Recent Publications by CFE Educators

BACKGROUND

Like stable iodine, radioiodines concentrate in the thyroid gland, increasing thyroid cancer risk in exposed children. Data on exposure to the embryonic/fetal thyroid are rare, raising questions about use of iodine 131 (I-131) in pregnant women. We present here estimated risks of thyroid disease from exposure in utero to I-131 fallout from the Chernobyl nuclear accident.

METHODS

We conducted a cross-sectional thyroid screening study (palpation, ultrasound, thyroid hormones, and, if indicated, fine needle aspiration) from 2003 to 2006. Participants were 2582 mother-child pairs from Ukraine in which the mother had been pregnant at the time of the accident on April 26, 1986, or 2 months after the time during which I-131 fallout was still present (1494 from contaminated areas, 1088 in the comparison group). Individual cumulative in utero thyroid dose estimates were derived from estimated I-131 activity in the mother's thyroid (mean 72 mGy; range 0-3230 mGy).

RESULTS

There were seven cases of thyroid carcinoma and one case of Hurthle cell neoplasm identified as a result of the screening. Whereas the estimated excess odds ratio per gray for thyroid carcinoma was elevated (excess odds ratio per gray 11.66), it was not statistically significant (P = 0.12). No radiation risks were identified for other thyroid diseases.

CONCLUSION

Our results suggest that in utero exposure to radioiodines may have increased the risk of thyroid carcinoma approximately 20 yr after the Chernobyl accident, supporting a conservative approach to medical uses of I-131 during pregnancy.

BACKGROUND

Intraoperative parathyroid hormone (IOPTH) measurement is used to confirm biochemical cure during parathyroidectomy. Falsely decreased IOPTH measurements could result in false-negative or false-positive results and lead to failed parathyroidectomy or unnecessary additional exploration.

STUDY DESIGN

The records of all patients who underwent parathyroidectomy with IOPTH between May and August 2007 were retrospectively reviewed, and the frequency of hemolysis of IOPTH samples was determined. Separately, 10 split-samples were hemolyzed using the freeze-thaw technique.

RESULTS

Forty-seven patients underwent parathyroidectomy, and 226 IOPTH samples were sent. Seventeen (7.5%) specimens from 9 (18.8%) patients were hemolyzed. In 8 split-samples, the range of decrease caused by hemolysis was 24.5% to 53.8% compared with nonhemolyzed controls.

CONCLUSIONS

Hemolysis of IOPTH samples occurs commonly and falsely decreases IOPTH levels. Unrecognized hemolysis in pre-excision specimens could result in false-negative IOPTH results and lead to unnecessary continued exploration. Unrecognized hemolysis in postexcision specimens could lead to false-positive IOPTH results and lead to failed parathyroidectomy and the need for reoperation. Thus, hemolysis may be an easily preventable cause of erroneous IOPTH measurements.

PURPOSE

Given that the prevalence of childhood obesity is increasing in the United States, we tested the timely hypothesis that obesity hinders physical examination based localization of the cryptorchid testis.

MATERIALS AND METHODS

Body mass index and percentiles of weight for height and body mass index for age were calculated for boys undergoing surgery for cryptorchidism at the University of California San Francisco Children's Hospital and Children's Hospital of Oakland. Two definitions of obesity were examined, ie greater than 85% or greater than 95% for either percentile. Patients were examined in the office and under general anesthesia before the skin incision. Intraoperative testicular location was recorded for each patient. The numbers of correct and incorrect preoperative determinations of testicular location were stratified by weight classification. Results were analyzed using contingency tables and Fisher's exact test.

RESULTS

A total of 161 boys were recruited, accounting for 171 testes. The predictive value of palpating a suspected testis preoperatively with patients under anesthesia was greater than 95% for all weight classifications (p 0.0001). The predictive value of not palpating a testis preoperatively under anesthesia was greater than 56% for obese boys and greater than 42% for nonobese boys (p 0.0001). The concordance rates between examinations in the office and those performed under anesthesia were 90.9% and 82.7% for obese and nonobese boys, respectively (p = 0.51). The predictive value of not palpating a suspected cryptorchid testis in the office was higher in nonobese boys than in obese boys (81% vs 22%, p 0.0001).

CONCLUSIONS

In our series childhood obesity did not make preoperative testicular examinations under anesthesia less accurate. However, office examinations may be more accurate in nonobese boys.

BACKGROUND

Hypothyroidism is the most common thyroid abnormality in patients treated with high doses of iodine-131 (131I). Data on risk of hypothyroidism from low to moderate 131I thyroid doses are limited and inconsistent.

OBJECTIVE

This study was conducted to quantify the risk of hypothyroidism prevalence in relation to 131I doses received because of the Chornobyl accident.

METHODS

This is a cross-sectional (1998-2000) screening study of thyroid diseases in a cohort of 11,853 individuals 18 years of age at the time of the accident, with individual thyroid radioactivity measurements taken within 2 months of the accident. We measured thyroid-stimulating hormone (TSH), free thyroxine, and antibodies to thyroid peroxidase (ATPO) in serum.

RESULTS

Mean age at examination of the analysis cohort was 21.6 years (range, 12.2-32.5 years), with 49% females. Mean 131I thyroid dose was 0.79 Gy (range, 0-40.7 Gy). There were 719 cases with hypothyroidism (TSH > 4 mIU/L), including 14 with overt hypothyroidism. We found a significant, small association between (131)I thyroid doses and prevalent hypothyroidism, with the excess odds ratio (EOR) per gray of 0.10 (95% confidence interval, 0.03-0.21). EOR per gray was higher in individuals with ATPO or = 60 U/mL compared with individuals with ATPO > 60 U/mL (p 0.001).

CONCLUSIONS

This is the first study to find a significant relationship between prevalence of hypothyroidism and individual (131)I thyroid doses due to environmental exposure. The radiation increase in hypothyroidism was small (10% per Gy) and limited largely to subclinical hypothyroidism. Prospective data are needed to evaluate the dynamics of radiation-related hypothyroidism and clarify the role of antithyroid antibodies.