Which of the following hormones are released directly by the thyroid gland?

• A. Parathyroid hormone (PTH)
• B. Calcitonin
• C. Thyroxine (T4)
• D. Cortisol

Answer: (C)

Verified step by step guidance

1. Understand the role of the thyroid gland: The thyroid gland is an endocrine gland located in the neck. It primarily produces hormones that regulate metabolism, growth, and development. The main hormones released by the thyroid gland are Thyroxine (T4), Triiodothyronine (T3), and Calcitonin.
2. Identify the hormones listed in the problem: The problem mentions Parathyroid hormone (PTH), Calcitonin, Thyroxine (T4), and Cortisol. We need to determine which of these are directly released by the thyroid gland.
3. Eliminate hormones not produced by the thyroid gland: Parathyroid hormone (PTH) is produced by the parathyroid glands, not the thyroid gland. Cortisol is produced by the adrenal glands, not the thyroid gland.
4. Confirm the hormones produced by the thyroid gland: Calcitonin is released by the parafollicular cells (C cells) of the thyroid gland and helps regulate calcium levels in the blood. Thyroxine (T4) is produced by the follicular cells of the thyroid gland and plays a key role in metabolism.
5. Conclude the correct answer: The hormones directly released by the thyroid gland are Calcitonin and Thyroxine (T4).