Robert J. McConnell

I-131 dose response for incident thyroid cancers in Ukraine related to the Chornobyl accident.

Background: Current knowledge about Chornobyl-related thyroid cancer risks comes from ecological studies based on grouped doses, case–control studies, and studies of prevalent cancers. Objective: To address this limitation, we evaluated the dose–response relationship for incident thyroid cancers using measurement-based individual iodine-131 (I-131) thyroid dose estimates in a prospective analytic cohort study. Methods: The cohort consists of individuals < 18 years of age on 26 April 1986 who resided in three contaminated oblasts (states) of Ukraine and underwent up to four thyroid screening examinations between 1998 and 2007 (n = 12,514). Thyroid doses of I-131 were estimated based on individual radioactivity measurements taken within 2 months after the accident, environmental transport models, and interview data. Excess radiation risks were estimated using Poisson regression models. Results: Sixty-five incident thyroid cancers were diagnosed during the second through fourth screenings and 73,004 person-years (PY) of observation. The dose–response relationship was consistent with linearity on relative and absolute scales, although the excess relative risk (ERR) model described data better than did the excess absolute risk (EAR) model. The ERR per gray was 1.91 [95% confidence interval (CI), 0.43–6.34], and the EAR per 104 PY/Gy was 2.21 (95% CI, 0.04–5.78). The ERR per gray varied significantly by oblast of residence but not by time since exposure, use of iodine prophylaxis, iodine status, sex, age, or tumor size. Conclusions: I-131–related thyroid cancer risks persisted for two decades after exposure, with no evidence of decrease during the observation period. The radiation risks, although smaller, are compatible with those of retrospective and ecological post-Chornobyl studies.

Thyroid cancer risk in Belarus among children and adolescents exposed to radioiodine after the Chornobyl accident

Background:Previous studies showed an increased risk of thyroid cancer among children and adolescents exposed to radioactive iodines released after the Chornobyl (Chernobyl) accident, but the effects of screening, iodine deficiency, age at exposure and other factors on the dose–response are poorly understood.Methods:We screened 11 970 individuals in Belarus aged 18 years or younger at the time of the accident who had estimated 131I thyroid doses based on individual thyroid activity measurements and dosimetric data from questionnaires. The excess odds ratio per gray (EOR/Gy) was modelled using linear and linear–exponential functions.Results:For thyroid doses <5 Gy, the dose–response was linear (n=85; EOR/Gy=2.15, 95% confidence interval: 0.81–5.47), but at higher doses the excess risk fell. The EOR/Gy was significantly increased among those with prior or screening-detected diffuse goiter, and larger for men than women, and for persons exposed before age 5 than those exposed between 5 and 18 years, although not statistically significant. A somewhat higher EOR/Gy was estimated for validated pre-screening cases.Conclusion:10–15 years after the Chornobyl accident, thyroid cancer risk was significantly increased among individuals exposed to fallout as children or adolescents, but the risk appeared to be lower than in other Chornobyl studies and studies of childhood external irradiation.

Defects of taste and smell in patients with hypothyroidism

Taste and smell functions were measured in 18 unselected patients with untreated primary hypothyroidism, and in 15 of the 18 patients after treatment with thyroid hormones. Before treatment, 9 of the 18 patients (50 per cent) were aware of some alteration in their sense of taste, and 7 of the 18 patients (39 per cent) were aware of some alteration in their sense of smell. Distoritions of tase (dysgeusia) and smell (dysosmia) were frequent complaints among the untreated patients; dysgeusia was observed by 7 patients (39 per cent) and dysosmia by 3 patients (17 per cent). Median detection and recognition thresholds for four taste stimuli salt (sodium chloride), sweet (sucrose), sour (hydrochloric acid) and bitter (urea), and for two smell stimuli (pyridine and nitrobenzene), were determined in each patient before and after treatment with thyroid hormones. Before treatment, decreased taste acuity (hypogeusia) for at least one stimulus was observed in 14 of the patients (83 per cent); the most common abnormalities were in the detection and recognition of bitter stimuli. Median detection thresholds for both smell stimuli were also markedly elevated (hyposmia) before therapy. Treatment with throid hormones largely reversed both the taste and smell defects. In one patient, taste and smell abnormalities were completely corrected after 16 days of treatment with thyroxine. This study indicates that taste and smell defects are common clinical abnormalities in primary hypothyroidism, and suggests that these defects may contribute to the anorexia and lack of interest in eating which are frequently observed.

A Cohort Study of Thyroid Cancer and Other Thyroid Diseases after the Chornobyl Accident: Objectives, Design and Methods

Abstract Chornobyl Thyroid Diseases Study Group of Belarus, Ukraine, and the USA. A Cohort Study of Thyroid Cancer and Other Thyroid Diseases after the Chornobyl Accident: Objectives, Design and Methods. Radiat. Res. 161, 481–492 (2004). The thyroid gland in children is one of the organs that is most sensitive to external exposure to X and γ rays. However, data on the risk of thyroid cancer in children after exposure to radioactive iodines are sparse. The Chornobyl accident in Ukraine in 1986 led to the exposure of large populations to radioactive iodines, particularly 131I. This paper describes an ongoing cohort study being conducted in Belarus and Ukraine that includes 25,161 subjects under the age of 18 years in 1986 who are being screened for thyroid diseases every 2 years. Individual thyroid doses are being estimated for all study subjects based on measurement of the radioactivity of the thyroid gland made in 1986 together with a radioecological model and interview data. Approximately 100 histologically confirmed thyroid cancers were detected as a consequence of the first round of screening. The data will enable fitting appropriate dose–response models, which are important in both radiation epidemiology and public health for prediction of risks from exposure to radioactive iodines from medical sources and any future nuclear accidents. Plans are to continue to follow-up the cohort for at least three screening cycles, which will lead to more precise estimates of risk.

