In March 2011, when a nuclear leak occurred in Japan, the Chinese people were introduced to another chemical term, iodine-131, which caused panic and a salt rush. However, Zhou Bing, sitting in the waiting room of the Department of Nuclear Medicine at Zhongshan Second Hospital, told reporters, “Iodine-131 is my ‘life-saver'”. Three years ago, 25-year-old Zhou Bing was diagnosed with hyperthyroidism and began a protracted treatment. The local doctor told her she had to take the medication for at least two years and that she could not get pregnant during that time. However, two years later, her symptoms were still recurring. In her desperation, she heard about iodine-131 therapy, an internal radiation treatment. “Although it sounded a little scary, I couldn’t afford to lose any more time or money,” Zhou said. It turned out that Zhou Bing’s bet was right, and she was really cured! Now, six months later, she came to the hospital for a review and to consult about pregnancy. 28-year-old Zhou Bing is extremely eager to have a baby. Sniping hyperthyroidism and nail cancer Iodine-131, a radioactive isotope, has 78 neutrons in its nucleus, four more than the nucleus of stable iodine. In layman’s terms, the atomic weight of iodine-131 is heavier than that of ordinary iodine. Therefore, iodine-131 decays and during the decay process emits gamma and beta rays (99% of the total number of rays). beta rays have a short range, averaging about 1 mm and up to 2 mm, and are capable of destroying thyroid tissue, but have little effect on surrounding tissues. This is the reason why people panic about it, and this is the root of its cure. When it comes to snipers, people have the image of being precise, aiming at the target and killing it with one shot. Iodine-131 is exactly like the shot sent by the sniper, which hits the thyroid gland in the neck. After a patient takes iodine-131 orally, the vast majority of it collects in the thyroid gland, except for a small amount that is excreted from the body, and its concentration can reach 25 times the plasma concentration. “The main indications for iodine-131 are Graves’ hyperthyroidism and differentiated thyroid cancer,” said Professor Jiang Ningyi. There are several types of hyperthyroidism, but the most common one is Graves’ hyperthyroidism, i.e. diffuse goiter with hyperthyroidism, which accounts for almost 80% of all the subtypes. Zhou Bing has Graves’ hyperthyroidism, and her hyperthyroid symptoms have largely disappeared after taking only one dose of iodine-131. “Some hyperthyroid patients, depending on their individual circumstances, may need to take 2 doses, or multiple doses. But, basically, they can get rid of their hyperthyroidism”, said Jiang Ningyi. In addition to Graves’ hyperthyroidism, another indication for iodine-131 is differentiated thyroid cancer. While thyroid cancer has many types, differentiated thyroid cancer accounts for almost 90 percent of the cases. “The first thing is to remove the thyroid cancer surgically, the cleaner the cut the better; secondly, to clear the residual thyroid tissue by oral iodine-131.” Jiang Ningyi said. Sitting next to Zhou Bing, Ms. Li, who was also waiting for a review, was both a former nail cancer patient. She pulled down the silk scarf around her neck, and we saw a clear scar. Hypothyroidism: Americans look on the bright side After Ms. Li’s surgery to remove her thyroid gland and clear the residual tissue with iodine-131, the main task left is to take thyroid hormone tablets (i.e., replacement therapy) to maintain thyroid hormone levels at normal levels and beware of hypothyroidism is enough. This was a completely trivial task for Ms. Li, who had recovered from cancer. But again, Bing Zhou had a little complaint about the replacement therapy. It is true that some hyperthyroid patients recovered after taking Iodine-131, while Zhou Bing developed hypothyroidism 2 months after taking Iodine-131. She came for a review this time and wanted to find out when she could stop the replacement therapy. The possibility of stopping the medication involves another question that concerns many people: Is hypothyroidism sure to occur after iodine-131 treatment? “It depends on the individual and cannot be generalized,” says Jiang Ningyi. ”Getting hyperthyroidism cured, but without hypothyroidism, is the outcome that all nuclear medicine doctors would like to see. But in reality, it’s too difficult to do that.” Jiang Ningyi spoke. Because each patient