Endocrine Abstracts

Background: Pituitary stalk compression by sellar/parasellar tumours [commonly non-functioning pituitary adenomas (NFA) or craniopharyngiomas (CR)] is one of the causes of hyperprolactinaemia. However, in such cases the upper limits of serum prolactin (PRL) are not clearly defined ('grey zone': 3000-6000 mU/L) causing confusion in the differential diagnosis between disconnection hyperprolactinaemia and prolactin-secreting adenomas.

Objective: To investigate the range of PRL values at presentation in patients with NFA or CR.

Methods: All the patients who presented to our Department between 1/1998 and 6/2003 with NFA and between 1990-2003 with CR were studied (histologically confirmed).

Results: Sixty patients with NFA [median age 56 (range 27-83) years, 37 males] and 34 with CR [median age 46 (range 16-83) years, 24 males] were identified. Median PRL values were 391 mU/L (range 22-2229) in NFAs and 440 mU/L (range 12-2902) in CRs. 84% of both groups had PRL < 1000 mU/L, 13% between 1000-2000 and 3% between 2000-3000. Manifestations of hypogonadism were present in 27% of NFAs and 50% of CRs and galactorrhoea in 3% of NFAs and 6% of CRs. One subject within the NFA group presented as apoplexy, while the remaining ones were all diagnosed with macroadenomas. All the CRs had an extrasellar component. There was no difference in the PRL levels between NFAs and CRs. Females had higher PRL values than males (median 746 vs 336 mU/L, p<0.01). There was a negative correlation between PRL values and age at presentation (r=-0.22, p=0.03).

Conclusion: In the vast majority of cases (97%) disconnection hyperprolactinaemia due to NFAs or CRs presents with serum PRL values < 2000 mU/L. In contrast to earlier studies, levels > 3000 mU/L in the presence of a tumour in the pituitary area are unlikely to be associated with disconnection hyperprolactinaemia and therefore, prolactinoma pathology should be considered.