The Benefits of Selenium on Thyroid Health

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The Benefits of Selenium on Thyroid Health

• Alyson Branton
• HNU 461
• April 1st, 2009

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Outline

• Review of thyroid function
• Introduction to selenium
• Role of selenium on hormone metabolism
• Protective, anti-inflammatory effects
• Conclusion
• Questions

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Thyroid Gland

• Small, butterfly shaped endocrine gland, located
  at the base of the neck
• Hormones it secretes are essential to all growth
  and metabolism
• Two most important are tetraiodothyronine
  (thyroxine or T4) and triiodothyronine (T3)
• Thyroid Stimulating Hormone from pituitary gland
  stimulates production of T4
• type 2 5-deiodinase
• T4(inactive)----?-----? T3(active)
  (in cells)

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Prevalence of Diseases

• Estimated that one in every three Canadians has a
  thyroid disorder!
• Diseases include
• Hypothyroidism (underactive thyroid)
• Thermogenesis and the basal metabolic rate are
  decreased? weight gain
• Hyperthyroidism (overactive thyroid)
• Thermogenesis and the basal metabolic
  rate are increased? weight loss
• Graves eye disease
• Thyroiditis (Hashimotos, postpartum)
• Cancer of the thyroid

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Selenium

• A trace mineral that is required in small amounts
  for human health
• Is a component of the amino acids
  selenomethionine and selenocysteine.
• Occurs naturally in selenium rich soils
• High levels found in Brazil nuts, cereals, meat,
  fish, eggs, kidney, tuna, crap and lobster.

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Significance of selenium on thyroid

• The iodothyronine deiodinases (selenium
  containing enzymes) are required for the
  conversion of biologically active T3 from T4
• The selenoenzymes, glutathione peroxidase (GPx)
  and thioredoxin reductase are crucial to the
  protection of the thyroid from hydrogen peroxide.
  
• If peroxides are not neutralized, damage can lead
  to an overactive or underactive thyroid.
• Thyroid is sensitive to both Se excesses and
  deficiencies supplied in the diet.

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Selenium deficiency

• First case of hypothyroidism caused exclusively
  from Se deficiency documented by Pizzulli and
  Ranjbar (2000)
• Three children were presented with clinical
  symptoms of hypothyroidism including
  central-vegetative symptoms, muscle weakness,
  alopecia (hair loss) and delayed fontanel
  closure.
• Se levels were low in all patients (32-43 µg/L)
• After four weeks of Se treatment, both, the
  parameters of the thyroid gland and the level of
  Se had returned to normal. Also seen were marked
  clinical improvements in all three cases.
• Based on this evidence, it can be assumed that
  the reason for hypothyroidism seen in these cases
  were a result of reduced activity of type 2
  5-deiodinase caused by Se deficiency.

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Adverse effects of selenium

• To the contrary, adverse effects on thyroid
  hormone metabolism in men fed foods naturally
  high in Se observed by Hawkes and Keim
• Diets high in Se led to decreased energy
  expenditure and observed weight gain. Along with
  decreases in serum T3 and compensatory increases
  in serum TSH suggest that a subclinical
  hypothyroid response was induced by the high Se
  diet.
• Diets low in Se led to increased expenditure and
  observed weight loss. The additional increases in
  serum T3 and serum triacylglycerols accompanied
  by losses of body fat suggest that a subclinical
  hyperthyroid response was induced by the low Se
  diet.

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High Se intakes contd

• Raymen (2008) found no effect of daily
  supplementation with 100, 200, or 300 µg of high
  Se yeast on thyroid hormones in elderly UK
  residents.
• This suggests that Se intake is adequate for
  thyroid function in the UK regions but it might
  not hold true for elderly persons living in areas
  of lower selenium intake.
• Also suggests no adverse effects of Se on thyroid
  metabolism were seen up to a total intake (food
  plus supplement) of 350 µg/d

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Protective effect of Se on pregnant women

• Pregnant women who are positive for thyroid
  peroxidase antibodies TPOAb() are prone to
  develop postpartum thyroid dysfunction (PPTD)
• and permanent hypothyroidism.
• Negro et al. (2007) found 200 µg/d Se
  supplementation significantly reduced the
  incidence of PPTD in TPOAb() women while thyroid
  hormone concentrations were not affected.
• Thus, Se influences anti-inflammatory activity by
  maximizing GPx activity without affecting
  thyroid hormone levels.

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Benefits for people with autoimmune thyroiditis

• Autoimmune thyroiditis (AIT) is a condition when
  antibodies are produced against thyroid
  peroxidase (TPOAb)
• Turker et al (2000) found oral administration of
  200 mg Se/day decreases serum TPOAb titers
  effectively in all age groups.
• Also found that suppression of autoimmune
  activity not restricted to deficiency state- Se
  effective treatment for people with adequate
  initial stores

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Conclusions

• Intricate relationship between Se and thyroid
  function, influencing both metabolism and
  demonstrating a protective immunological effect.
• Selenium has potential as a treatment option for
  hypothyroidism.
• Key is to make sure your diet provides enough
  (but not too much) Se to promote optimal thyroid
  function
• Se is a particularly beneficial treatment option
  for certain populations such as people with AIT
  and pregnant women who are TPOAb().
• This seems to be effective on both people with Se
  deficiency and those with adequate initial serum
  levels.
• Se may enhance immunocompetence without affecting
  thyroid hormone levels in these situations.

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References

• Duntas, L. H., Mantzou, E., Koutras, D. A.
  (2003). Effects of a six month treatment with
• selenomethionine in patients with autoimmune
  thyroiditis. European Journal of
• Endocrinology, 148(4), 389-393.
  doi10.1530/eje.0.1480389
• Hawkes, W. C., Keim, N. L. (2003). Dietary
  selenium intake modulates thyroid hormone and
• energy metabolism in men Electronic version.
  Journal of Nutrition, 133, 3443-3448
• Negro, R.., Greco, G., Mangieri, T., Pezzarossa,
  A., Dazzi, D., Hassan, H. (2007). The
• influence of selenium supplementation on
  postpartum thyroid status in pregnant women
• with thyroid peroxidase autoantibodies. Journal
  of Clinical Endocrinology
• Metabolism, 92(4), 1263-1268. doi10.1210/jc.2006
  -1821
• Pizzulli, A., Ranjbar, A. (2000). Selenium
  deficiency and hypothyroidism. Biological Trace
• Element Research, 77(3), 199-208. doi
  10.1385/BTER773199
• Rayman, M. P., Thompson, A. J., Bekaert, B.,
  Catterick, J., Galassini, R., Hall, E., et al.
  (2008).
• Randomized controlled trial of the effect of
  selenium supplementation on thyroid
• function in the elderly in the united kingdom
  Electronic version. American Journal of
• Clinical Nutrition, 87(2), 370-378.
• Turker, O., Kumanlioglu, K., Karapolat, I.,
  Dogan, I. (2006). Selenium treatment in
• Autoimmune thyroiditis 9-month follow-up with
  variable doses Journal of
• Endocrinology, 190, 151-156. doi10.1677/joe.1.06
  661
• Van Bakel, M. M. E., Printzen, G., Wermuth, B.,
  Wiesmann, U. N. (2000). Antioxidant and

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Thank you for listening!! Questions?