Inhibitory effect of calcium on serum prolactin.

The effect of calcium (Ca) infusions on serum prolactin (Prl) was studied in normal controls and children with disorders of Ca metabolism: Three patients with secondary hyperparathyroidism (vitamin D deficiency rickets), 2 children with idiopathic hypoparathyroidism, 13 epileptic patients with anticonvulsant drug induced inhibition of calcitonin (CT) secretion and 1 patient with vitamin D resistant rickets with normal CP and low PTH secretion. Ca induced a significant decline of serum Prl in most subjects which could not be explained by the associated increase of CT or decrease of iPTH. The important role of Ca for the in vitro secretion of dopamine has been established for a long time. It is speculated that the inhibitory effect of Ca infusion or serum Prl may be due to dopamine release from nerve tracts in the hypothalamus.