Final answer:
Iodine (I) is the element necessary for the proper function of the thyroid gland. It is vital for the production of thyroid hormones and is added to table salt to prevent deficiencies. Other elements like sodium and potassium are important for health but not directly involved in thyroid function.
Step-by-step explanation:
The element required for the proper function of the thyroid gland from the provided list is iodine (I), which is an essential trace element for the human body. Iodine is critical for the synthesis of thyroid hormones, which regulate many essential biological processes, including metabolism, growth, and development. Without adequate iodine intake, thyroid function is impaired, leading to conditions such as goiter, hypothyroidism, and developmental issues.
To prevent iodine deficiency, table salt is often iodized. This tactic has significantly reduced the prevalence of iodine deficiency and associated health issues in many parts of the world. However, in areas where iodine intake is still insufficient, health problems related to thyroid malfunction remain a risk.
While other elements mentioned, such as sodium (Na) and potassium (K), are also important for overall health, they do not play a direct role in thyroid function like iodine does.