Is selenium safe and effective for Hashimoto’s thyroiditis? Original paper

In this meta-analysis, selenium supplementation improved levels of thyroid-stimulating hormone and thyroid peroxidase antibodies in participants with Hashimoto’s thyroiditis.

The effect of supplementation with selenium on outcomes related to Hashimoto’s disease.

The primary outcome was thyroid-stimulating hormone (TSH) levels in participants who were not on thyroid hormone replacement therapy (THRT; THRT affects TSH levels), though analyses were also performed in participants who were on THRT and in participants overall.

The secondary outcomes were total and free T4, total and free T3, thyroid antibodies (thyroid peroxidase antibodies, thyroglobulin antibodies, and thyrotropin receptor antibodies), thyroid ultrasound findings (opaqueness and thyroid volume), immune and oxidative biomarkers (e.g., malondialdehyde), participant-reported outcomes, and adverse events.

A total of 2,274 participants, of whom 120 were children or adolescents.

Additionally, 227 of the participants were pregnant.

In this meta-analysis of 32 randomized controlled trials, the study participants were given dosages of selenium of 80 to 400 µg (micrograms) per day for 2 to 12 months. In the control groups, the participants took a placebo or nothing.

Eighteen studies assessed serum selenium levels at baseline. The participants in 9 and 7 studies were severely and mildly deficient in selenium, respectively. The participants in 2 studies had sufficient selenium levels.

Nineteen studies were conducted in Europe, 11 studies in Asia, 4 studies in the Middle East, and 1 study in South America.

Selenium supplementation improved TSH levels in participants who were not on THRT, compared to the control participants (small effect size; moderate quality of evidence).

Additionally, selenium supplementation improved (decreased) thyroglobulin antibodies in participants who were not on THRT (effect size not accessible). Furthermore, selenium improved (decreased) thyroid peroxidase antibodies and malondialdehyde levels (large effect sizes) in the participants overall. The quality of evidence was rated as low for thyroglobulin antibodies and thyroid peroxidase antibodies and was not rated for malondialdehyde.

Adverse effects were no different in the selenium group compared to the control group (moderate quality of evidence).

THRT typically causes low TSH levels, such that selenium supplementation is unlikely to affect these levels. However, THRT does not affect antibody levels.

The upper end of TSH reference ranges were mostly less than or equal to 4 milli-IUs per liter.

The researchers did not measure dietary intake of selenium, which would have likely differed over the different geographies studied.