Which hormones does the thyroid release and what are their functions?

• A. Triiodothyronine (T3) and thyroxine (T4) regulate metabolism, digestion, muscle control, and calcium levels.
• B. Insulin and glucagon regulate blood glucose.
• C. Parathyroid hormone and calcitonin regulate calcium.
• D. Adrenaline and noradrenaline regulate sympathetic activity.

Answer: (A)

Thyroid hormones are triiodothyronine (T3) and thyroxine (T4). Their main job is to set the body's metabolic rate and influence how every tissue uses energy. They ramp up cellular metabolism, increase heat production, and support growth, development, and normal function of many organs. This broad metabolic control touches digestion, as gut enzymes and motility are affected, and it also influences how muscles work and how energy is used.

Calcium regulation, while connected to overall body metabolism, is controlled mainly by parathyroid hormone and calcitonin, not directly by thyroid hormones. Thyroid hormones can affect bone turnover and calcium handling indirectly, but the primary calcium-keeping roles belong to the parathyroids and calcitonin.

So the statement that the thyroid releases T3 and T4 and that these hormones regulate metabolism, digestion, muscle activity, and related systemic functions best captures the thyroid’s hormonal role. The other options point to hormones from other glands (pancreas or adrenal glands) or to calcium hormones that are not the thyroid’s main products.