REVIEW: PITUITARY PROLACTINOMAS*
Authors: NABARRO J. D. N. 
Published: March 2008

A distinction is made between large and small prolactinomas. They have different presenting symptoms, sex distribution and natural history. From a series of 263 patients with obviously enlarged pituitary fossae on lateral skull x‐ray, seventy‐four were identified as having chromophobe adenomas and thirty‐four of these are believed to have prolactinomas (46%). It is pointed out that an enlarged pituitary fossa is not necessarily due to a pituitary tumour. Levels of prolactin are given for patients with craniopharyngiomas, hypothalamic disorders, Cushing's syndrome, Nelson's syndrome and acromegaly. It is emphasized that a modestly elevated prolactin level with an enlarged pituitary fossa does not mean that the patient has a prolactinoma, the hyperprolactinaemia may be due to interference with the hypothalamic prolactin inhibiting mechanism. The special problems of acromegaly are discussed.

The thirty‐four large prolactinomas diagnosed before treatment were supplemented by fourteen more cases diagnosed on prolactin measurements made after the initial operation. In addition to forty‐eight large prolactinomas, 103 small prolactinomas were identified. Only thirty‐six of the latter were treated surgically, the diagnosis in the other sixty‐seven cases being presumptive. The presenting symptoms and sex incidence are reviewed.

Review of the forty‐eight cases of large prolactinoma shows that it may be an unpleasant invasive tumour. Treatment by transfrontal or transphenoidal surgery may occasionally result in a cure but the results are disappointing. X‐ray therapy is relatively ineffective. Bromocriptine may produce dramatic response but occasional cases are relatively resistant to its action. The value of serial prolactin measurements to monitor tumour growth is stressed.

In relation to the small prolactinomas, a number of questions are considered. It seems likely that in the sixty‐seven patients not explored surgically, the majority had microadenomas. The results of transsphenoidal surgery in thirty‐six patients with higher prolactin levels are reported (twenty cured by surgery alone, two rendered panhypopituitary). The natural history of the small prolactinoma is discussed, the reported incidence of small prolactinomas at autopsy is noted, seven patients followed for from 3 to 6 years showed no change in the prolactin level. The advice to be given to a patient with a small prolactinoma who wishes to get pregnant is reviewed. It is suggested that special care should be exercised if the prolactin level exceeds 4000 mU/1. The floor of the pituitary fossa should be scrutinized on tomograms and the upper limit by computerized tomography. If close observation of the patient is possible through pregnancy, bromocriptine may be given to restore ovulation. If the prolactin level rises excessively or a visual field defect occurs, bromocriptine should be restarted at once.

The effect of x‐ray therapy on prolactin levels in fifteen patients (14 after surgery) is reported. High prolactin levels are little changed, four patients with lower initial levels (< 7000 mU/1) achieved normoprolactinaemia in 2–6 years.