Levodopa Suppression of Prolactin in Nonpuerperal Galactorrhea

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Abstract
Nonpuerperal lactation may be the result of pituitary tumors or functional pituitary disorders. Elevations of serum prolactin measured by radioimmunoassay were found in three patients with pituitary tumors and in one of two patients with functional pituitary disorders. Ingestion of 0.5 g of levodopa (L-dopa) produced a profound fall in serum prolactin in all patients by 90 minutes; thereafter, levels tended to rise toward base-line values. Sustained suppression of serum prolactin levels could not be achieved when L-dopa was given four times daily, although the suppressive effect of a single dose was always demonstrable. More prolonged treatment of one patient did not decrease lactation or lower basal prolactin levels.Because L-dopa probably exerts its effects on the pituitary gland via the hypothalamus, these studies suggest that pituitary tumors associated with lactation may not be autonomous.