| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Letters to the Editor |
Department of Internal Medicine and Endocrinology Université Catholique de Louvain at Mont-Godinne University Hospital B-5530 Yvoir, Belgium
To the editor:
Notable discrepancies appear when analyzing the results from various studies assessing treatment outcomes of patients with prolactinomas. Recently, based on a retrospective review of 46 male patients with hyperprolactinemia managed with dopamine agonist (DA) therapy alone, Pinzone et al. (1) conclude that PRL normalization is comparable in male patients with macroprolactinomas vs. those with microprolactinomas. This study also shows that the response rates to bromocriptine (BRC) and cabergoline (CAB) were similar in both groups. This is rather surprising because CAB has been previously reported to be more effective than BRC in normalizing PRL levels in patients with prolactinomas (2) and because macroprolactinomas in men have been shown to be more aggressive tumors with a higher prevalence rate of invasion toward cavernous sinus and resistance to BRC (3). Moreover, this is not in keeping with the results from the large-scale study by Verhelst et al. (2), who found that the probability of reaching normal PRL levels during CAB treatment was significantly higher in patients of both sexes with a microprolactinoma than in patients with a macroprolactinoma. Thus, what is wrong? Probably the absence of uniform classification of patients with presumed prolactinomas.
In the study by Pinzone et al. (1), inclusion criteria for "microprolactinomas" (n = 12) were a serum PRL level more than 15 ng/mL and either a normal computed tomography or magnetic resonance imaging scan of the pituitary or a tumor less than 1 cm in diameter. Obviously, this definition includes patients with idiopathic hyperprolactinemia. Although sexual dysfunction was present in all cases, testosterone levels were normal in 3 of 11 patients. In this setting, it has been recommended to rule out the presence of a biologically inactive macroprolactinemia (4). On the other hand, 4 of 11 patients remained testosterone deficient at follow-up despite normalization of PRL levels in at least 2 of them. The absence of restoration of gonadal function in men with small prolactinoma and mild testosterone deficiency is unusual (5), which suggests that PRL was not the cause of hypogonadism and should prompt the search for alternative diagnosis. Finally, it must be remembered that the finding of a "microadenoma" on scan in a patient with moderately elevated PRL levels may not always indicate the presence of a prolactinoma (6). Thus, the small group studied probably represents a highly heterogenous population. Nevertheless, normalization of PRL levels (<15 ng/mL) was achieved in 83% (10 of 12 patients). Moreover, it must be stressed that the two patients considered "DA resistant" had also nearly normal PRL values (between 15 and 17.5 ng/mL). Regarding macroprolactinomas, the study did not consider patients with tumors invading the cavernous sinuses separately, although a preliminary report indicates that invasive macroprolactinomas may be more frequently resistant to BRC than noninvasive ones (3). Highly aggressive macroprolactinomas often require multiple treatment modalities, but the authors excluded patients treated by surgery and/or adjunctive radiotherapy. Thus, the more aggressive macroprolactinomas should logically be searched for in the large group of patients (n = 77) excluded from the study.
In conclusion, the study by Pinzone et al. (1)
shows that PRL normalization is comparable in a group of male patients
with idiopathic hyperprolactinemia or presumed microprolactinoma and in
a selected group of patients with macroprolactinomas not requiring
surgery or radiation therapy. To facilitate comparison of treatment
results between centers, additional studies should refer to a precise
classification of prolactinomas. We propose such a classification in
Table 1
, which mainly relies on the following
evidences: microprolactinomas have a benign course and rarely progress
in size over time; invasion of the cavernous sinuses can be determined
by radiological criteria and is associated to higher proliferation
activity; DA-resistant prolactinomas have been shown to exhibit a more
severe clinical course both in human and in animal models; and combined
invasiveness and DA resistance usually does not allow normalization of
PRL levels, whatever the choice of therapy. The proposed classification
may also help the clinician to plan the treatment and inform about the
prognosis.
|
References
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Endocrinology | Endocrine Reviews | J. Clin. End. & Metab. |
| Molecular Endocrinology | Recent Prog. Horm. Res. | All Endocrine Journals |
