Endocrine effects of Fukushima: Radiation-induced endocrinopathy Asfandyar Khan Niazi and Shaharyar Khan Niazi1

Quote from Indian Journal of Endocrinology and Metabolism,
Indian J Endocrinol Metab. 2011 Apr-Jun; 15(2): 91–95.
doi: 10.4103/2230-8210.81936
PMCID: PMC3125012
Endocrine effects of Fukushima: Radiation-induced endocrinopathy
Asfandyar Khan Niazi and Shaharyar Khan Niazi1

This article has been cited by other articles in PMC.
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Abstract

The unfortunate accidents of Chernobyl and Fukushima have led to an enormous amount of radioactive material being released into the atmosphere. Radiation exposure to the human body may be as a result of accidents, such as those in Chernobyl and Fukushima, or due to occupational hazards, such as in the employees of nuclear plants, or due to therapeutic or diagnostic procedures. These different sources of radiations may affect the human body as a whole or may cause localized damage to a certain area of the body, depending upon the extent and dosage of the irradiation. More or less every organ is affected by radiation exposure. Some require a higher dose to be affected while others may be affected at a lower dose. All the endocrine glands are susceptible to damage by radiation exposure; however, pituitary, thyroid and gonads are most likely to be affected. In addition to the endocrine effects, the rates of birth defects and carcinomas may also be increased in the population exposed to excessive radiation.
Keywords: Chernobyl, Fukushima, nuclear accidents, radiation exposure, radiation-induced endocrinopathy
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INTRODUCTION

A devastating tsunami, caused by a violent earthquake of 8.9-Richter magnitude, struck the coastal areas of Japan on March 11, 2011. It caused extensive damage to life, property and infrastructure in the affected areas. The earthquake also damaged a nuclear installation located in Fukushima, leading to increased pressure and radiation levels in the reactor. Even after concerted efforts by the Japanese authorities, a large amount of radiation and radioactive material was released into the environment. The release of this radioactive material into the environment has created genuine concern among the medical community.

This unfortunate incident in Japan has brought back memories of a similar nuclear accident which occurred on April 26, 1986, in Chernobyl. A very large amount of radioactive iodine-131 (I131) and lesser amounts of short-lived iodine isotopes (iodine-129 and iodine-132 through iodine-135) were released intermittently over a period of 10 days after the accident. A large population was exposed to ionizing radiation, mostly from ingestion of radioiodine-contaminated food (particularly milk in children) and/or inhalation of radioactive isotopes dispersed in the environment.[1] This immense radiation exposure affected not only Ukraine, but also many neighboring countries. The effects of the unfortunate incident are still being seen in the affected areas.

Similar effects are expected to be seen after the radiation exposure in Fukushima. Even though the level of radiation exposure in Fukushima does not match that of Chernobyl, it should be remembered that the situation in Fukushima is potentially worse since a major metropolis of 30 million people is close by.

This time, however, the medical community needs to be better prepared to handle the consequences of such a huge radiation exposure to a large population.
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EFFECTS OF THE RADIATION EXPOSURE IN CHERNOBYL

A few years after the nuclear accident in Chernobyl, a significant increase in the incidence of childhood thyroid carcinomas and autoimmune thyroid disease was observed. This was found to be associated with the excessive radiation exposure.[2,3] People living in Chernobyl and adjacent affected areas were seen to have 50% lower sympathetic activity, 36% lower adrenal cortical activity and significantly lower blood cortisol levels. They also exhibited increased hypophyseal-thyroid system dysfunction, higher incidence of goiter and thyroiditis. An increased rate of secretion of gonadotropic hormones and accelerated sexual development in females was noted. Higher rates of congenital diabetes were also seen. Higher concentrations of thyroxine-binding globulin, lower concentrations of free T3, and increased risk of non-toxic single nodular and multinodular goiters have been reported.[4] Higher levels of prolactin and renin, with lower progesterone levels,[5] have been documented.

This has led to continuous, chronic morbidity, even though the initial radiation exposure has passed long since. Children with congenital anomalies still continue to be born in the affected areas. A large number of mental and physical anomalies were seen in the children born soon after the accident.[6] Down’s syndrome, neural tube defects, chromosomal abnormalities, cardiovascular diseases, immunologic disorders, lens changes, cancer, mental retardation, thyroid diseases and leukemias were some of the more frequent problems seen in the children from affected areas.[7]

One hopes that such a situation will not be repeated in Japan.
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PATHOPHYSIOLOGY OF RADIATION-INDUCED DAMAGE

The harmful effects of ionizing radiation, especially its carcinogenic potential, are fairly well known. Ionizing radiations above a threshold level, which varies for each organ, lead to tissue destruction. However, even at levels below the threshold level, damage can occur to functional and structural proteins in the cells, including DNA and RNA.

In addition to burns and radiation sickness which may themselves lead to immediate death, there are some delayed effects of a high-dose radiation exposure as well. The delayed effects cause most damage to the rapidly dividing cells of the body and to those cells which have an inherent ability to concentrate the radioactive materials. An example of the latter includes the thyroid gland, which concentrates radioactive iodine. Due to the rapid cell division and growth in fetuses, they form a group more prone to be affected by radiation exposure. This is consistent with the morbidity pattern seen after Chernobyl.
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OTHER TYPES OF RADIATION EXPOSURE

Ultraviolet radiation (UVR) whether of solar or artificial origin, is a known carcinogen. Excessive exposure to UVR increases the risk of several types of cancer, cortical cataract, some conjunctival neoplasms, ocular melanoma, autoimmune and viral diseases.[8]

Iatrogenic radiation exposure, for diagnostic or therapeutic purposes, holds the same risks as does environmental radiation exposure. However, a key difference is that in most iatrogenic cases the radiation exposure is focused and concentrated on a specific region of the body. Although the radiation exposure involved in this case may be less, repeated exposure may lead to considerable tissue damage.

Although diagnostic imaging such as X-rays and computed tomography (CT) scans provide great benefits, their use is associated with small increases in cancer risk.[9] Similarly, mammography, although very useful, is associated with the amount of radiation that an ordinary person would be exposed to over a 3-month period.

Exposure to diagnostic radiography in utero has been associated with increased risk of childhood cancer, particularly leukemia.[10] Radiation is a well-known etiology for many central nervous system (CNS) tumors as well especially meningiomas, sarcomas and gliomas.[11]
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ENDOCRINE EFFECTS OF RADIATION EXPOSURE

Radiation exposure affects virtually every endocrine gland, but to different degrees. While some glands such as pituitary, thyroid and gonads are sensitive to radiation, the adrenal is extremely resistant.
Pituitary

The risk of developing pituitary tumors after exposure to ionizing radiation is increased. Even small doses (i.e. Literature > PubMed Central (PMC)
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