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Why is iodine used for metabolic hormones?

Why is iodine used for metabolic hormones?



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Iodine and related biological iodine-carrying hormones are phylogenetically very old, at least according to Wikipedia. Humans use iodine as a metabolic indicator, as do axolotls and apparently most multicellular life.

So why? Growth hormones, sex hormones, et cetera don't require strange heavy elements not used for anything else. It's not a requirement of transcription factors that they contain iodine.

All I've got for hints is that selenium forms an essential part of deiodinases, as well as forming an essential part of thioredoxin reductase. Thioredoxin is a component used to reduce things around the cell, like thiols and RNA bits and so on and so forth, which I could see being worth the evolutionary cost of running down some selenium.

What's the point of iodine? People have iodine deficiency 'all the time' (it's common enough to be named). Is that a product of agriculture somehow? Are there any advantages to using iodine for metabolic hormones? If there are, what are they?


Iodine in us

Iodine is found in two main hormones, T3 and T4. They affect every part of the body, and are important for cell-cell signaling. Wikipedia says:

The thyronines act on nearly every cell in the body. They act to increase the basal metabolic rate, affect protein synthesis, help regulate long bone growth (synergy with growth hormone) and neural maturation, and increase the body's sensitivity to catecholamines (such as adrenaline) by permissiveness. The thyroid hormones are essential to proper development and differentiation of all cells of the human body. These hormones also regulate protein, fat, and carbohydrate metabolism, affecting how human cells use energetic compounds. They also stimulate vitamin metabolism. Numerous physiological and pathological stimuli influence thyroid hormone synthesis.

Why do we have iodine in these hormones?

This is really what your question is. I have found several articles about this and what I found is Iodine is an important catalyst, and Iodotryosines evolved to be important hormones

First, of all, the use of iodine in organisms was ancient. Many prokaryotes and protists used it as a way to deal with reactive oxygen species. Iodide peroxidases were present in primitive oxygenic and photosynthetic Cyanobacteria about 3 - billion years ago. This is because Iodine is one of the most ancient antioxidants.

The thyroxine-like hormones seems to have evolved some 4 Mya in unicellular algae. However, its original function was not for cell-cell signaling as is the case for T3 and T4. It was originally to catalyze other biochemical reactions and scavaging free radicals. This all came about when tyrosine was first created. Iodine reacts with the tyrosine, and forms iodotryosines that were important catalysts for many biochemical reactions.

The first use of Iodotryosines for regulation could have been for ATPase in the mitochondria for non-verterbrate organisms. Also, for vertebrates, the regulation of mtRNA was regulated by iodotryosines.

Iodotyrosines can diffuse between cells very easily, and the development of TH-receptors leaded to the development of thyroxine hormones. Such hormones were used first for embryological development, metamorphosis (if this is the correct term) of amphibians, and more. The rest is really evolution! These hormones are present in virtually all organisms (except prokaryotes).

Summary

In summary, the use of iodine in hormones started with iodine in the first cells as they provide protection against free radicals and reactive oxygen species, while catalyzing biochemical reactions. Iodotyrosines evolved to be important for regulation in cells and finally important in cell-cell signaling.

If you have any more questions, please ask in the comments or we can chat in the Biosphere.

References

These are my sources and there is much more information on these articles. Note that I am not chemically correct about the form of iodine used so these articles have the correct information

http://m.icb.oxfordjournals.org/content/early/2009/06/23/icb.icp053.full.pdf

http://ign.org/cm_data/2011_Venturi_Evolutionary_Significance_of_Iodine.pdf


Classical thyroid hormones implement a very flexible signaling mechanism. Basically, they comprise two aromatic rings that are connected via an oxygen atom. Optionally, they may contain organic side chains and inorganic iodine atoms.

In the case of iodothyronines, which are represented e.g. by the well-known thyroid hormones T4, T3 and 3,5-T2, the side chain contains an amino group and a carboxylate group. Therefore, iodothyronines are amino acids. Up to four different hydrogen atoms (two at every ring) may be replaced by iodine atoms, and the resulting pattern of iodination determines their biological activity. Generally, iodination of the inner ring and deiodination of the outer ring results in high biological activity (e.g. in T3 and 3,5-T2), whereas iodination of the outer ring and deiodination of the inner ring delivers a receptor-blocking thyroid hormone (e.g. reverse-T3). There are three deiodinases encoded by the DIO1, DIO2 and DIO3 genes that catalyze the "step-up" and "step-down" reactions to active or inactive thyroid hormones, respectively. Multiple molecular processes are able to differentially upregulate and downregulate tissue deiodinases. Therefore, thyroid hormones are subject to both global and local control.

