Abstract
By a systematic review and meta-analysis to investigate clinically relevant effects of selenium supplementation in patients with chronic autoimmune thyroiditis. Controlled trials in adults (≥18 years) with autoimmune thyroiditis, comparing selenium with or without levothyroxine substitution, versus placebo and/or levothyroxine substitution, were eligible for inclusion. Identified outcomes were serum thyrotropin (thyroid stimulating hormone) levels in LT4-untreated patients, thyroid ultrasound and health-related quality of life. Eleven publications, covering nine controlled trials, were included in the systematic review. Random effects model meta-analyses were performed in weighted mean difference for thyroid stimulating hormone, ultrasound and health-related quality of life. Quality of evidence was assessed per outcome, using GRADE. Meta-analyses showed no change in thyroid stimulating hormone, or improvements in health-related quality of life or thyroid echogenicity (ultrasound), between levothyroxine substitution-untreated patients assigned to selenium supplementation or placebo. Three trials found some improvement in wellbeing in patients receiving levothyroxine substitution, but could not be synthesized in a meta-analysis. The quality of evidence ranged from very low to low for thyroid stimulating hormone as well as ultrasound outcomes, and low to moderate for health-related quality of life, and was generally downgraded due to small sample sizes. We found no effect of selenium supplementation on thyroid stimulating hormone, health-related quality of life or thyroid ultrasound, in levothyroxine substitution-untreated individuals, and sporadic evaluation of clinically relevant outcomes in levothyroxine substitution-treated patients. Future well-powered RCTs, evaluating e.g. disease progression or health-related quality of life, are warranted before determining the relevance of selenium supplementation in autoimmune thyroiditis.
Highlights
Chronic autoimmune (AIT) or Hashimoto’s thyroiditis affects 1–2 % of the population with increasing prevalence with age and a female preponderance
We found no effect of selenium supplementation on thyroid stimulating hormone, healthrelated quality of life or thyroid ultrasound, in levothyroxine substitution-untreated individuals, and sporadic evaluation of clinically relevant outcomes in levothyroxine substitution-treated patients
Where data was presented as median with interquartile range (IQR), the median was used as a mean and a standard deviations (SD) was calculated by the formula IQR/1.35 [15]
Summary
Chronic autoimmune (AIT) or Hashimoto’s thyroiditis affects 1–2 % of the population with increasing prevalence with age and a female preponderance. In communities replete in iodine intake, it is the predominant cause of hypothyroidism [1, 2]. The etiology is multifactorial and based on genetic susceptibility in a complex interaction with numerous environmental triggers [3, 4], possibly including selenium deficiency [5]. The standard treatment is life-long levothyroxine substitution (LT4) to normalize circulating thyrotropin [thyroid stimulating hormone (TSH)] levels. Recent insights suggest that LT4 cannot ensure a euthyroid state in all tissues simultaneously [6], and a place for selenium supplementation in the treatment of AIT has been much debated [7]. Selenium is an essential micronutrient with a wide range of effects in, e.g
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