The natural history of idiopathic hyperprolactinemia.

Idiopathic hyperprolactinemia (IH) can be defined as the presence of elevated serum PRL levels in a patient in the absence of demonstrable pituitary or central nervous system disease and of any other recognized cause of increased PRL secretion. This study examined the long term clinical outcome of 41 patients (mean age, 26 yr) with IH followed for up to 11 yr (mean, 5.5 yr). Initial and final PRL levels were determined by RIA in the same laboratory. A correction factor was used to obviate periodic changes in the potency of the NIH standards used in the PRL assay, so that all results are expressed in terms of the original VLS no. 1 standard. The initial serum PRL levels ranged from 27.2-243 ng/ml, with a mean of 57 ng/ml. Only three patients had initial serum PRL levels greater than 100 ng/ml. All had a normal skull x-ray and/or brain computed tomographic scan during their initial visit. All 41 patients had galactorrhea and/or amenorrhea. Serum PRL levels remained the same, decreased, or returned to normal in 34 of 41 patients. The mean PRL level at the time of reevaluation was 35 ng/ml. Thirty-four percent of the patients had a normal serum PRL level. Only 17% of the patients had serum PRL levels that were significantly higher (greater than 50% of their original value). Six of 9 patients with an initial serum PRL level less than 40 ng/ml had normal levels. One patient developed a pituitary tumor (initial PRL, 150 ng/ml). All patients reevaluated with brain computed tomographic scans had normal pituitary size. No patient reported a worsening of signs or symptoms, and in many, improvement (n = 16) or complete resolution (n = 8) of the amenorrhea and/or galactorrhea occurred. Twenty-seven spontaneous or bromocriptine-induced normal pregnancies and deliveries occurred without development of a pituitary tumor. Therefore, our data clearly challenge the use of ablative pituitary therapy for IH and raises questions of the benefit of chronic medical therapy for this condition.