The specificity of serum prolactin as a diagnostic indicator of pituitary adenoma.

Serum prolactin levels were determined in 205 patients with a variety of intracranial diseases, including 70 cases with pituitary tumors. It is concluded that although the absence of elevated prolactin levels does not help to rule out pituitary pathology, the presence of hyperprolactinemia is highly specific for diseases of the pituitary and hypothalamus, and prolactin determination should be part of the regular work-up of pituitary tumor suspects. Excluding known causes of hyperprolactinemia, such as tranquilizing drug ingestion, the presence of neurological disease outside the hypothalamic-pituitary area was not associated with increased serum prolactin concentrations.