Introduction
Hyperthyroidism, Hyperthyroid, hyperthyroidism, hyperthyroid, weight loss
PRIMARY HYPERTHYROIDISM, HYPERTHYROIDISM, ENDOCRINE DISORDER, HEAT INTOLERANCE, HYPERTHYROID, HYPERTHYROIDISM, HYPERTHYROID, HEAT, COLD, HYPERTHYROID SYMPTOMS, BROWN
Hyperthyroidism is a common endocrine disorder, which is characterized by an excessive synthesis and release of thyroid hormones (TH). Hyperthyroid patients often suffer from weight loss and heat intolerance due to higher resting energy expenditure (REE) (The SNS and its main transmitter norepinephrine activate brown adipose tissue (BAT). BAT is a thermogenic tissue which is usually activated in response to cold exposure in order to maintain the normal body core temperature. It can convert chemical energy from triglycerides or glucose directly into heat. Brown adipocytes contain a large number of mitochondria and store lipids in small intracellular droplets as opposed to the large single lipid drop found in white adipocytes.The importance of TH for the function and differentiation of brown adipocytes is underscored by the fact that BAT expresses high levels of deiodinase 2 (DIO2) which converts thyroxin (T4) to triiodothyronine (T3) (Medical treatment of hyperthyroidism aims to reduce TH synthesis and to lower plasma TH levels using antithyroid drugs such as methimazole. However, β-adrenoreceptor (β-AR) antagonists (β-blockers) are often administered to rapidly control hyperthyroid symptoms. Especially the non-selective β-blocker propranolol is widely used and is considered the drug of choice (We hypothesized that propranolol might immediately decrease REE in patients suffering from primary hyperthyroidism by reducing BAT activity. We investigated the effect of a single dose of 80 mg of propranolol on REE in hyperthyroid patients.