WITHDRAWAL OF BROMOCRIPTINE AFTER LONG-TERM THERAPY FOR MACROPROLACTINOMAS - EFFECT ON PLASMA PROLACTIN AND TUMOR SIZE

The present study describes the effect on plasma prolactin values and tumour size of bromocriptine withdrawal in 12 patients who had been treated for macroprolactinomas for a period of 3.5-7 (mean 4.9) years. Pretreatment plasma prolactin values ranged from 12 000 to 210 000 (mean: 66 000) mU/I. Immediately before bromocriptine withdrawal plasma prolactin values were in the normal range (< 350 mU/I for men; < 450 mU/I for women). Bromocriptine treatment was associated with tumour reduction in all cases. The following observations were made upon withdrawal of bromocriptine: (1) In 11 patients hyperprolactinaemia redeveloped although plasma prolactin levels remained below 600 mU/I in two of these patients during a follow-up period of 1 year. In the other nine patients bromocriptine treatment was reinstituted after 4-12 weeks. (2) Hyperprolactinaemia was associated with tumour re-expansion in one case and increased density of the tumour in two cases. (3) In one patient plasma prolactin remained undetectable during a follow-up period of 1 year and no tumour re-expansion was found. In is concluded that tumour regrowth is uncommon and of small extent after cessation of long-term bromocriptine treatment for macroprolactinomas.