Selenium

Definition

Selenium is a trace element that is essential for human health, playing a crucial role in the function of various enzymes and proteins, particularly those involved in antioxidant defense and thyroid hormone metabolism. Its significance extends to the regulation of thyroid hormones, which are vital for metabolic processes in the body. Selenium is incorporated into selenoproteins, which help protect cells from oxidative damage and support the conversion of inactive thyroid hormone (T4) to its active form (T3).

5 Must Know Facts For Your Next Test

1. Selenium is obtained through dietary sources, including Brazil nuts, seafood, meats, and whole grains, and is crucial for maintaining adequate levels in the body.
2. A deficiency in selenium can lead to various health issues, including impaired immune function and thyroid dysfunction, as it is essential for the production of selenoproteins.
3. Selenium's role in thyroid hormone metabolism includes facilitating the conversion of T4 into the more active T3 form, which is vital for metabolic regulation.
4. High levels of selenium can be toxic, leading to a condition known as selenosis, characterized by symptoms such as gastrointestinal distress, hair loss, and fatigue.
5. The recommended dietary allowance (RDA) for selenium varies by age and sex but generally ranges from 55 micrograms per day for adults.

Review Questions

• How does selenium influence thyroid hormone metabolism and what would be the consequences of its deficiency?
  • Selenium plays a key role in thyroid hormone metabolism by enabling the conversion of thyroxine (T4) into triiodothyronine (T3), the active form that regulates metabolic processes. A deficiency in selenium can lead to insufficient production of selenoproteins, resulting in impaired thyroid hormone activation. This may contribute to hypothyroidism and related symptoms such as fatigue, weight gain, and depression.
• Discuss the relationship between selenium and antioxidant defense mechanisms in the body.
  • Selenium contributes significantly to antioxidant defense mechanisms through its incorporation into selenoproteins, which function as antioxidants. These proteins help neutralize free radicals and prevent oxidative damage to cells. By reducing oxidative stress, selenium supports overall cellular health and protects against diseases associated with inflammation and aging.
• Evaluate how both deficiency and excess of selenium can impact metabolic health and thyroid function.
  • Both selenium deficiency and excess have profound effects on metabolic health and thyroid function. A deficiency can impair the synthesis of selenoproteins crucial for converting T4 to T3, leading to reduced metabolic rates and hypothyroid symptoms. Conversely, excessive selenium intake can result in toxicity or selenosis, causing symptoms that may mimic other health issues while also potentially disrupting normal thyroid hormone levels. Understanding this balance is vital for maintaining optimal health.

Related terms

Selenoproteins: Proteins that contain selenium in the form of the amino acid selenocysteine and are critical for various biological functions, including antioxidant defense and thyroid hormone metabolism.

Thyroid Hormones:

Hormones produced by the thyroid gland, mainly thyroxine (T4) and triiodothyronine (T3), that regulate metabolism, growth, and development in the body.

Antioxidants: Substances that inhibit oxidation and neutralize free radicals, thus protecting cells from oxidative damage, an important function enhanced by selenium.