Endocrine Abstracts

Prolactinomas usually present because of reproductive/sexual dysfunction due to the hyperprolactinemia but they may also present because of mass effects. Prolactin (PRL)-secreting microadenomas enlarge in only about 7% of cases, so many can be followed without direct treatment, although sex steroid hormone replacement may be required. Dopamine agonists can normalize PRL levels in over 90% of cases and can reduce tumor size significantly in over 75%, with cabergoline being generally more efficacious in both regards and also better tolerated. Thus, dopamine agonists are the treatment of choice with better success rates compared to transsphenoidal surgery. Uncommonly, some patients are resistant to dopamine agonists and may require switching from bromocriptine to cabergoline or larger than usual doses of cabergoline. Very high doses (about 10-fold higher than usual) of cabergoline in Parkinson’s disease patients may cause cardiac valvular abnormalities but this has not been the case with doses conventionally used for prolactinoma patients, except in one study. Routine echocardiography is not necessary when conventional doses are used but may be helpful in surveillance of patients taking more than 2 mg/week. Dopamine agonists are usually stopped once a woman has become pregnant and no excess fetal abnormalities have been found with either bromocriptine or cabergoline compared to the normal population, although the safety database for bromocriptine is about 10-fold larger than that for cabergoline. The high estrogen milieu of pregnancy plus the discontinuation of the growth-inhibiting dopamine agonist results in clinically significant enlargement in 2.5% of patients with microadenomas and about one-third of those with macroadenomas. For patients with large macroadenomas, options include stopping the dopamine agonist when pregnancy is diagnosed, continuing the drug through the pregnancy, or prepregnancy debulking. If the tumor enlarges significantly, options include delivery if the pregnancy is far enough advanced, restarting the dopamine agonist, or surgical debulking.

Generously supported by the Clinical Endocrinology Trust.