Final answer:
The largest endocrine gland in the human body is the thyroid gland, which is situated in the neck and regulates the body's metabolism.
Step-by-step explanation:
The largest endocrine gland in the human body is the thyroid gland. Located in the neck, this gland plays a crucial role in regulating metabolism by producing thyroid hormones that control how cells use energy and make proteins. The pituitary gland, while often referred to as the 'master gland' due to its role in controlling other endocrine glands, is actually much smaller in size. The pancreas and thymus gland are also part of the endocrine system, but they do not surpass the thyroid in size. Therefore, the correct answer is A. Thyroid gland.
The pituitary gland is the largest endocrine gland.