How does endocrine gland function affect the body after removal?

The correct choice highlights that the removal of an endocrine gland significantly impacts body metabolism. Endocrine glands regulate various hormones that are crucial for maintaining metabolic processes, including those that control how the body utilizes energy from food and how it manages weight. For instance, the thyroid gland produces hormones that regulate the body's metabolic rate, affecting energy expenditure, weight management, and overall metabolic homeostasis. When such a gland is removed, the disruption in hormone levels can lead to metabolic imbalances, resulting in symptoms like weight gain or loss, fatigue, and other metabolic-related issues.

The other options do not address the primary role of endocrine glands as comprehensively as metabolism does. While heart rate may be affected due to hormonal changes, and muscle growth may be influenced by certain hormones, the most direct and critical impact of endocrine gland removal is on metabolism, which encompasses these processes as a whole. Immune response can also be influenced by hormones, but again, the central focus remains on how metabolic processes are fundamentally altered post-removal.