Optometry Admission Test (OAT) Practice

Which gland produces both T4 and T3 hormones?

1. The adrenal gland

2. The hypothalamus

3. The thyroid gland

4. The parathyroid gland

The correct answer is: The thyroid gland

The thyroid gland is responsible for producing both thyroxine (T4) and triiodothyronine (T3) hormones. These hormones play a crucial role in regulating metabolism, growth, and development in the body. The synthesis of T4 and T3 occurs through the uptake of iodine from the diet, which is essential for their production. The gland itself is located in the neck and is butterfly-shaped, straddling the trachea. T4 is primarily released into the bloodstream and serves as a prohormone, with T3 being the more active form that influences metabolic processes. The balance and secretion of these hormones are also regulated by thyroid-stimulating hormone (TSH) produced by the pituitary gland, which highlights the interconnectedness of the endocrine system. The other glands mentioned in the choices, such as the adrenal gland, hypothalamus, and parathyroid gland, have different functions. The adrenal gland is involved in producing hormones related to stress response, the hypothalamus regulates bodily functions through hormone secretion but does not produce T3 or T4, and the parathyroid gland is primarily responsible for regulating calcium levels in the blood. Understanding the specific roles of these glands clarifies why the thyroid gland