has a different sensitivity to iodine-131, even if two people with the exact same condition are treated with the same dose of iodine-131, the end result may be different, with someone cured and someone hypothyroid. Americans tend to be more open-minded when it comes to hypothyroidism. Their principle is that they would rather take a little more Iodine-131 to cure their hyperthyroidism than worry about hypothyroidism. The reason is that hypothyroidism is simple to treat, and oral thyroid hormone tablets will take care of it. Americans don’t think it’s a big deal to take an extra pill every day. ”Therefore, the dose of iodine-131 used by American doctors is often on the high side; the probability of hypothyroidism occurring after a patient takes the drug is also much higher than in China.” Jiang Ningyi describes. The occurrence of hypothyroidism within 1 year of iodine-131 treatment is called early-onset hypothyroidism. Some patients with early-onset hypothyroidism sometimes only need to take thyroid hormone for a period of time before they can stop taking it. “It may be due to certain thyroid cells being dazed by a stick and temporarily suppressed and slowed down to return to normal.” Jiang Ningyi explained. And hypothyroidism that occurs after 1 year is called advanced hypothyroidism or permanent hypothyroidism. At this point, thyroid hormone replacement therapy must be administered and is a lifelong treatment. Therefore, Zhou Bing needs to be observed and monitored for a period of time to determine whether she needs to take thyroid hormone for life. After iodine 131 treatment is administered, routine follow-up examinations must be performed to evaluate the effectiveness of the treatment. Usually, this is done by returning to the hospital at 1 month, 3 months, or 6 months after taking iodine 131; if things are normal, then after 6 months; and if they are still normal, then annually thereafter. At the same time, during this period, once the symptoms of hypothyroidism such as fear of cold, slow reaction, not wanting to move, gaining weight, etc. must be promptly reviewed in the hospital. Six months later 28-year-old Zhou Bing wants to be a mother, although not quite sure, but still have a little spectrum in mind. Because from time to time, there are big bellies in the waiting room, that is the mothers-to-be who come for review after being cured of hyperthyroidism. But she still hoped her doctor could give her a definite answer. “First of all, iodine-131 does not affect reproductive function”, Jiang Ningyi said with certainty. This is because iodine-131 does not enter reproductive organs such as the uterus, ovaries and testicles at all. In addition, the physical half-life of iodine-131 is 8 days, while the biological half-life in human body is 3 to 5 days due to the influence of metabolism. This means that after roughly 40 days, the amount of iodine-131 in the human body is minimal. ”However, to try to avoid affecting the fetus, it is best to consider pregnancy after six months of taking iodine-131.” Jiang Ningyi talked about. And such a view has already reached a consensus among nuclear medicine specialists. However, one obligation that women cannot avoid after pregnancy is the review. Pregnant women need to go to the hospital every month for a follow-up check to monitor their thyroid hormone levels. This is because, after pregnancy, all physiological processes in a woman’s body may change, and the thyroid gland is no exception. In case of mild hypothyroidism, the pregnant woman herself may not feel it, but it may affect the fetal development. For those mothers who feel uncomfortable and experience symptoms of hypothyroidism such as slow response and fear of cold, it is important to go to the hospital in time for examination. For pregnant women with serious conditions, they need to be checked once every half month. However, in real life there are always mothers-to-be who are too busy to take time for regular checkups. Jiang Ningyi’s advice is: the first trimester and the second trimester should not be missed in any case. Because, the first trimester is a critical period for the formation of fetal organs; and the second trimester is close to delivery and must be ensured to be normal in all aspects. In the case of low thyroid hormone levels during the examination, pregnant women need to be properly treated with alternative treatment under the guidance of the doctor to ensure the healthy growth of the fetus.