Removal of the amino group results in iodothyroacetates. Their biological effects are similar to those of iodothyronines, but in addition to nuclear receptors they also have a strong effect on membrane-bound receptors, which are only weakly activated by iodothyronines.

Thyronamines lack the carboxylate group. Their biological effect is different to that of iodothyronines and iodothyroacetates. By activating the membrane-bound TAAR1 receptor they have an effect that is in most respects antagonistic to that of classical thyroid hormones. Thyronamines seem to be most active in deiodinated state.

Summarizing, both organic and anorganic modifications are able to modulate the effect of thyroid hormones. This mechanism is a very effective way to encode a high grade of information entropy in rather small molecules.

References

Gereben B, Zavacki AM, Ribich S, Kim BW, Huang SA, Simonides WS, Zeöld A, Bianco AC. Cellular and molecular basis of deiodinase-regulated thyroid hormone signaling. Endocr Rev. 2008 Dec;29(7):898-938. doi: 10.1210/er.2008-0019. PMID: 18815314

Engler D, Burger AG. The deiodination of the iodothyronines and of their derivatives in man. Endocr Rev. 1984 Spring;5(2):151-84. PMID 6376077.

Piehl S, Hoefig CS, Scanlan TS, Köhrle J. Thyronamines--past, present, and future. Endocr Rev. 2011 Feb;32(1):64-80. doi: 10.1210/er.2009-0040. PMID 20880963.


here is an interesting article:

The accumulation of radioactive iodine by Amphioxus

summarizing the abstract: it's about cephalocordates that are not vertebrate, so they are close relatives (most related to the ancestors of) the vertebrate. The specific cephalocordate in question is amphioxus.The article talks about a specific gland called the "endostyle" of Amphioxus and it explored the homology with the subpharyngeal gland of the larval form of lampreys (an agnathan, the most primitive of vertebrate) called ammocoete. The sub pharyngeal gland is sort of the same thing as the thyroid. In fact this sub pharyngeal gland or thyroid is a defining characteristic of vertebrate. The abstract describes an experiment where they took the endostyle from amphioxus and implanted it into a salamander (and amphibian) and it had effects similar to the thyroid gland. This means that this mucous producing gland in the cephalocordates produces compounds that have effects similar to the thyroid

Why does the endostyle produce mucous? Because it is essential for their filter feeding (feeding by straining suspended matter and food particles from water).

Why concentrate iodine in the mucous, I don't know.

The other answers explain the function of iodine. This answer was to explain the evolution of iodine concentrating glands at the very beginning of our vertebrate ancestors.


How Does Iodine Help With Weight Loss? Learn More

Iodine deficiency causes a lot of problems for individuals who have issues with their thyroid. If you are feeling tired, fatigued, overweight, and moody, then you could have an iodine deficiency.

There are a lot of thyroid functions that can be exacerbated by those who don’t have any iodine in their systems. Studies show that this deficiency affects 95% of patients who also have thyroid problems.

A DNA Health Testing Kit can help you take the guesswork out of your needs by providing scientific tailored custom health plans.

So how can you know if you have an iodine deficiency?

You may want to see if you have symptoms of this deficiency as well:

  • Dull and brittle hair
  • Balding
  • Gray or dulling skin tone
  • Low energy levels
  • Poor concentration
  • Depression
  • Low thyroid functions
  • Inability to deal with cold temperatures
  • Weak heartbeat
  • Weight gain

Typically iodine deficiency can lead to low concentration and hypersensitivity to cold, characterized by cold feet and hands.

It can also affect your metabolism. One of the major causes for this is because organic vegetables have become more popular, while still not getting enough iodine from the soil.

Table salt can help to balance out the levels of iodine in the bloodstream, but now with lowered salt intake, there have been increasing cases of iodine deficiency.


