Absence of a suppressive effect of 2-hydroxyestrone on hyperprolactinemia in patients with prolactinomas before and after estradiol administration.

The effect of the infusion of 2-hydroxyestrone (125 micrograms/h for 8 h) on plasma PRL levels was investigated before and 64 h after the administration of 1 mg estradiol benzoate in five patients with PRL-secreting pituitary adenomas. There was no effect on the circulating PRL levels measured hourly for 8 h during both episodes of 2-hydroxyestrone infusion, but plasma LH and FSH levels were suppressed. Infusion of 2-hydroxyestrone in two hyperprolactinemic patients with craniopharyngeomas also did not change the circulating PRL levels. We conclude that: 1) 2-Hydroxyestrone does not suppress PRL levels in patients with prolactinomas. This is not caused by the low estrogenic state of these patients, because 2-hydroxyestrone remained ineffective after the administration of estradiol. 2-Hydroxyestrone was also not able to suppress the estradiol-induced stimulation of PRL release. 2) 2-Hydroxyestrone does not diminish PRL levels in patients with suprasellar tumors and hyperprolactinemia. Therefore, infusion of 2-hydroxyestrone cannot be used in the differential diagnosis of hypothalamic and tumoral hyperprolactinemia.