Iodine, zinc and selenium
- 1. Trace element-II Binaya Tamang UCMS Department of Biochemistry
- 2. Iodine • Iodine is an imperative micronutrient • for the normal thyroid function necessary for the normal growth and development of our brain and body . • inevitable micronutrient involved in the synthesis of thyroid hormones: • Thyroxine (T4) and Triiodothronine (T3)
- 3. DISCOVERY • Iodine was isolated by French chemist, Courtois, in 1811, • who accidentally discovered iodine as the violet vapour • arising from the seaweed ash • while manufacturing gunpowder for Napoleon’s army.
- 4. • In our human body, approximately 15-20 mg of iodine is present, of which 70-80 % is concentrated in the thyroid gland • Approximately 90% of the dietry iodine is absorbed in the upper small intestine after being converted into the iodide ion in the gut lumen. • iodine deficiency may cause a mental and physical disabilities, collectively called as iodine deficiency disorders (IDD)
- 5. Affects all age group • Iodine deficiency affects the populations of all age group with • pregnant woman and children forming most vulnerable groups. • Deficiency during childhood reduces somatic growth, cognitive and motor function
- 6. • Salt is the food ingredient that is consumed by the general population on the daily basis. If fortified with the iodine it is called as Iodized salt • Mainly, two organs i.e., thyroid gland and kidneys are responsible for the clearance of iodine from the plasma
- 7. Urinary iodine concentration • For a recent iodine intake, • the most sensitive marker is urinary iodine concentration (UIC) • because 90% of the iodine absorbed by the body eventually appears in urine • and therefore, is the index of choice for evaluating degree of iodine deficiency and its correction
- 8. DIETARY SOURCES • Seafoods, drinking water, vegetables, fruits (grown on seaboard). • High altitudes are deficient in iodine content in water as well as soil. • Plant and animal foods of these areas, therefore, contain lesser amount of iodine. • In these regions, iodine is added to drinking water or to table salt.
- 9. Plasma iodine • 4-10 mg/dl. • Most of this is present as protein bound iodine (PBI). • RBC do not contain iodine.
- 10. Dietary requirements • Adults-100-150 μg/day • Pregnant woman- 200 μg/day
- 11. METABOLISM OF IODINE • iodine in our food has reduced to iodide. • iodide form is taken up in the stomach and throughout the small intestine via mucous membrane they finally reach in to the blood • Iodine is transported into thyroid by sodium iodide symporter (NIS) against concentration gradient • The body of a healthy adult contains 15 to 20 mg of iodine, of which 70 to 80% is in the thyroid • A transmembrane NIS, transfers iodide into thyroid tissue at 20 to 50 times higher than in the plasma.
- 13. Goitrogenic substances Interferes with the production of thyroid hormones • Thiocynates • Nitrates • Perchlorates • Drugs like thiouracil and thiourea • Certains vegetables like cabbage, cauliflower and turnip- containg goitrogenic factors ( mostly thiocynates).
- 15. Iodine disorders Hypothyroidism • Myxoedema • cretinism Hyperthyroidism • Grave’s disease
- 16. ZINC (Zn) • Total content of zinc : 2g • out of which 60% is in skeletal muscles and 30% in bones. • Highest concentration of zinc is seen in hippocampus area of brain and prostatic secretion. • RBCs contain Zn ( 1.5 mg/dl) in association with carbonic anhydrase.
- 17. dietary sources • grains, beans, nuts, cheese, meat and shellfish. • Zinc and copper will competitively inhibit each other's absorption. • So, zinc is therapeutically useful to reduce copper absorption in Wilson's disease
- 18. Absorption • Mainly in the duodenum • Zn absorption appears to be dependent on transport protein- metallothionein. • Copper, calcium, cadmium, iron and phytate will interfere with the absorption of zinc. • In liver, zinc is stored. • Zinc is excreted through pancreatic juice and to a lesser extent through sweat.
- 19. FUNCTIONS Essential component of several enzymes e.g. • Carbonic anhydrase, • alcohol dehydrogenase • Alkaline phosphatase • carboxy peptidase • superoxide dismutase ( cytosolic) Antioxidant since, the SOD protects from free radicals The storage and secretion of insulin from beta cells of pancrease require Zn
- 20. • Zn is require to maintain normal level of vitamin A in serum. Zn promotes the synthesis of retinol binding protein. • It is required for wound healing. Zn enhances cell growth and division, besides stabilizing biomembranes. • Gusten, a zinc containing protein of saliva, is important for taste sensation
- 21. • Zn is essential for proper reproduction function. • Zinc deficiency also lowers spermatogenesis in males and menstrual cycles are disturbed in females. • Prasad et al have shown that zinc deficiency may lead to ‘dwarfism’ and ‘hypogonadism’. • In such dwarfs, zinc concentration in plasma, red blood cells, hair, urine and faeces was found to be less than control subjects.
- 22. Clinical aspects • Acrodermatitis enteropathica: is a rare inherited metabolic disease of zinc deficiency caused by defect in the absorption of Zn from the intestine. • Zinc toxicity is often seen in welders due to inhalation of zinc oxide fumes. • Nausea, gastric ulcer, pancreatitis, anemia and excessive salivation.
- 23. Deficiency • growth retardation, poor wound healing, anemia, loss of appetite, loss of taste sensation • Neuropsychiatric of chronic alcoholism may be partly due to Zinc deficiency.
- 24. Selenium • In mammals, glutathione peroxidase (GP) is the important selenium containing enzyme. • Selenocystein is component. • RBC contains good quantity of glutathione peroxidase. • 21 st amino acid. • Protects the cell against the damage caused by H2O2.
- 25. • Thyroxin is converted to T3 by 5'-de-iodinase, which is a selenium containing enzyme. In Se deficiency, this enzyme becomes less active, leading to hypothyroidism. • Selenium acts as a nonspecific intracellular anti- oxidant. This action of Se is complementary to vitamin E. • In Se deficiency, tissue vitamin E content is depleted.
- 26. Keshan disease • In Keshan province in China, the soil is deficient in selenium. This leads to prevalence of Keshan disease. • It is characterized by multifocal myocardial necrosis, cardiac arrhythmias and cardiac enlargement.
- 27. Selenosis. • Selenium toxicity is called selenosis. • Selenium is present in metal polishes and anti- rust compounds. • symptoms include hair loss, falling of nails, diarrhea, weight loss, and garlicky odor in breath.
- 28. Thank You