Cabergoline decreases somatotroph adenoma size: a case report

Dopamine agonists have been shown to reduce growth hormone secretion in some patients with acromegaly, but their effect on adenoma size has not been well appreciated. We describe a 69 year-old woman with acromegaly caused by a somatotroph macroadenoma who received primary treatment with the dopamine agonist cabergoline. Two months after beginning cabergoline, she experienced soft tissue regression and normalization of the serum IGF-1 concentration that persisted for the remainder of the 25 months of observation. By 13 months, the volume of the adenoma by MRI was 28% of its pretreatment size, and by 25 months it was 24%. This case demonstrates that when cabergoline decreases substantially the serum IGF-1 concentration of a patient with a somatotroph macroadenoma, the adenoma size may also decrease substantially. This demonstration, plus the ease of oral administration, suggests that it would be worthwhile to study systematically the effect of cabergoline on the size of somatotroph macroadenomas.