The correct answer is A. Thyroxin.
Thyroxin is a hormone produced by the thyroid gland. It is responsible for regulating metabolism, growth, and development. Thyroxin is also important for maintaining a healthy heart rate and blood pressure.
Calcitonin is a hormone produced by the parathyroid glands. It helps to regulate blood calcium levels by promoting the absorption of calcium from the intestines and the deposition of calcium in bones.
Insulin is a hormone produced by the pancreas. It helps to regulate blood sugar levels by promoting the uptake of glucose from the bloodstream into cells.
Adrenaline is a hormone produced by the adrenal glands. It is released in response to stress and helps to prepare the body for the “fight or flight” response.
The thyroid gland is often referred to as the “pacemaker of the endocrine system” because it produces hormones that regulate the activity of other endocrine glands.