Lack of Effect of Verapamil on Diurnal and Thyrotropin Releasing Hormone Stimulated Thyrotropin Levels in Man

We have evaluated the effects of oral administration of the calcium blocker verapamil on the pituitary secretion of TSH. Verapamil was administered 120 mg tid to 6 healthy volunteers. Plasma TSH was measured with an ultrasensitive immunoradiometric assay. TSH secretion was assessed by a 24-hour profile of unstimulated plasma concentrations and by the effect of TRH stimulation before and after 7 days of verapamil administration. No effects of verapamil was found on either basal or stimulated secretion of TSH.