Thyroid hormones

The two thyroid hormones are

T4: Thyroxine (also called tetraiodothyronine)

T4, the major hormone produced by the thyroid gland, has only a slight effect, if any, on speeding up the body’s metabolic rate. Instead, T4 is converted into T3, the more active hormone. The conversion of T4 to T3 occurs in the liver and other tissues. Many factors control the conversion of T4 to T3, including the body’s needs from moment to moment and the presence or absence of illnesses.

Most of the T4 and T3 in the bloodstream is carried bound to a protein called thyroxine-binding globulin. Only a little of the T4 and T3 are circulating free in the blood. However, it is this free hormone that is active. When the free hormone is used by the body, some of the bound hormone is released from the binding protein.

To produce thyroid hormones, the thyroid gland needs iodine, an element contained in food and water. The thyroid gland traps iodine and processes it into thyroid hormones. As thyroid hormones are used, some of the iodine contained in the hormones is released, returns to the thyroid gland, and is recycled to produce more thyroid hormones. Oddly, the thyroid gland releases slightly less of the thyroid hormones if it is exposed to high levels of iodine transported to it in the blood.

The thyroid gland also produces the hormone calcitonin , which may contribute to bone strength by helping calcium to be incorporated into bone.


Use by the Thyroid

The human thyroid has an iodine “trap” which captures iodides and holds them until they are converted into triiodothyronine (T3) and its prohormone, thyroxine (T4). T3s and T4s are shortened references to two very important hormones that are produced by the thyroid gland to regulate the body’s metabolism. This is only one of the uses of iodine in the body.

Now that you have learned the general differences between iodine and iodide, you will no longer be confused about potassium iodide and iodine. For more details on health benefits and usage information, or if you have any questions, comments, or concerns, feel free to contact the experts at Magnascent. We look forward to helping you understand the difference between iodine and iodine.

“Iodide is first oxidized either into nascent iodine I0 or I3-. The enzyme peroxidase is necessary as well as hydrogen peroxide. Then, iodine is attached to tyrosine which is the precursor of the thyroid hormones. Monoiodotyrosine and diiodotyrosine are formed by tyrosine iodinase.” [Ref 1.]


Thyroid Hormones Control Your Metabolism (940 words)

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Thyroid hormones control your metabolism

The endocrine system is where the manufacturing and delivery of chemical messengers called hormones take place. The specialized tissues that make hormones are called glands when the hormones are released and reach the targeting cells, they switch on or off specific functions. Some hormones can also enter the nucleus and allow expression of some genes. Thyroxine, also called 3,5,3′,5′-tetraiodothyronine (T4), is a hormone that is produced in the thyroid gland. The thyroid gland is located in front of the neck, just below the Adam’s apple, and it is made up of two halves called lobes. Thyroxine hormone is formed of amino acid tyrosine and iodine (chemical element that derives from food), each tyroxine binds four iodines the thyroid cells are the only that adsorb iodine. Another hormone produced in the thyroid gland is triiodothyronine, 3,3′,5-triiodothyronine (T3).

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How Iodine Deficiency Affects the Thyroid

Iodine deficiency is a serious issue and the number one cause of preventable mental disabilities in the world. The World Health Organization estimates that around 1 billion people will suffer from some form of health issue due to a lack of iodine in the diet, and approximately 40 percent of the world’s population is at risk for iodine deficiency. [13, 14, 15] Although table salt has been iodized since 1924, iodine deficiency is rising again in the Western world. A 1998 report found that iodine deficiencies had increased in the United States during the previous 20 years, likely due to dietary changes. [16]

Insufficient iodine intake directly affects the thyroid since T3 and T4 hormones require this essential mineral. If you do not have enough iodine, you can not produce enough of these two thyroid hormones. These iodine-containing hormones are used for brain, heart, muscle, and bone maintenance and functioning, as well as metabolism &mdash turning food nutrients into the energy required for the body and its organs to work properly.


Excess Iodine

Given the strong link between iodine and thyroid health, it's reassuring to learn that iodine deficiency is rare in the United States and other developed countries where iodized salt is used. Indeed, as an International Journal of Molecular Sciences study reported in 2014, iodine excess is currently a more frequent occurrence in these places. This, though, is not without concern.  

For some people with abnormal thyroid glands, excessive iodine can trigger or worsen hypothyroidism. While initially, you may have more energy, high doses can cause an "iodine crash" that leaves you feeling exhausted and achy within a few days.

