Selenium

What it is

Selenium is an essential trace mineral built into selenoproteins, including glutathione peroxidases and the deiodinase enzymes that convert thyroid hormone to its active form. This is why it is used both to correct dietary deficiency and as an adjunct in hypothyroidism, particularly autoimmune thyroid disease. It supports thyroid enzyme function rather than replacing thyroid hormone.

Used for

• Deficiency
• Hypothyroidism

What to know while taking it

It is taken with food, which is gentler on the stomach and matches how selenium is normally absorbed from the diet. The safety window between an adequate intake and an excessive one is unusually narrow for a mineral, so stacking several supplements or fortified products that each contain selenium is the main way people overshoot. TPO antibodies and TSH are the markers followed during use, since the point of supplementing in thyroid disease is to see whether those values move.

When to see a doctor

A garlic-like smell on the breath, metallic taste, hair or nail loss, or unexplained nausea can indicate too much selenium and should be assessed by a doctor. New palpitations, weight change or fatigue suggest thyroid values need rechecking.

Worth knowing

• Narrow safety window

Markers to watch

• TPO antibodies
• TSH