Thursday, December 17, 2009

Excess iodine can cause hypothyroidism

Iodine, although in the human body requires only 20-50 mg, and only as much as a tablespoon, but it is closely related with people's lives. Human body, 70% to 80% of the iodine concentration in the thyroid body, constitutes an important component of thyroid hormone and the rest distributed in the circulating blood. Thyroid hormone can regulate the body's energy metabolism and oxygen in the process of phosphorylation involved in the synthesis of the three major nutrients, heat production and decomposition processes, promote the body's growth and development.

Iodine in the human body has 80-90% from food, absorbed through the intestinal tract, in the extracellular free, and then quickly capture most of thyroid gland, a small part with the saliva, urine and sweat to escape along with other in vitro.

Iodine deficiency is congenitally deficient

Under normal circumstances, the body reserves of iodine can be 2 months old, in the early iodine deficiency, iodine reserves, and the body can still be a strong regulatory mechanism to ensure proper functioning of thyroid gland. After a long-term iodine deficiency, can not make bricks without straw, synthetic thyroid hormone is increasingly difficult, eventually leading to the health of balance, a series of barriers, collectively referred to as iodine deficiency disorders (IDD).

People commonly known as the "big neck disease" is also a kind of iodine deficiency disorders. Under normal circumstances, thyroid tissue according to the body's demand for thyroid hormones in the operation, when the body's thyroid hormone requirements increase, the thyroid follicular cells in the active state, microglia reduced, epithelial cells larger. Iodine deficiency, due to lack of raw materials for synthesis of thyroid hormone, thyroid hormone synthesis less.

At this time control of the hypothalamic-pituitary-thyroid gland to begin secreting thyroid-stimulating hormone to urge the active thyroid cells to meet the needs of the body's thyroid hormone. As a result, the beginning of thyroid cell proliferation, larger, long run to form a swollen "big neck."

Addition of iodine can not be ignored but also because it is a critical moment in the brain play a role in development. On brain development period, the regulation of thyroid hormone is the main factor responsible for promoting neuronal proliferation, migration, differentiation, and functional. Iodine deficiency, thyroid hormone reduced, can lead to brain growth retardation, brain weight, reduced gyrus, cerebral cortex thinning and so on, resulting in lower IQ children.

Iodine excess lead to hypothyroidism

In the world things are going too far, and iodine excess and iodine deficiency are similar, can cause decreased thyroid function. In 2008, Tianjin Medical University ZHONG Na Sang six post-graduate students and other adults, the safety of iodine intake of clinical trials carried out in 4 weeks, the researchers will be 161 normal healthy thyroid function is divided into 7 groups, respectively, per day taking 500-2000 micrograms of iodine ranging.

Because of excessive iodine can be excreted with the urine, in the experiment has been under the weight of urine iodine, the researchers will be able to determine the demand for iodine in the body. Through the blood and urine, Tianjin Medical University, researchers found that iodine outset, each group of people of urinary iodine levels were significantly increased, serum thyroid-stimulating hormone significantly increased, reaching normal levels of 1 to 2 times, but the thyroid gland is still working , 2 weeks later, it began to appear with subclinical hypothyroidism.

In fact, the thyroid iodine intake for the strict control mechanisms to prevent damage caused by iodine on the human body. At home and abroad in recent years, studies have confirmed that thyroid cells for the uptake of iodine by the sodium - iodine transport body (NIS) control, NIS is a glycosylated membrane protein, in the body is the role of porters is mainly responsible for running from the blood to the thyroid cells send iodine, so that the intracellular iodine concentration 20-40 times higher than outside the cell, when the body of excessive iodine intake, the body will inhibit NIS generated, thus reducing the uptake of iodine.

In addition, the physiological function of the thyroid gland by the brain and thyroid gland while the dual regulation, the brain through the hypothalamic-pituitary secretion of thyroid-stimulating hormone to regulate thyroid activity and thyroid Youxiang feedback from the brain's own needs, this mechanism guarantees a certain extent, the body under the physiological needs iodine intake.

Since the body has a self-adjustment function, then the excess of iodine is caused by thyroid gland injury how does?

