Endocrine Abstracts

Introduction

Prolactinomas are the most common hormone-secreting pituitary tumours encountered in the clinic. They are usually treated with dopamine agonists (DA): bromocriptine (BRC) and cabergoline (CAB), which are highly effective in the majority of cases. DA resistance is the failure to achieve normal levels of prolactin and, or reduction of the adenoma with at least 50%.

Aim

to assess the prevalence of the known factors that contribute to DA resistance (male gender, younger age at diagnosis, large tumours, the invasiveness of the tumour) among patients that do not respond to medical treatment.

Materials and methods

222 patients with prolactinoma were retrospectively assessed for treatment responsiveness. Gender, age of the diagnosis, serum prolactin levels, the dimensions of the pituitary adenoma were compared in responsive and resistant patients. Prolactin was measured by chemiluminescence and tumour volume and extension by computed tomography scan or MRI.

Results

there were 188 patients responsive to DA therapy and 34 resistant ones. There is no significant gender differences between the 2 groups (M:F = 83:105 in responsive group vs. 16:18 in resistant group, n = ns, chi square test). Resistant patients tend to be younger (30.5 ± 12.5 years) than responsive ones (35.6 ± 13.6 years), P = ns. Serum median prolactin was similar in responsive patients (650 ng/ml) and in resistant ones (462 ng/ml). Median maximum diameter was also similar (2.1 cm vs.2.12 cm).

Conclusions

In our series, there were no significant differences regarding gender, age at diagnosis, initial prolactin levels or tumour volume between patients responsive or resistant to DA therapy. Attention should be payed to histological and genetic differences between these patients.