Selenium and thyroid autoimmunity

Figures & data

Table 1 Localization and function of glutathione peroxidase (Stawicki et al 2007)

Glutathione peroxidase isoenzyme	Localization	Function
GPx 1	Liver, erytrocytes	Important in severe oxidative stress. Role in viral infectious processes
GPx 2	Liver, gastrointestinal tract	First line of defence against ingested organic hydroperoxides. Involvement in apoptosis, cellular proliferation
GPx 3	Plasma, intestine, breast milk, adrenal gland, pulmonary lavage fluid, renal proximal tubules	Thought to have largely regulatory functions associated with oxidative stress and malignancy. Expression induced by hypoxia
GPx 4	Distributed in cytoplasm, nucleus and mitochondria. Expressed in testis, lung, heart, cerebellum. Essential structural component of the sperm’s midpiece	Antioxidant involved in protection of biomembranes. Reduces phospholipids hydroperoxides in cellular membranes. Involved in redox signalling and regulatory processes (apoptosis, inhibition of lipoxygenases). Required for sperm fertilization. Lack of GPx 4 is lethal at an early embyogenic stage
GPx 5	Epididymis	Potentially serves a “backup” function for selenocysteine containing GPx isoforms in sperm. Can be secreted or membrane-bound
GPx 6	Bowman’s gland, olfactory epithelium, embryonic tissues	Olfaction. Putative odorant metabolizing enzyme
GPx 7	Breast tissues	Breast cancer defense against oxidative stress

Abbreviation: GPx, glutathione peroxidases.

Figure 1 Metabolism of thyroid hormones by types 1, 2, and 3 deiodinases.

Table 2 Localizations and functions of selenoproteins other than GPx, DIO, and TrxR

Selenoproteins	Localization	Function
Selenoprotein P	Secreted to plasma by liver	Contains 50% of plasma Se
	Expressed in all tissues	Transport and delivery of Se
		Heavy-metal chelator
Selenoprotein 15	Brain, lung, testis, liver, thyroid, kidney	Involved in glycoprotein folding
		Potential tumor-suppression function
Selenoprotein N	Expressed in all tissues	Plays a pivotal role in muscle tissues
Selenoprotein W	Muscles, heart, intestine, prostate, esophagus, skin	Antioxidant function
		Putative functional role in muscle and brain
Selenophosphate synthetase 2	Expressed in all tissues	Essential component of the Sec biosynthesis machinery
Selenoprotein R	Expressed in all tissues	Repairing of oxidative damaged proteins
Selenoprotein M	Heart, lung, kidney, uterus, placenta, thyroid, brain	Potential role in the brain (low levels are associated with Alzheimer’s disease)
Selenoprotein S	Expressed in all tissues	Link between type 2 diabetes, inflammation, and cardiovascular disease
Selenoprotein K	Heart, muscle, pancreas, liver, placenta	Antioxidant function in the heart

Abbreviation: Se, selenium.

Figure 2 Percentage of patients who had PPTD (left) and hypothyroidism (right) develop in TPOAb(+) women who received Se (group S1) or placebo (group S0), and in TPOAb(−) women (group C)., P < 0.01 copyright © 2007. The Endocrine Society. Reproduced with permission from Negro R, Greco G, Mangieri T, et al. 2007. The influence of selenium supplementation on postpartum thyroid status in pregnant women with thyroid peroxidase autoantibodies. J Clin Endocrinol Metab, 92:1263–8.

StawickiSPLyonsMAloupisM2007Current evidence from phase III clinical trials of selenium supplementation in critically ill patients: why should we bother?Mini Rev Med Chem7693917627581

 PubMed Web of Science ®Google Scholar