In Thyrotoxicosis, B-blockers do not control -

Beta blockers ameliorate the symptoms of hypehyroidism that are caused by increased beta-adrenergic tone. These include palpitations, tachycardia, tremulousness, anxiety, and heat intolerance. n many tissues, hypehyroidism is associated with an increased number of beta-adrenergic receptors . The ensuing increase in beta-adrenergic activity is responsible for many of the symptoms associated with this disorder. It also explains the ability of beta blockers to ameliorate rapidly many of the symptoms, including palpitations, tachycardia, tremulousness, anxiety, and heat intolerance. Ref - pubmed.com