally, 60–70% of patients with active disease responds to such medical treatment.

Aim: Aim of this study was to identify factors influencing medical treatment outcome and to determine if testing injection of 100 mcg octreotide s.c. (SHort Octreotide Test – SHOT) may be used as predictive tool.

Material: Material consisted of 137 patients (88 F and 49 M) aged 17–83 years (mean 49.6) with active acromegaly, treated 2001–2005 in one center. Neurosurgery was primary therapy in 48 cases.

Methods: SHOT: GH assessed in 30 min intervals during 2 h acute 100 mcg octreotide s.c. test. Treatment initiation: GH and IGF-1 concentrations were determined at 1, 3, 7, 14 and the 28 day following test dose 20 mg of OCT-LAR i.m. Prolonged treatment: GH and IGF-1 assessments were performed quarterly during 2–5 years of medical treatment. Imaging (MR) was performed yearly and KNOSP scale was assessed.

Results: Significant reduction of GH concentration (by more than 75%) was achieved in 48 out of 137 cases (35%) SHOT suppressed GH below 2 ng/ml, but in 93 (68%) GH reduction by more than 75% was achieved. Administration of the first OCT-LAR dose suppressed GH below 2 ng/ml in 44 patients (32%) and in 93 (68%) by more than 75%, whereas the IGF-1 levels dropped to age–sex reference range in 39 cases (28%). Most pronounced reduction of GH level (mean drop from 26.2 to 10.8 ng/ml) was registered at the 14th day following the OCT-LAR. During prolonged treatment, GH and IGF-1 levels decreased slowly during first year, and then remained stable (mean 8.3 ng/ml S.D. 5.7 and 497 ng/ml S.D. 312 for GH and IGF-1, respectively). IGF-1 normalization were achieved in 76 (55%). Reduction of GH levels in SHOT tightly correlated with the GH level during long-term treatment (R=0.68, P<0.001). Assessment of GH and IGF-1 during first month of therapy has no additional value. Reduction of GH below 2 ng/ml defines cohort of most probable IGF-1 normalization (sensitivity (sen.) 96% and specificity (spe.) 95.5%), whereas by >75% precisely predicts good outcome of long term therapy (sen. 97% and spe. 70%). Other, independent factors of good outcome is symptoms duration <10 years (sen. 72% spe. 65% and KNOSP grade <3 sen. 63% spe. 48%).

Conclusions: SHOT is effective in identification of cohort with favourable prognosis of pharmacological treatment efficacy.