Efficacy of the long-acting octreotide formulation (octreotide-LAR) in patients with thyrotropin-secreting pituitary adenomas.

Abstract

The presence of somatostatin receptors on TSH-secreting pituitary adenomas allows treatment of central hyperthyroidism with somatostatin analogs. Six women and 5 men (mean +/- SEM age, 43 +/- 3 yr) presented TSH-secreting pituitary adenomas (micro, n = 2; macro, n = 9). Seven patients had previously been treated with partial surgical removal (n = 6) and/or external radiation (n = 4) of their adenoma at least 1 yr before the study, whereas 4 patients had not been treated before somatostatin analog therapy. TSH, free T(4), and free T(3) levels were in the normal range during treatment with sc injections (n = 9) or continuous infusion (n = 2) of octreotide (280 +/- 25 microg/day). Mean thyroid hormone levels increased (P < 0.01) after the washout period (34 +/- 6 days). The patients received monthly im injections of 20 mg Octreotide-LAR. In patients with an elevated free T(4) level after 3 months (n = 1) the Octreotide-LAR dose was increased to 30 mg. After 3 months of Octreotide-LAR treatment, TSH, free T(4)/T(3), and alpha-subunit levels decreased, and 10 patients were euthyroid with normal free T(4) levels. These results remained at the same level over the next 3 months. There were no statistically significant differences in the TSH and free T(4) responses to sc octreotide or im Octreotide-LAR between previously untreated patients and patients who had undergone surgical resection and/or pituitary radiation before somatostatin analog treatment. During Octreotide-LAR treatment, minor digestive problems or moderate discomfort at the injection site, lasting less than 48 h, were reported in 6 and 5 patients, respectively. Gallbladder echographies did not reveal new gallstones during Octreotide-LAR treatment. In conclusion, this study shows that monthly im Octreotide-LAR is as effective as daily sc octreotide in controlling hyperthyroidism in patients with TSH-secreting pituitary adenomas, in both previously untreated patients and patients treated with surgery and/or pituitary radiotherapy. Octreotide-LAR is well tolerated, except for minor digestive problems or mild pain at the injection site. Therefore, Octreotide-LAR appears to be a useful therapeutic tool to facilitate medical treatment of TSH-secreting pituitary adenomas in patients who need long-term somatostatin analog therapy.