Lack of effect of chronic hypocalcaemia on serum prolactin response to chlorpromazine.

The effects of chronic hypocalcaemia on serum basal and chlorpromazine-stimulated prolactin (Prl) levels were studied in 16 patients with idiopathic or secondary hypoparathyroidism. These results were compared with the results of other chlorpromazine stimulation tests which were made in the normocalcaemic state after treatment with vitamin D, and in normal subjects. In hypocalcaemic and normocalcaemic states (mean serum Ca 5.8 +/- 0.24 mg/dl and 9.5 +/- 0.11 mg/dl, respectively) basal Prl levels were within the normal range and during stimulation the maximal stimulated levels in each state were not significantly different from each other. Also, the mean serum Prl levels obtained from a control group were not different from values in the normocalcaemic state. It is concluded that chronic hypocalcaemia does not inhibit Prl secretion and low serum parathyroid hormone levels do not affect basal and chlorpromazine-stimulated Prl secretion.