Iodine-131 and the pregnant patient

Thyroidal radioactive iodide uptake in the lactating rhesus monkey

Although radioactive iodide uptake (RAIU) is one of the reliable diagnostic methods for thyroid function in adult humans, especially in the diagnosis of thyrotoxicosis, there are limited data for RAIU during pregnancy and lactation in humans and animals. Therefore, we proposed to validate RAIU for the lactating rhesus monkey to further human model studies in thyroid disease. RAIU was performed at 6 and 24 h using 100 µCi of 123I orally in four lactating monkeys. The thyroid and thigh were counted using a scintillation probe and multichannel analyser. A dose/standard ratio of counts/minute was calculated to compensate for background, utilizing differences in the activity between the dose administered and a standard. Thyroidal RAIU varied significantly among monkeys: 6.71 ± 2.40% for the 6 h uptake and 15.44 ± 7.71% for the 24 h uptake. These data showed that the RAIU test may allow a rational clinical approach to thyroid function testing for lactating rhesus monkeys. Additional studies are needed for assessing thyroid function in rhesus monkeys of varying ages and gender with clinical abnormalities.

Chernobyl: relationship between the number of missing newborn boys and the level of radiation in the Czech regions

BACKGROUND

The number of newborn boys was higher than that of girls in the Czech Republic each month from 1950 to 2005. The only exception was November 1986, when the number of newborn boys was significantly reduced. This has been explained by a selective negative impact of the Chernobyl accident in April 1986 on male fetuses during the third month of their prenatal development.

OBJECTIVES

The first and most radioactive cloud passed over the Czech Republic during 30 April-1 May 1986. Concurrent rainfall multiplied the radioactivity by up to > 10,000-fold in specific regions. We verified a hypothesis that the decrease in the male birth fraction in November 1986 correlated with the level of radiation in eight Czech regions after the Chernobyl disaster.

RESULTS

We found a relationship between the level of radiation and the decrease in the number of newborn boys. The number of newborn boys was decreased in the six eastern regions where the radiation was strongly increased due to rain that accompanied the radioactive cloud. In contrast, the number of newborn boys was not reduced in the two western regions where the radioactivity was markedly lower.

CONCLUSIONS

A negative impact of radiation on the prenatal population was manifested as a selective loss of newborn boys in November 1986. This loss correlated with level of radioactivity. The 131I probably played the most important role because of its up-take during primary saturation of fetal thyroid by iodine, which accompanies the onset of the gland function in 3-month-old fetuses.

The Role of Radioactive Iodine in the Treatment of Well-differentiated Thyroid Cancer

The prognosis in differentiated thyroid cancer is excellent. The completeness of thyroidectomy and removal of involved regional metastases are the most important elements of management. Iodine 131 has a role in ablating residual thyroid and treating regional and distant metastases. The effectiveness of the treatment is confirmed by negative follow-up scans and low or undetectable Tg. This therapy is relatively specific, but other tissues can receive meaningful doses of radiation and acute and long-term complications can occur. Therefore, whether the patient will have a better prognosis after treatment with 131I and whether the benefits of treatment are greater than the side effects must be determined for every patient.

[Legal implications of information to the patient in nuclear medicine]

Every patient has the right to be informed about a medical procedure. The nuclear medicine physician has the duty to inform the patients and, if necessary, to obtain a reasonable written consent before some radioisotopic examinations. The following must be considered in every informed consent of a nuclear medicine procedure: the need for the patient information ("why"), the type of information given ("how"), the person who performs it ("who"), the moment in the time ("when") and the place ("where") where the consent is performed. It must always be kept in mind that, although the informed consent has a protection function from the medicolegal point of view, this function may be lost if the consent is not performed correctly. In this paper the importance and the medicolegal implications of the patient information in Nuclear Medicine are evaluated and discussed.

Modern Management of Differentiated Thyroid Cancer

The outcome in differentiated thyroid cancer is excellent. Simple prognostic factors, including the age of the patient at diagnosis, the size of the primary cancer, completeness of surgical excision, and the presence of distant metastases, allow the clinician to judge how a patient will do. The preferred treatment is total thyroidectomy and in selected patients radioactive iodine can be used to ablate residual thyroid or functioning metastases in lymph nodes and distant sites. The physician has two excellent methods for following the patient: the whole-body scan with radionuclides of iodine, and measurement of serum thyroglobulin. In patients with elevated thyroglobulin and negative scans with radioactive iodine, there is increasing evidence that positron emission tomography (PET) is helpful in locating the site of thyroglobulin production.