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Vitamin B-12 Deficiency and Hypothyroidism
Vitamin B12 is a complex and important B vitamin in the body. Its deficiency is closely related to folate deficiency and both deficiencies can cause severe damage to the heart and brain. However, vitamin B12 deficiency is also related to hypothyroidism. Find out how vitamin B12 deficiency can reduce the production of thyroid hormones and how you can improve thyroid function through supplements.
by Brad Chase
Vitamin B12 is a water-soluble B vitamin also known as cobalamin.
There are 4 forms of vitamin B12: cyanocobalamin, hydroxocobalamin, methylcobalamin and adenosylcobalamin. While cyanocobalamin is the most popular form, it has to be converted to the two active vitamers, adenosylcobalamin and methylcobalamin, before the body utilizes the vitamin.
Vitamin B12 is found in every cell of the body. It is required for cellular metabolism and energy production, the production and regulation of the DNA and for fatty acid metabolism.
Plants and animals do not produce vitamin B12. Rather, they obtain it from bacteria in the form of hydroxocobalamin. During the purification of bacteria-derived vitamin B12 with activated charcoal, it picks up cyanide and becomes cyanocobalamin.
Animals are generally better sources of vitamin B12 than plants. Dietary sources of this vitamin include fish, poultry, meat, eggs, seafood and dairy products.
Fortified cereals are also an excellent source of vitamin B12 especially for vegetarians and vegans and adults older than 50 years.
The recommended daily dietary intake of vitamin B12 is 2 – 3 micrograms per day for adults.
Pregnant and lactating women need more vitamin B12. Therefore, their daily recommended intake is closer to the upper limit of the adult values.
The primary medical use of vitamin B12 is for treating a deficiency in vitamin. The hydroxocobalamin form of the vitamin is also used to treat cyanide poisoning because it picks up cyanide to become cyanocobalamin, a harmless compound and another form of vitamin B12.
Vitamin B12 deficiency is the name given to a medical condition that is caused by a low blood level of vitamin B12.
A recent study found that vitamin B12 deficiency affects more people than previously believed. This high rate of a silent but widespread deficiency is due to the nature of the deficiency. Even though most people consume enough vitamin B12 in their diets, a deficiency can still result if the vitamin is not extensively absorbed into the blood.
The body stores 2 – 5 mg of vitamin B12 and half of the stored amount can be found in the liver.
However, about 0.1% of the vitamin B12 in the body is lost every day. Therefore, there is a need for constant supplementation.
Vitamin B12 deficiency can lead to severe and permanent damage to the cardiovascular and nervous system.
This deficiency causes the accumulation of homocysteine and methylmalonic acid. Because folic acid can also cause the accumulation of homocysteine, methylmalonic acid is a more specific indicator of vitamin B12 deficiency.
Homocysteine is a stop-gap metabolite in amino acid synthesis, and vitamin B12 is required as a cofactor to drive the conversion of homocysteine to the amino acid, methionine. When homocysteine accumulates, it can be toxic and cause damage to the heart and nerves.
Vitamin B12 deficiency causes pernicious anemia which is a disease complex including megaloblastic anemia as well as gastrointestinal and neurological damage.
Mild symptoms of vitamin B12 deficiency include fatigue, depression and memory impairment. These are caused by damage to nerves (due to the accumulation of homocysteine and methylmalonic acid) and low neurotransmitter levels (because of the impaired synthesis of methionine, a precursor of many neurotransmitters).
Vitamin B12 deficiency can also cause ataxia, poor reflexes and impaired sensory perception. In severe cases, it can result in mania and psychosis.
Hypothyroidism is also another deficiency state but it is a deficiency of thyroid hormones.
Although iodine deficiency is the chief cause of hypothyroidism, the medical condition can also be caused by other factors including stress.
There are 2 major hormones secreted from the thyroid gland. These are triiodothyronine or T3 and thyroxine or T4. These hormones are released following the stimulation of the thyroid gland by thyroid-stimulating hormone or TSH.
TSH is released from the pituitary gland, and it is under the control of thyrotropin-releasing hormone or TRH which is produced in the hypothalamus.
Hypothyroidism can result from a dysfunction in the release of any of these hormones.
Early symptoms of hypothyroidism include fatigue, low heart rate, depression, weight gain and water retention. All of these symptoms are caused by the reduction in basal metabolic rate.
In advanced stages, the symptoms of hypothyroidism are worsened and it can also include goiter, edema, low body temperature, hair loss, impaired memory and skin problems. Because the symptoms of hypothyroidism overlaps with those of vitamin B12 deficiency, experts believe there is a link between both deficiency states.
Many people suffering from hypothyroidism are prescribed thyroid hormone replacement or other thyroid drugs. Of the two thyroid hormones, T3 is widely regarded to be clinically more effective than T4. However, even with T3 replacement, some patients do not fully recover from the symptoms of their deficiency.
