Effect of Ca++ chaxrnel blocking agents on experimental hyperthyroidi in the dog

This work was designed to study the effect of Ca++ channel blockers [verapamil and nifedipine] on hormonal release and actions in hyperthyroidistn. In hyperthyroid crisis, intravenous verapamil decreased serum tniodothyronine [T[3]], blood pressure, heart rate and double product cardiac output index and succeeded to reduce the encountered supraventnicular and ventricular arrhythmias. Nifedipine decreased the blood pressure and double product index, yet it did not induce any significant effect on thyroid honones or blood lipids. In chronic hyperthyroidiam, verapamil increased serum lipids and controlled nearly all cardiovascular complications of the disease. Nifedipine increased both serum triiodothyronine and tetraiodothyronine [Thyroxine, T[4]], as yell as free fatty acids [FFA]. It controlled hyperthyroid hypertension, but failed to control the rest of the existing cardiovascular ccniplications

Effects of Ca++ channel blocking agents on pituitary thyroid hormones, serum lipids and cardiovascular functions in euthyroid dogs

The effect of verapamil and mifedipine was studied in euthyroid dogs to detect whether these drugs alter pituitary-thyroid output and/or actions. Verapamil induced a significant decrease of serum TSH, T[3] and T[4] as well as significant increase of serum lipids. It also exhibited a bradycardiac action. Nifedipine decreased only serum T[3] and induced a significant increase in serum FFA and total cholesterol. It also led to a decrease in diastolic pressure and an increase in heart rate