Iodine- RDA- 15ug for men and women- Sourceso Plants/Animals- varies greatly (soil and water content)o Fortified- Iodized salt- Digesiono Eaten Bound to amino acids Free as Iodine (3-) or Iodide (1-)o Absorption Through GI (including stomach)o Iodine found in Thyroid Gland (18%) Small amounts in the ovaries, placenta, skins, gastric, saliva Kidneys- for excretions- Functiono Synthesis of thyroid hormones Thyroxine (T4) Triiodothyronine (T3)o Thyroid gland Growth Development Regualtion of BMR - Hyperthyroidism- increased BMRo Leaking proteins, burning glucose and no ATP yield- Hypothyroidism- decreased BMRo Burning fever glucoseo Work harder to maintain weight- Thyroid o Formation of Thyroid Hormones Thyroid cells collect Iodide- via Na/K ATPase Pump (60mg day) IodineIodide Iodide binds to tyrosine residue- MIT (mono) MIT iodinates to DIT (dio) DIT + MIT= Triiodothyronine (T3) DIT + DIT= Thyroxine (T4)- Higher concentrations than T3- T4T3 (if needed)- Se dependento Regulation of Thyroid Gland Hypothalamus- Small part of the brain above Pituitary gland- Produces thyrotropin releasing hormone (TRH) which stimulates the release of TSH o Explained in pituitary gland Pituitary Gland- Located at the base of the brain - Produces TSH o Decreased levels of thyroid hormone in blood stimulates this release TSH:- Stimulates thyroid hormone production- Causes growth of thyroid cells- Lets Break it downo Hypothalamus releases TRHPituitary Gland for TSHThyroid T3and T4 First 2 steps are Grn dependent Last step is Iodine Dependent- Deficiency o Causes decreased synthesis of T3/T4Stimulates TRH/TSHIncreased Growth of thyroid cells Persistent low levels of iodine causes and increased size of thyroid glando Goiter- enlargement of thyroid gland Diseases, pregnancy, and puberty- Interactionso Goitrogens- substances that inhibit iodine metabolism and thyroid hormone synthesis Lithium- used to treat bipolar disorders Thiocynated foods- prevent the uptake of iodine at the thyroid gland- Cabbage, kale, cauliflower (no evidence to cause goiter)- Cassava- consumed in large enough amounts in 3rd world countries to be directly related to goiter formation- Toxicity- noneVitamin A- Tony Berardi typed this part1. Explain the retinoids and cartoenoids.- You have two main types of Vitamin A, the retinoids and the carotenoinds. The retinoids are the active form, these are the retinal, retinol, retinoic acid, and retinyl esters. The cartoenoids are the provitamins. These get cleaved in the body to retinal, which is later reduced to retinol. Such as beta-carotene, beta-cryptoxanthin, lycopene, lutein, and zeaxanthin (so any weird named molecule)2. What are the sources for both types?- The carotenoids are the form that is in the veggies, like carrots. Most colorful veggies are full of them; there are over 600. The retinoids are in animal products. The best sources are egg yolks, butter, and milk. The form in supplements is Retinyl palmitate/acetate or some have carotene.Since vitamin A is not found in low fat dairy and some breakfast items, it is supplemented at around 500 IU. Supplement pills contain 3000-25000 IU. The RDA is around 5000 IU or 900 REA 1 RAE is equal to 1ug retinol, or 12ug beta carotene, or 24 ug other some other carotenoid. 3. How is it digested, absorbed, and transported?- In food, it is in the form as either carentoids or retinyl esters attached to a protein, so just like all the other nutrients we learned, it has to be cleaved out ofthe protein. First pepsin (or HCl) cleaves out the free retinols or carotenoids, and these free carentoids and the retinols then form micelles just like lipids do when they get absorbed (meaning it enters via lymph, not the blood stream, as it is a fat soluble vitamin. Retinol is 70-90% absorbed and carotenoids are 20-50%. They then go to their target, so either the retina, bone, kidney, intestine, or gonad. In order tocirculate in the plasma, they need a protein called Retinol Binding Protein, orRBP. Each mole of retinol combines with one mole of RBP to form a holo-RBP. So it is a one to one ratio. Once you have your holo-RBP, this will react with another protein called transthyretin. This complex (now a RBP-TTR) will then go to the tissues.- So you have a free retinol, it will combine with a RBP, and this will then combine with a TRR. This is the circulating form. When the retinol is deposited in whatever tissue it goes to, the RBP and the TTR will be released to bind to another free retinol.- Depending on its target tissue, it will have a different binding protein, called the cellular retinol binding protein or CRBP. CRBP 1 for the liver and kidney CRBP 2 for the intestine CRBP 3 for the muscle and heart CRBP 4 for the colon.4. What are the functions?- Everyone knows the main function of vitamin A is for eyesight, but also for other systemic actions, such as cell differentiation/growth/reproduction/bone and immune development. How it works for vision is this: Retinal (11-cis retinal) is the form that the eyes use. The 11-cis retinal will bind with opsin (protein in the retina) to form rhodopsin. This rhodopsin helps communicate the light signal to the brain, and will break down to all-trans retinal. As this process always happens when we see light, we have to replace the 11-cis retinal in our diet (that is the retinol that is in animal products)- For the other functions involve the other forms. Retinal is oxidized to retinoic acid. Cell differentiation involves retinoic acid Growth is both retinoic acid and retinol. By remodeling the epiphsyseal cartilage. Fertility is retinol Immunity is retinoids and carotenoids Skin integrity is retinoic acid. Gene expression via retinoic acid binding to RAR receptors to induce transcription. Then the last function is as an antioxidant. The carotenoids are the best antioxidants. The carotenoids function to prevent macular degeneration and inhibit LDL oxidation. 5. How do you assess?- There are many tests for vitamin A assessment. One is the serum retinol test, but this a nonspecific test. The serum carotenoid test, but this is reflective of what you just consumed. The best is the relative dose response, or RDR. This test measures the storage amount in the liver. First you measure their plasma retinol, then you give them an oral
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