Calcium ion and pituitary hormones: effect of calcium channel blockers on stimulated secretion of pituitary hormones.

The effects of two calcium channel blockers nifedipine (20 mg sublingual), and verapamil (10 mg i.v.) on growth hormone (GH), thyrotropin (TSH), prolactin (PRL) and gonadotropin (LH and FSH) secretion induced by growth hormone releasing hormone (GHRH), hypoglycemia, thyrotropin releasing hormone (TRH), metoclopramide and gonadotropin releasing hormone (GnRH), were studied in a group of normal volunteers (27 men and 8 women). Neither nifedipine nor verapamil had any effect on PRL, TSH or gonadotropin release. Verapamil did not cause variations in GH secretion following GHRH and insulin-induced hypoglycemia, whereas nifedipine significantly reduced the elevation in GH induced by GHRH; however the GHRH-mediated GH rise still remained within the normal range in all subjects. Our results suggest that neither nifedipine nor verapamil have important effects on stimulated pituitary hormone secretion, at least under conditions of acute administration.