Reversible shrinkage of a growth hormone-secreting pituitary adenoma by a long-acting somatostatin analogue, octreotide

Octreotide acetate (SMS-201-995), a somatostatin analogue, was used to treat an acromegalic patient harboring a growth hormone-secreting pituitary macroadenoma. Intermittent subcutaneous administration of octreotide suppressed growth hormone and insulin-like growth factor-I (IGF-I) levels and ameliorated clinical symptoms. Magnetic resonance imaging performed after 16 weeks revealed a 70% shrinkage of the pituitary mass, with a resultant partially empty sella turcica. To document that this shrinkage occurred as a result of octreotide treatment and not spontaneous tumor infarction, the medication was withdrawn for 4 weeks. A second magnetic resonance image disclosed regrowth of the tumor accompanied by rebound of growth hormone and IGF-I secretion. Subsequent biochemical remission has been sustained with preservation of anterior pituitary function since the drug was reinitiated. These findings suggest that intermittent subcutaneous administration of octreotide may provide potent medical ablation of growth hormone-secreting macroadenomas.