The rationale for selenium supplementation in patients with autoimmune thyroiditis, according to the current state of knowledge

Abstract

Selenium (Se) supplements are commonly prescribed to autoimmune thyroiditis (AIT) patients by European endocrinologists, despite the lack of official guidelines. The majority of Europe is depleted of natural Se sources, and the daily population intake does not comply with recommended values. Optimal individual plasma Se concentration is reached when the selenoproteins (selenoprotein P, glutathione peroxidase) are fully saturated. However, Se intake has to be regulated because both Se shortage and overdose negatively impact health. In the case of AIT, Se may alleviate symptoms or prevent progression to hypothyroidism and postpartum hypothyroidism. Se supplementation in euthyroid, subclinical, or overt hypothyroid AIT patients decreased thyroid autoantibodies, lowered or maintained the TSH level, decreased the fT4/fT3 ratio, reduced the body's oxidative stress and inflammatory status, and amended quality of life and thyroid ultrasound structure and volume. In pregnant females, adequate Se intake protected them against miscarriages, preeclampsia/hypertension, preterm birth, small-for-gestational-age infants' birth, and improved child's neuropsychological development. In the elderly population, adequate Se supplementation decreased cardiovascular diseases and hypertension risk, but prolonged intake of excessive doses increased the all-cause mortality rate. Routine Se supplementation implementation requires from researchers and clinicians consideration of specific populational differences in natural Se and iodine supply, the patient's clinical situation (supplementation simultaneously or before levothyroxine treatment, AIT/non-AIT hypothyroidism), individual response to supplementation (Se and selenoprotein P assessment), predisposition (genetic testing), the status of other trace elements, and the interplay between those micronutrients. Moreover, the safety of commercially available Se formulations, doses, and duration of treatment should be determined. Proper guidelines are warranted to standardise the medical approach to Se supplementation. This article presents a comprehensive review of recent randomised-controlled trials, meta-analyses, and clinical trials concerning the risks and benefits of Se supplementation in different clinical settings and specific populations with particular emphasis on AIT in a practical manner. (Endokrynol Pol 2021; 72 (2): 153-162)

Natural Autoimmunity to Selenoprotein P Impairs Selenium Transport in Hashimoto’s Thyroiditis

“…In general, the pathogenesis of AITD is a multifaceted process, where the essential production of hydrogen peroxide needed for thyroid hormone biosynthesis may contribute to tissue inflammation, gland destruction, and the generation of novel autoantigens [ 7 , 8 ]. Accordingly, anti-inflammatory and antioxidative measures are considered in prevention and treatment of AITD [ 9 , 10 ]. Observational studies have indicated an inverse relationship between the intake of the essential trace element Se with thyroid volume [ 11 ], the development of thyroid nodules [ 12 ] and thyroid disease [ 13 ].…”

Dietary supplements in hypothyroidism [pdf]

“…Socha et al (2012) found that even though the average content of Se in serum of the patients with Hashimoto's disease was significantly lower than healthy subjects, dietary habits had a minor influence on the Se levels in these patients. On the other hand, Se supplementation can reduce serum thyroid peroxidase levels in patients with autoimmune thyroiditis with LT4 treatment (Wichman et al, 2016) or lower or maintain the TSH level in an untreated population decrease the fT4/fT3 ratio (Filipowicz et al, 2021). According to Pirola et al (2020) supplementation with selenomethionine is associated with normalization of serum TSH levels that is maintained 6 months after selenium withdrawal in 50% of patients with subclinical hypothyroidism due to chronic autoimmune thyroiditis.…”

“…Despite the lack of official guidelines, European endocrinologists commonly prescribe Se supplements to autoimmune thyroiditis patients. However, proper guidelines on Se supplementation are needed (Filipowicz et al, 2021).…”

The impact of levothyroxine on thyroid autoimmunity and hypothalamic–pituitary–thyroid axis activity in men with autoimmune hypothyroidism and early-onset androgenetic alopecia

“…The study design did not allow us to totally eliminate the "regression toward the mean" effect, arising when an extreme variable on the first measurement is closer to the average on subsequent measurements [27]. Furthermore, the study population was characterized by sufficient iodine [28] and low selenium [29,30] intake. It is not certain whether the impact of levothyroxine treatment is similar in patients inhabiting iodine-deficient and seleniumsufficient areas.…”