Although iodine excess does not make the body content of iodine doubled, but if the iodine status persists, in order to protect the body from injury, sodium - iodine transport body (NIS) will continue at a low level, a large number of iodine can not be used, eventually ruled out as urine. Over time, reduced iodine content in thyroid tissue, and thyroid hormones have also been reduced. At this time, in order to maintain the normal operation of thyroid gland, the body also increases the content of NIS to increase the supply of iodine. As a result, the body in self-regulation and inhibition of iodine fiddle around with, eventually an exception occurs, causing thyroid damage, causing goiter and other adverse reactions.

The complications of high doses

Lack of Han Chinese people know how to Chisha, Chisha fill Han, so a large-scale iodine supplement policy after the year 2000, iodine-deficiency diseases are the basic control.

May be surprising is that the emergence of iodine deficiency has been a series of iodine complications. Is it related to consumption of iodized salt level? Now there is no conclusion, but the medical profession generally believe that iodine supplementation does cause some side effects, for long-term iodine deficiency in thyroid cells, the sudden iodine, is not a savior, but a killer.

As early as 1983, scholars, Many MC was found in animal experiments, once the excess iodine being oxidized, organic-based, you may have on the toxicity of iodine deficiency in thyroid cells. 2003, Tianjin Medical University, Luo Yuyu master a set of animal experiments, on the implementation of iodine deficiency in mice 5 times to 50 times the physiological reagents of iodine intake results show that iodine deficiency has been for some time for the mice who If the enlargement of the thyroid gland suddenly exposed to high doses of iodine in front, may induce thyroid follicular epithelial cell necrosis.

Compared with mice, who naturally have a stronger ability to adapt to the environment, people in long-term iodine deficiency, the thyroid tissue "will be from outside the military command," the formation of functional autonomy of thyroid nodules, is no longer obey the orders of the brain , and according to manufacture as much as possible reserves of iodine thyroid hormone. This time, the sudden nature of iodine, the body will be health too much thyroid hormone. This symptom in medicine become "iodine hyperthyroidism (IIH)", is the most common complication of an iodine supplementation. In addition, there are the more common autoimmune thyroid disease.

Internationally recognized research shows iodine, iodine intake and thyroid disease, the relationship into a U-shaped relationship between the iodine intake is too high and too low will lead to an increase in thyroid diseases. WHO believes that population levels of urinary iodine 100 to 200 micrograms of iodine per liter is the most appropriate state, in this state, iodine deficiency disease and iodine is the lowest incidence of diseases, while more than 300 micrograms per liter were considered to be excessive iodine intake. 150 micrograms / daily intake was considered more appropriate.

To do a lot more than just good, right, everyone is a quite difficult challenge, after all, eat and drink can not be moved from the restaurant lab bar to holding a graduated cylinder cup.

Iodized salt, who needs? How much to eat?

Southern Weekly reporter is a single Chongshan order

From ten years ago, universal love of iodine, and today there are individuals who stand up and refuse to iodized salt, it is to treat these daily intake of iodine in micrograms per meter elements, from one extreme to another extreme. To find out who should not eat iodized salt, this is a complex issue.

A non-iodine-deficient area residents need not consume iodized salt. A number of areas such as in Shandong Heze Prefecture, part of iodine areas, has been abolished mandatory iodine; there eating seafood-based fishermen, it has been calculated daily intake of more than 750 grams of marine fish populations, they do not need to iodine supplementation of.

Two patients with hyperthyroidism without consumption of iodized salt, because iodine will increase the synthesis of thyroid hormones, exacerbating illness.

3 thyroiditis (Hashimoto's Disease) patients not to consume iodized salt, iodine supplementation may increase the inflammatory symptoms.

Four patients with thyroid tumors, thyroid cancer and on the relationship between the level of iodine nutrition, the current medical research is not clear. Therefore, in patients with thyroid cancer in a matter of consumption of iodized salt in more cautiously in light condition, follow doctor's orders was supreme.

Five patients with hypothyroidism (hypothyroidism), the need for such groups make up points, there are also controversial, as a causal factor in hypothyroidism are diverse and can not be generalized.

6 other thyroid disorders, usually believed that only goiter patients need iodine, but in fact can be induced by iodine deficiency and iodine excess thyroid disease, so it is still necessary to integrate the illness and their iodine nutrition status, under the guidance of a doctor to do out of choice.

7 with thyroid disease, pregnant and lactating women, this is a difficult question, iodine nutrition level and the level of intellectual development of infants and young children closely related to the need to comply with doctor's orders with the individual circumstances, or take a separate pairs of breast-feeding infants and young children method of iodine supplementation.

1 comment:

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