Which description best matches the normal anatomical position of the thyroid gland?

In the hypothalamic-pituitary-thyroid axis, elevated circulating thyroid hormones suppress the release of TRH and TSH. What is the main physiological purpose of this feedback mechanism?

In a patient with normal thyroid function, much of the circulating thyroxine (T4) is converted into a more potent hormone in target tissues. Which statement best describes this conversion?

Researchers place young tadpoles in water containing a low concentration of thyroxine. Compared with untreated tadpoles of the same age, the treated group develops hind limbs and loses their tails earlier. Which conclusion is best supported by these observations?

A newborn screening program identifies an infant with congenital hypothyroidism. If treatment is not started promptly, which long-term outcome is most likely to occur?