Oxygen Consumption in Patients with Hyperthyroidism Before and After Treatment With &bgr;-Blockade Versus Thyrostatic Treatment: A Prospective Randomized Study

ObjectiveTo evaluate randomly the effect of thyrostatic treatment (tiamazole) versus selective (metoprolol) and nonselective &bgr;-blockade (propranolol) on whole-body energy metabolism in women with hyperthyroidism. Summary Background Data&bgr;-blockade is used as an alternative to thyrostatic drugs in the preoperative treatment of patients with hyperthyroidism. &bgr;-blockers have well-established symptomatic effects, but in contrast to antithyroid drugs &bgr;-blockade is thought to lack direct effects on the increased metabolism in hyperthyroidism. MethodsWhole-body oxygen consumption and carbon dioxide production was measured in a semiopen canopy system with paramagnetic O2 and infrared CO2 sensors. A constant flow generator and the gas-dilution method for calculation of gas flow were used. Anabolic parameters were body weight, triceps skinfold, and arm muscle circumference. ResultsTiamazole normalized oxygen consumption and induced signs of anabolism with improved nutritional state. Metroprolol did not affect oxygen consumption. Propranolol reduced elevated oxygen consumption by 54%. Body weight and other anthropometric assessments were stable after specific and nonspecific &bgr;-blockade, which also led to symptomatic relief in approximately 90% of the patients. ConclusionTiamazole was the most effective drug to oppose the adverse effects of hyperthyroidism. Therefore, thyrostatic agents are recommended for preoperative treatments of patients with severe catabolic hyperthyroidism. Whenever &bgr;-blockers are chosen for treatment of hyperthyroidism, propranolol (&bgr;1 + &bgr;2) has an advantage because it reduces the metabolic rate, whereas selective &bgr;1-blockade seemed to provide only symptomatic relief, related to the normalization of heart rate.