More information about text formats
We are thankful for the enriching comments on our article on the selenium (Se) insufficiency cut-off point value related to severe Graves’ orbitopathy (GO).
We concur that the area under the ROC curve revealed an imperfect differentiation between mild and severe GO. Since GO is a multifactorial disease, a single trace element like selenium should be combined with other determinants in clinical practice. Nonetheless, finding from our study built upon the existing evidence on the association between selenium and GO by proposing a possible cut-off-point that should be further validated with a larger and/or different population. Also, future studies that include healthy individuals without orbitopathy will generate more obvious comparative evidence on the effects of Se on the disease course.
Universal normal ranges of serum selenium (Se) levels have not been set because of the geographical variability in selenium levels. The ‘sufficient’ levels of serum selenium have been relative to clinical parameters, e.g., prevention of Keshan disease at > 21 mcg/l, the optimal activity of IDIs (iodothyronine 5’ deiodinase) at > 65 mcg/l (1). The cut-point identified in our study was compatible with at least three studies (90mcg/l, 95mcg/l, and 89 mcg/l) regarding plasma selenium needed to achieve the full expression of plasma GPx (glutathione peroxidase) (1-3).
1. Thomson CD. Assessment of requirements for selenium and adequ...
1. Thomson CD. Assessment of requirements for selenium and adequacy of selenium status: a review. Eur J Clin Nutr 2004;58:391-402.
2. Duffield AJ, Thomson CD, Hill KE, et al. An estimation of selenium requirements for new Zealanders. Am J Clin Nutr 1999;70:896-903.
3. Thaomson CD, Robinson MF, Butler JA, et al. Long-Term supplementation with selenate and selenomethionine: selenium and glutathione peroxidase (EC 126.96.36.199) in blood components of New Zealand women. Br J Nutr 1993;69:577-88
Conflict of interest
Lumyongsatien et al. investigated the risk of relative selenium (Se) insufficiency for the development of disease severity in 100 patients with Graves' orbitopathy (GO) (1). Thirty-two patients had mild GO and 68 had severe GO, and the adjusted odds ratio (OR) (95% confidence interval [CI]) of Se level ≤93 µg/L for severe GO development was 8.14 (2.39 to 27.75). Abnormal thyroid status was also a risk factor for severe GO, presenting adjusted OR (95% CI) of 3.24 (1.04 to 10.04). The authors concluded that Se ≤93 µg/L was a risk factor for severe GO development, and I have a comment about their study.
The authors conducted a receiver operating characteristic curve analysis to determine the cut-off point for detecting severe GO, but the area under the curve was not so large in Figure 1. In addition, 95% CI for the adjusted OR presented a wide range. This means that ability of differentiating severe GO from mild GO by using serum Se may not be high, although there was a statistical significance. In addition, there is a need of study to specify the dose-response relationship between serum Se levels and severity of GO by including Graves' disease without orbitopathy. Anyway, further study is needed to determine the appropriate cut-off point of serum Se for detecting severe GO.
1. Lumyongsatien M, Bhaktikamala U, Thongtong P, et al. Relative selenium insufficiency is a risk factor for developing severe Graves' orbitopathy: a case-con...
1. Lumyongsatien M, Bhaktikamala U, Thongtong P, et al. Relative selenium insufficiency is a risk factor for developing severe Graves' orbitopathy: a case-control study. BMJ Open Ophthalmol 2021;6(1):e000713.