**Question:** In Thyrotoxicosis, β-blockers do not control-

A. Hyperthyroidism
B. Tachycardia
C. Hypermetabolism
D. Agitation and anxiety

**Core Concept:**
Thyrotoxicosis refers to a state of increased thyroid hormone production or action, leading to symptoms and signs related to high thyroid hormone levels. β-blockers are medications that block the effects of catecholamines on β-adrenergic receptors, which are involved in regulating heart rate, blood pressure, and other physiological processes.

**Why the Correct Answer is Right:**
In thyrotoxicosis, the increased thyroid hormone levels primarily affect the autonomic nervous system by stimulating the β1 receptors, leading to tachycardia (rapid heart rate) and other cardiovascular manifestations. β-blockers primarily target the cardiovascular system by blocking β1 receptors, but they do not address the underlying hyperthyroidism and its effects on other systems, such as the musculoskeletal system, nervous system, and gastrointestinal system.

**Why Each Wrong Option is Incorrect:**
A. Hyperthyroidism: While β-blockers may not control the primary cause of hyperthyroidism, they can be used as supportive therapy to manage symptoms like hypertension and arrhythmias associated with thyrotoxicosis.
B. Tachycardia: As explained above, β-blockers primarily target the cardiovascular system, and they can control tachycardia caused by excessive thyroid hormone effects on β1 receptors.
C. Hypermetabolism: β-blockers do not address the increased thyroid hormone production or action causing hypermetabolism. They primarily intervene in cardiovascular manifestations.
D. Anxiety and agitation: β-blockers can help manage these symptoms due to their cardiovascular effects but do not address the cause of anxiety, which may be unrelated to thyrotoxicosis.

**Clinical Pearl:**
In thyrotoxicosis, the appropriate treatment regimen includes antithyroid drugs (e.g., methimazole or propylthiouracil) to target the primary cause of hyperthyroidism and manage symptoms effectively. In some cases, β-blockers can be used in conjunction with antithyroid drugs to manage symptoms like hypertension, palpitations, and arrhythmias.

In summary, β-blockers primarily focus on managing cardiovascular manifestations of thyrotoxicosis, while addressing the cause of thyrotoxicosis (hyperthyroidism) is crucial for comprehensive management.