That's because high iodine intake can initiate and exacerbate infiltration of the thyroid by lymphocytes, the white blood cells that accumulate due to chronic injury or irritation.

In addition, large amounts of iodine block the thyroid's ability to make thyroid hormones. A 2014 study in the journal Endocrinology and Metabolism found that more-than-adequate or excessive iodine levels are unsafe and may lead to hypothyroidism and autoimmune thyroiditis (Hashimoto's thyroiditis, chronic lymphocytic thyroiditis), especially for people with recurring thyroid disease.  

Women who take too much supplemental iodine during pregnancy may give birth to babies with congenital hypothyroidism, a thyroid deficiency that, if left untreated, can lead to mental, growth, and heart problems, according to a 2012 study published in The Journal of Pediatrics.  

While iodine poisoning is rare, the overconsumption of iodine can be just as problematic as consuming too little.

Are You Getting Enough or Too Much?

While iodine can be detected in urine, relying on such a test is not helpful, since 90 percent of the iodine you ingest is quickly expelled. Rather, doctors use thyroid tests to determine if your iodine intake is concerning or not.

In addition, iodine deficiency is typically suspected based on the development of goiter, hypothyroidism, or congenital hypothyroidism (low thyroid function at birth).  

Be sure that any adjustments you make to your iodine intake, whether you have a circumstance that seems to call for them or not, are cleared by your doctor first.


Why Do I Need Iodine?

Proper human development and metabolic function require iodine. It combines with tyrosine, an amino acid, to form two of the most important thyroid hormones that regulate metabolism, thyroxine (T4) and triiodothyronine (T3). Too little iodine during fetal development and childhood can cause developmental concerns. Studies have found a lack of iodine leads to reduced mental development and lower IQ. [1 , 2] Functional imbalance results from too much or too little iodine and lead to long-term concerns such as hypothyroidism and hyperthyroidism. Without proper iodine consumption, the human body simply doesn't work normally.


How Can You Get Enough Iodine?

Odds are you are eating many whole foods, which already contain iodine. Among these are seaweed, high-quality seafood, eggs, strawberries, cranberries, dairy products, and dark green leafy vegetables. Sadly, because of poor soil quality and other factors in our toxic world, this may not be enough.

A study conducted by Royal North Shore Hospital in St. Leonards, Australia, found that 74% of healthy adults may not be getting adequate amounts of iodine through diet alone [20].

In addition, holistic health experts agree that relying on iodized table salt to get the right amount of iodine is not a wise option. This is because in order to produce commercial salt in the cheapest way possible, today’s manufacturers rely on harsh chemicals, which eventually wind up sprinkled on our dinner plates [21].

When it comes to iodine supplements, choose only the best.

Keep your standards high when it comes to iodine supplementation. Remember that iodine is the food of the thyroid, and the thyroid is the “command center” of all your hormones! You wouldn’t put junk into your mouth to feed your body, would you? Don’t put it in your thyroid either!

Iodine deficiency is widespread, not just in the U.S., but also globally. The World Health Organization estimates that roughly two billion people worldwide suffer from some form of iodine deficiency [22].

Don’t be another statistic. Stand out from the crowd by enjoying all the amazing health-supporting benefits that iodine can provide!

When your organs are working hard to detoxify, you want the purest form of iodine possible to help them work more efficiently. It only makes sense to use an organic form that’s totally natural and free of chemicals. Organixx Iodine is one of the only formulas that is USDA Certified Organic. It’s a pure, nascent form of iodine which your thyroid can use immediately.

Sources:


Understanding Thyroid Metabolism

Health care providers often face patients complaining of symptoms that appear to be related to hypothyroidism. These symptoms can include fatigue, weight gain, hair loss, cold intolerance, constipation, decreased concentration, depression, dry skin, infertility, hyperlipidemia, irregular or heavy menses, memory impairment and muscle aches [Source: Milner]. In some patients with these symptoms, TSH and T4 levels can be within normal limits, which could lead health care providers to rule out low thyroid function. However, thyroid metabolism is complex, and each step can be influenced by nutrition, prescription medications and lifestyle factors. Considering these influences can help practitioners in their understanding of how patients can suffer from symptoms of hypothyroidism even when their blood levels appear normal.

