Medical treatment of prolactinomas.

Prolactinomas, the most prevalent type of neuroendocrine disease, account for approximately 40% of all pituitary adenomas. The most important clinical problems associated with prolactinomas are hypogonadism, infertility and hyposexuality. In patients with macroprolactinomas, mass effects, including visual field defects, headaches and neurological disturbances, can also occur. The objectives of therapy are normalization of prolactin levels, to restore eugonadism, and reduction of tumor mass, both of which can be achieved in the majority of patients by treatment with dopamine agonists. Given their association with minimal morbidity, these drugs currently represent the mainstay of treatment for prolactinomas. Novel data indicate that these agents can be successfully withdrawn in a subset of patients after normalization of prolactin levels and tumor disappearance, which suggests the possibility that medical therapy may not be required throughout life. Nevertheless, multimodal therapy that involves surgery, radiotherapy or both may be necessary in some cases, such as patients who are resistant to the effects of dopamine agonists or for those with atypical prolactinomas. This Review reports on efficacy and safety of pharmacotherapy in patients with prolactinomas

Cabergoline

Cabergoline (CAB) (1-[(6-allelylergolin-8 beta-yl)carbonyl]-1-[3-(dimethylamino)propyl]-3-ethyl-urea) is an ergoline derivative with potent, selective and long-lasting inhibitory activity on prolactin (PRL) secretion acting on dopamine receptors present in pituitary lactotrophes. Receptor binding studies have demonstrated that CAB has high in vitro selectivity and affinity for the subtype D2 of the dopamine receptor. In cultures of rat anterior pituitary cells, the concentrations of CAB and bromocriptine required to inhibit PRL secretory activity by 50% (IC50) were 0.1 and 3.4 nmol/l, respectively. As compared to bromocriptine, CAB was more potent in inhibiting the binding of [3H]N-n-propylnorapomorphine and it occupied the receptor for longer. These effects were observed in all areas of the rat brain. In vivo, CAB at doses of 0.125-1 mg twice weekly caused a dose-dependent suppression of PRL secretion in women with hyperprolactinaemia. CAB was shown to be significantly more effective than bromocriptine in inducing a complete biochemical response and clinical efficacy and was better tolerated than bromocriptine in the majority of patients. Notable tumour shrinkage until tumour disappearance was observed during CAB treatment in most patients with macroprolactinoma. CAB was also shown to be effective in patients resistant or poorly responsive to bromocriptine. In view of the limited data on CAB-associated pregnancies and the long half-life of the drug, it is currently recommended that women seeking to became pregnant, once ovulatory cycles have been established, should discontinue CAB therapy 1 month before they intend to conceive. However, no data on negative effects on pregnancy or offspring have been reported. The great efficacy of CAB together with its excellent tolerability makes this drug the current treatment of choice for the majority of patients with hyperprolactinaemic disorders. Very recently, the efficacy of CAB treatment has been reported in patients with acromegaly and clinically non-functioning adenomas with controversial results. CAB was also reported to have some efficacy in patients with Nelson's syndrome and Cushing's disease although these data are available only for limited case reports