In vivo secretory potential and the effect of combination therapy with octreotide and cabergoline in patients with clinically non-functioning pituitary adenomas

BACKGROUND The secretory capacity, in vivo, of clinically non-functioning p ituitary adenomas may possibly predict tumour volume reduction during inten sive medical therapy. DESIGN Ten patients (mean (range) 53 years (26-73)) with clinically non-fun ctioning macroadenomas, greater than or equal to 10 mm were studied. The se cretory capacity of the adenomas was examined using basal, NaCl and TRH-sti mulated LH, FSH and alpha -subunit levels. The effect on tumour volume of 6 months' therapy with the combination of a somatostatin analogue, octreotid e 200 mug x 3/day and a dopamine-D2-agonist, cabergoline 0.5 mg x 1/day was studied. The basal LH, FSH and alpha -subunit levels were determined befor e and during 6 months' therapy with octreotide and cabergoline, and MR scan s were used to evaluate tumour volume before and during this period of ther apy. Octopus-perimetry was used to examine the visual fields. RESULTS A reduction in tumour volume (mean +/- SEM (range); 30% +/- 4% (18- 46%)) during 6 months of combination therapy with octreotide and cabergolin e was recorded only in patients with in vivo secretory potential. Tumour vo lume was not reduced in four patients: in three of these patients it remain ed unchanged while in one patient it was observed to have increased (by 14% ). Of the six patients with pretherapy secretory capacity, one displayed a very high basal level of alpha -subunit (74 mug/l) despite unmeasurable lev els of LH and TSH, and an FSH-level of 1 IU/l. The other five patients pres ented paradoxical LH, FSH and/or alpha -subunit responses to TRH. A reducti on in basal levels of LH, FSH and/or alpha -subunit was observed in all six patients, and the maximum reduction of at least one of the hormonal levels was 66% +/- 7% (50-98%). The basal levels of LH, FSH and alpha -subunit in the 10 patients were (mean +/- SEM (range)), 3.0 IU/l +/- 1.0 (0.0-7.4), 1 2.7 IU/l +/- 5.0 (0.0-39.0) and 9.0 IU/l +/- 7.0 (0.2-74.0). During six mon ths of therapy with octreotide and cabergoline, the basal levels of LH, FSH and alpha -subunit were reduced by greater than or equal to 50% in seven p atients - including the six patients with in vivo secretion prior to therap y. No new visual field defects were detected during therapy and no deterior ation of existing visual field defects was recorded. The medical therapy wa s well tolerated. CONCLUSION The in vivo basal and TRH-stimulated secretory capacity of LH, F SH and alpha -subunit predicted tumour reduction following intensive medica l therapy in all of our patients with non-functioning pituitary adenomas.