The thyroid hormone process begins when the pituitary gland in the brain produces thyroid-stimulating hormone (TSH). TSH then acts upon the thyroid gland to produce thyroid hormones. The two main thyroid hormones produced are thyroxine (T4) and triiodothyronine (T3). Although the thyroid gland produces more T4 (80 percent) compared with T3 (20 percent), T3 is 300 percent more active than T4 and is the thyroid hormone responsible for increasing metabolism. In fact, much of the T4 is converted into the more active T3 inside the cells of the body. Once the brain senses the thyroid gland has produced enough thyroid hormone, it will decrease TSH production. Through this negative feedback loop, the production of the thyroid hormones is slowed [Source: Brownstein].

Problems may arise when outside factors act upon the thyroid metabolism cycle which can lead to disruptions in TSH levels, decreased production of T4, incomplete conversion of T4 to T3 or imbalance in the ratio of T3 to reverse T3. High levels of cortisol caused by stress, for example, can suppress the production of TSH, leading to symptoms of hypothyroidism due to low hormone production. The thyroid gland could also appear to be functioning normally if TSH is the only blood level tested and it is being artificially suppressed by high cortisol levels [Source: Paoletti].

The production of T4 might also be disrupted. T4 is produced by the thyroid gland and is comprised of iodine and the amino acid tyrosine. If there is a lack of sufficient quantity of tyrosine or iodine, the production of T4 can be compromised [Source: Paoletti].

Incomplete conversion of T4 to T3 can also lead to low thyroid symptoms. T4 receptors in the body have not yet been identified therefore, T4 needs to be converted in the peripheral tissue to the more active thyroid hormone T3 in order to relieve low thyroid symptoms. T4 is converted into T3 by removing an iodine from the T4 molecule at the 5’ position [Source: Paoletti]. Factors such as nutritional deficiencies and medications can inhibit this conversion. Nutritional deficiencies such as iodine, iron, selenium, zinc, vitamin A, riboflavin, pyridoxine and B12, along with the use of certain medications including beta blockers, birth control pills, estrogen, iodinated contrast agents, lithium, phenytoin and theophylline can inhibit the conversion of T4 into T3. Other factors that can cause this inhibition include aging, alcohol, alpha-lipoic acid, diabetes, fluoride, lead, mercury, pesticides, radiation, stress and surgery [Source: Brownstein].

Problems can arise if T4 is converted preferentially to reverse T3. Reverse T3 can bind to the T3 receptor, but it only has 1 percent of the activity of T3. T4 is normally converted into equal amounts of T3 and reverse T3. However, if there is a preferential conversion of T4 to reverse T3, the reverse T3 can act as an antagonist to T3 at the receptor level. This scenario leads to symptoms of low thyroid since reverse T3 can be considered inactive. Factors that may lead to a preferential conversion to reverse T3 include high cortisol, glucocorticoids, stress, excess estrogen and nutritional deficiencies such as selenium, iodine, zinc and iron [Source: Paoletti].

Symptoms of low thyroid can also be caused by factors not related to thyroid metabolism. Factors such as thyroid receptor numbers and their ability to function properly can play an important role in thyroid function. Cortisol levels need to be within normal range (morning saliva level of 3.7 to 9.5 ng/mL) and vitamin D levels need to be between 50 to 70 ng/mL for thyroid receptors to respond properly. Iron also plays an important role in thyroid hormone synthesis. Thyroid peroxidase activity depends on iron therefore, iron deficiency could lead to hypothyroidism. Ferritin levels may need to be in the range of 90-110 to achieve proper thyroid function [Source: Paoletti].

This view inside thyroid metabolism helps to illustrate the many factors besides TSH and T4 levels that may be necessary in evaluating thyroid function. Evaluating TSH, free T4, free T3, reverse T3, thyroid antibodies, cortisol, vitamin D, ferritin, medication use and nutritional habits all can help health care providers determine the cause of a patient’s thyroid symptoms, and an appropriate care plan can be developed. Nutritional deficiencies can be corrected, lifestyle habits can be addressed and medication dosages can be adjusted based on a detailed patient history and evaluation of the lab values mentioned previously. If thyroid replacement is necessary, health care providers can utilize a commercially available thyroid medication, or they can contact a compounding pharmacist to prepare customized therapy with specific amounts of T4 and T3 based on that particular patient’s needs.


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