Effect of nifedipine on TRH stimulation of TSH and PRL release by the pituitary gland

Studies in vitro and in vivo have shown that thyrotropin-releasing hormone (TRH)-induced calcium ion changes in the adenohypophysial cells play an important role in release of hormones by the anterior pituitary. To determine the effect of the calcium blocker nifedipine on TRH-induced thyroid-stimulating hormone (TSH) and prolactin (PRL) release, TRH stimulation tests were performed before and after 74 hours of nifedipine therapy in ten patients. Although the magnitude of the TSH and PRL mean peak increase above baseline was slightly lower during calcium blocker administration (TSH 14.1 +/- 4.8 SEM v 16.4 +/- 4.5 SEM; PRL 37.7 +/- 4.5 SEM v 41.7 +/- 5.4 SEM), this was not statistically significant. Use of nifedipine in clinically effective doses does not appear to significantly interfere with TRH-stimulated release of TSH or PRL, in vivo.