Recent clinical data now show that the reason for this is vitamin B12 deficiency.
Vitamin B12 deficiency worsens hypothyroidism. Unfortunately, both deficiencies can go unnoticed and they can be difficult to diagnose.
Some of the symptoms shared by both deficiencies include depression, lethargy, fatigue, disturbed sleep pattern and memory impairment. Where both deficiencies occur, vitamin B12 supplementation must be paired with thyroid hormone replacement or drugs to fully resolve symptoms.
But how often does vitamin B12 deficiency and hypothyroidism affect the same person at the same time? Pretty often as it turns out.
A 2008 study published in The Journal of the Pakistan Medical Association is the most important investigation of the co-occurrence of the two deficiencies. In this study, the researchers evaluated the signs and markers of vitamin B12 deficiency in 116 patients suffering from hypothyroidism.
The results of the study showed a high prevalence of vitamin B12 deficiency among hypothyroid patients.
In this study, as many as 40% of the hypothyroid patients also suffered from vitamin B12 deficiency. The researchers also noted that the classic signs of vitamin B12 deficiency were not good enough for diagnosing this deficiency in hypothyroid patients.
Rather, they recommended the screening of all hypothyroid patients for vitamin B12 deficiency. This should be done through laboratory tests. Where such tests are not available, vitamin B12 supplementation may be added to thyroid hormone replacement or hypothyroidism drugs.
For patients suffering from hypothyroidism, vitamin B12 levels must be close to the upper limit of the acceptable range of vitamin B12 levels in normal patients.
While experts once believed that vitamin B12 deficiency is only common among the elderly because of diminished absorption of the vitamin, the available clinical data show that this deficiency is just as common in the young as it is in older patients. Therefore, measurements of vitamin B12 levels should also be part of the standard treatment protocol in young people suffering from hypothyroidism.
In a 1999 study published in the Annals of Internal Medicine, a group of researchers investigated the link between hypothyroidism and high homocysteine levels.
The study involved 14 hypothyroid patients who were also diagnosed with hyperhomocysteinemia (high levels of homocysteine). Following a few months of treatment with L-thyroxine, the researchers found that the patients’ homocysteine levels fell back to normal values even as their hypothyroidism was resolved.
The researchers concluded that hypothyroidism is a cause of hyperhomocysteinemia and that it is treatable.
Homocysteine is a metabolite of methionine. It is only a temporary metabolite in the synthesis of the amino acid, methionine. For the synthesis to proceeds, vitamin B12 and folate are required.
However, in cases of vitamin B12 and/or folate deficiencies, homocysteine accumulates in the body.
When it accumulates, homocysteine is toxic to the cardiovascular and nervous systems. It has been proven to increase the risk of coronary heart disease and increase the levels of low-density lipoprotein (LDL or “bad” cholesterol).
To prevent its accumulation, folate and vitamin B12 supplements are needed when both or either vitamin is in low supply in the body.
An older study published in the Journal of Clinical Pathology established that thyroid hormones are involved in the syntheses of folate. Since folate and vitamin B12 share a number of biochemical processes, it can also be said that thyroid hormones affect vitamin B12 levels. Therefore, hypothyroidism may lead to vitamin B12 deficiency.
In the 1999 study, the researchers established that patients with primary hypothyroidism usually have high homocysteine levels. Since hypothyroidism is easily treated with thyroid hormones, the damage done to heart and brain by hypothyroidism and vitamin B12 deficiency can be prevented.
Vitamin B12 deficiency can be treated by vitamin B12 supplements. These are available in different forms including pills, sublingual tablets, liquids, nasal spray, dermal patch and injections.
Mild vitamin B12 deficiency can still be treated with dietary sources of the vitamin. Those include lean meat, fish, poultry, eggs, dairy products and fortified cereals.
Hypothyroidism, on the other hand, is treated with thyroxine alone or thyroxine and triiodothyronine.
On the other hand, dietary supplements can be taken to treat hypothyroidism. A good example of such supplements is Thyax.
Thyax will not only treat hypothyroidism but also vitamin B12 deficiency and even hyperhomocysteinemia caused by folic acid deficiency.
It contains all the major B vitamins including B1, B2, B3, B5 B6, B9 and B12.
However, it is folic acid (vitamin B9) and vitamin B12 that are the most important. They are effective for treating anemia, lowering homocysteine levels and reducing the risks of damage to cardiovascular and nervous systems.
In addition, Thyax is effective for treating hypothyroidism. In this regard, it not only prevents vitamin B12 deficiency but also includes iodine sourced from kelp. Since iodine deficiency is the most important cause of hypothyroidism, iodine supplementation, especially from a seafood such as kelp, corrects this thyroid disorder.
Furthermore, Thyax contains amino acids such as acetyl-L-tyrosine and L-phenylalanine, both of which are required for the production of thyroid hormones.
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