A cohort study of thyroid cancer and other thyroid diseases after the Chornobyl accident: pathology analysis of thyroid cancer cases in Ukraine detected during the first screening (1998-2000).

The Ukrainian American Cohort Study evaluated the risk of thyroid disorders in a group of individuals who were younger than age 18 years at the time of the Chornobyl (Chernobyl) accident. In this article, the authors describe the pathology of thyroid carcinomas detected in the first screening.

The use of microabrasion to remove discolored enamel: a clinical report.

There is an ever-growing demand for esthetic dental treatment. Treatment modalities include crowns, bleaching, and ceramic or composite veneers. A more conservative treatment option, enamel microabrasion, may be indicated in certain clinical scenarios. The purpose of this clinical report is to describe the use of enamel microabrasion for a patient with discolored anterior teeth.

Bond strengths of two ceramic brackets using argon laser, light, and chemically cured resin systems.

The present study compared tooth-bracket bond strengths using two types of ceramic brackets and three methods of polymerization: argon laser, conventional light, and chemical. Ninety extracted human premolars were prepared for bonding with pumice and gel etchant. Using single crystal alumina brackets with silanated bases, three groups of 15 teeth were bonded with one of the three polymerization methods. Similarly, three groups of 15 teeth were bonded with polycrystal alumina brackets with nonsilanated bases. Each bonded bracket was tested on an Instron tensile testing machine in shear mode to determine shear debonding strength. Fracture sites were recorded. Results demonstrated that (1) all combinations produced shear bond strengths greater than those considered clinically acceptable, (2) the mean shear bond strengths of the single crystal alumina brackets with silanated bases were significantly higher than those of the polycrystal alumina brackets with nonsilanated bases, and (3) no enamel fractures were found on debonding the chemically cured brackets while the light and laser groups exhibited a 10% rate of enamel fracture on debonding.

Measures of Thyroid Function among Belarusian Children and Adolescents Exposed to Iodine-131 from the Accident at the Chernobyl Nuclear Plant

Background: Thyroid dysfunction after exposure to low or moderate doses of radioactive iodine-131 (131I) at a young age is a public health concern. However, quantitative data are sparse concerning 131I-related risk of these common diseases. Objective: Our goal was to assess the prevalence of thyroid dysfunction in association with 131I exposure during childhood (≤ 18 years) due to fallout from the Chernobyl accident. Methods: We conducted a cross-sectional analysis of hypothyroidism, hyperthyroidism, autoimmune thyroiditis (AIT), serum concentrations of thyroid-stimulating hormone (TSH), and autoantibodies to thyroperoxidase (ATPO) in relation to measurement-based 131I dose estimates in a Belarusian cohort of 10,827 individuals screened for various thyroid diseases. Results: Mean age at exposure (± SD) was 8.2 ± 5.0 years. Mean (median) estimated 131I thyroid dose was 0.54 (0.23) Gy (range, 0.001–26.6 Gy). We found significant positive associations of 131I dose with hypothyroidism (mainly subclinical and antibody-negative) and serum TSH concentration. The excess odds ratio per 1 Gy for hypothyroidism was 0.34 (95% CI: 0.15, 0.62) and varied significantly by age at exposure and at examination, presence of goiter, and urban/rural residency. We found no evidence of positive associations with antibody-positive hypothyroidism, hyperthyroidism, AIT, or elevated ATPO. Conclusions: The association between 131I dose and hypothyroidism in the Belarusian cohort is consistent with that previously reported for a Ukrainian cohort and strengthens evidence of the effect of environmental 131I exposure during childhood on hypothyroidism, but not other thyroid outcomes.

Analysis of thyroid malignant pathologic findings identified during 3 rounds of screening (1997-2008) of a cohort of children and adolescents from belarus exposed to radioiodines after the Chernobyl accident.

Recent studies of children and adolescents who were exposed to radioactive iodine‐131 (I‐131) after the 1986 Chernobyl nuclear accident in Ukraine exhibited a significant dose‐related increase in the risk of thyroid cancer, but the association of radiation doses with tumor histologic and morphologic features is not clear.

Thyroid cancer in Ukraine after the Chernobyl accident (in the framework of the Ukraine-US Thyroid Project).

As a result of the accident at the Chernobyl Nuclear Power Plant, millions of residents of Belarus, Russia, and Ukraine were exposed to large doses of radioactive iodine isotopes, mainly I-131. The purpose of the Ukraine-American (UkrAm) and Belarus-American (BelAm) projects are to quantify the risks of thyroid cancer in the framework of a classical cohort study, comprising subjects who were aged under 18 years at the time of the accident, had direct measurements of thyroid I-131 radioactivity taken within two months after the accident, and were residents of three heavily contaminated northern regions of Ukraine (Zhitomir, Kiev, and Chernigov regions). Four two-year screening examination cycles were implemented from 1998 until 2007 to study the risks associated with thyroid cancer due to the iodine exposure caused during the Chernobyl accident. A standardised procedure of clinical examinations included: thyroid palpation, ultrasound examination, blood collection followed by a determination of thyroid hormone levels, urinary iodine content test, and fine-needle aspiration if required. Among the 110 cases of thyroid cancer diagnosed in UkrAm as the result of four screening examinations, 104 cases (94.5%) of papillary carcinomas, five cases (4.6%) of follicular carcinomas, and one case (0.9%) of medullary carcinoma were diagnosed.