Thyroid Health

What does an underactive thyroid feel like?

Too little thyroid hormone can cause fatigue, constipation, dry skin, and sensitivity to cold. These symptoms have other possible causes, so diagnosis uses blood tests rather than symptoms alone. 1

Is an underactive thyroid always an iodine problem?

No. IQWiG identifies chronic thyroid inflammation, including Hashimoto’s disease, as the most common cause. Severe iodine deficiency, thyroid surgery, and some medicines are other possibilities. 1

Can excess iodine make things worse?

A review describes both underactive and overactive thyroid disorders after excess iodine exposure. People with existing thyroid disease can be especially susceptible. Seaweed and iodine-containing supplements are among the potential sources. 2

Where do iodine and selenium fit?

These nutrients have different roles, and the reason for supplementation matters. 3 4

IodineSupported

Iodine is needed to make thyroid hormones. Correcting inadequate intake addresses a real nutritional need; this does not make extra iodine a general treatment for thyroid disease. 2 3

SeleniumMixed

Some trials in autoimmune thyroiditis lowered thyroid antibodies, while others found no improvement in thyroid function or quality of life. An antibody change alone does not demonstrate that someone feels better. 4

KelpToo little evidence

Iodine content varies, and a review found discrepancies between labels and measurements in kelp-containing prenatal supplements. It recommends avoiding kelp supplements in favor of more predictable iodine preparations when supplementation is appropriate. 2

What helps a confirmed underactive thyroid?

Thyroid hormone tablets can replace the missing hormone and usually relieve symptoms. Nutrient research should be read alongside this established treatment, rather than used to infer that a supplement can replace it. 1

Does pregnancy change the discussion?

Iodine needs increase during pregnancy, but excessive intake can also harm thyroid function. Selenium is a separate question: the American Thyroid Association advises against supplementation in pregnant women with thyroid autoimmunity. 2 3 4

Which supplements are not reviewed here?

This page does not assess guggul, tyrosine, coleus, zinc, sea moss, or bladderwrack as thyroid treatments.

Questions people ask