M.Med. (Medical Genetics)--University of the Witwatersrand, Faculty of Health Sciences, School of Pathology, 2012 / Down syndrome (DS) (OMIM #190685), the most common viable chromosome abnormality, is associated with an increased risk of medical complications. The most frequent endocrine abnormalities observed in children with DS involve the thyroid gland, and the risk of thyroid dysfunction increases with age. Global studies have documented a wide spectrum of thyroid dysfunction in children with DS. Due to the paucity of data from sub-Saharan Africa regarding thyroid function in African children with DS, this study was conceived. The main aim of the study was to document the range of thyroid function in a cohort of 391 South African children with DS, seen at the Genetic Clinics from 2003 to 2008. Referral and treatment practices at two tertiary hospitals in Johannesburg were also documented. The majority (84%) of children had at least one thyroid function test (TFT) performed, and the most common form of thyroid dysfunction encountered was subclinical hypothyroidism (25.3%). Notably, up to one third of patients with abnormal TFT results were not referred to the Endocrine Clinics for evaluation, and were thus not receiving the necessary treatment. There were 13 neonates with congenital hypothyroidism; at least two of them were not referred, and thus not treated during the sensitive neonatal period. A significant difference was noted between the results from Chris Hani Baragwanath Hospital and those from the other two hospitals. The difficulties in interpretation of results obtained from different biochemical machines and different populations, as compared to those used to derive the reference ranges, were raised. Problems with regular follow-up of patients and annual thyroid surveillance were also highlighted. The clinical features of hypothyroidism may be difficult to distinguish from the phenotypic features of DS. Thus, regular biochemical screening, even in the absence of physical signs and symptoms, is warranted in this group of children to ensure that hypothyroidism is treated, and further, irreversible neurological and physical impairment prevented.

This document only includes an excerpt of the corresponding thesis or dissertation. To request a digital scan of the full text, please contact the Ruth Lilly Medical Library's Interlibrary Loan Department (rlmlill@iu.edu).

No description available.

Over the past several decades, the incidence of thyroid cancer in the United States has increased substantially surmounting to higher levels of concern for physicians around the nation. This concern led to a research investigation surrounding the increased risk thyroid cancer patients may face by delaying their surgeries. OBJECTIVE: We aim to evaluate the impact of a delay in surgical intervention on survival in patients with a diagnosis of papillary thyroid cancer. METHODS: This is an observational retrospective study focusing on disease specific survival using SEER-Medicare data as well as data from the National Cancer Database to analyze whether a delay in surgical intervention leads to a decrease in mortality in patients with papillary thyroid cancer. This study focuses on specific thyroid cancer association beyond that of another research paper that found delaying time to surgery does decrease overall survival as discovered by Dr. Scott Fligor in 2021. For the purposes of this study, data was accessed between the years 1999-2018. A survival analysis was performed using the Cox- hazard ratio as well as Kaplan-Meier curves. RESULTS: Preliminary results detail the fact that delaying surgeries past 180 days for patients led to decreased survival over a course of 5, 10, and 15 years as was determined by the use of Kaplan Meyer curves and the Cox hazard ratio. A positive coefficient for a Cox hazard ratio indicates a worse prognosis whereas a negative coefficient indicates the opposite. The results of this study show that increasing time to surgery increases risk of mortality for patients as the hazard ratios suggest for this research. The hazard ratio for 90 – 180 days delay for patients versus patients who underwent surgery within 0 – 90 days was 1.18 (95% confidence internal, 0.96 – 1.45). This hazard ratio is lower than that of the group that underwent surgery after 180+ days whose hazard ratio was 1.21 (95% confidence internal, 0.89 – 1.66). Since the hazard ratio for patients who delayed surgery after 180+ days is higher than the 0 – 90 days as well as the 90 – 180 days, this indicates a worse prognosis over time for patients with increased delays. CONCLUSION: Delaying surgery for thyroid cancer patients deceases their overall survival over a period of 5, 10, and 15 years. Elective or lower risk surgeries over the past 3 years have been delayed due to the Covid-19 pandemic, and thus this data was excluded for the purposes of this study. Further research should be done on the effects the pandemic had on the overall survival for patients who had to delay their surgeries due to the pandemic.

No description available.

No description available.

No description available.

No description available.

PCBs are known to cause thyroid disruption in laboratory rats and are thought to be the causal agent in thyroid gland alterations in herring gulls in the Great Lakes. This study examined the regulation of thyroid hormone supply during development in (1) domestic chicken embryos (Gallus domesticus) exposed to a specific dioxin-like PCB congener (PCB-126) and (2) herring gull (Larus argentatus) embryos and pre-fledglings from Great Lakes sites with different chemical pollutant exposures. Specifically, PCB effects on thyroid status were evaluated by measuring plasma thyroid hormone concentrations and brain type II 5'D activity (to determine if PCB exposure was associated with alteration in brain 5'D type II activity that could maintain local T3 supply to the brain). If PCB-126 and PCB mixtures altered thyroid function, we expected to see decreased plasma thyroid hormone concentrations and subsequent increases in 5'D-II activity. Chicken eggs were injected (into the air cell) before incubation with five dose levels (0.0512, 0.128, 0.32, 0.64, 0.8 ng/g) of PCB-126 (3,3, 4,4',5-pentachlorobiphenyl), or vehicle (sunflower oil); sampling was on day 20 of the 21-day incubation period. Studies on PCB-treated embryos included a preliminary study and a larger study encompassing a serious of smaller studies. Herring gull embryos (at pipping, on day 25 of the 26 day incubation), and 28-day pre-fledgling chicks were sampled (for two field seasons) at several Great Lakes sites with different contaminant exposures (with Kent Island being the reference site). In PCB-treated chicken embryos, there were no statistically significant decreases in plasma T4 or T3 concentrations and no significant increases in brain 5'D-II activity in either the preliminary or the larger study. We found no clear pattern of altered thyroid function in herring gulls from polluted Great Lakes' sites. Plasma TH concentrations were not significantly decreased and 5'D-II activity did not significantly increase in birds from more contaminated sites in comparison to birds from Kent Island or sites with less contamination. Although pipped embryos from Strachnan Island had a significant increase in 5'D-II activity when compared to Kent Island, there were no differences in plasma TH concentrations, and brain 5'D-II activity was not significantly increased in birds from sites with greater PCB loads than Strachnan Island. Plasma T4 and T3 concentrations were significantly decreased in prefledglings from West Sister Island and Detroit Edison in comparison to Kent Island, but there was no subsequent increase in brain 5'D-II activity. The present study is the first to evaluate the potential effects of PCBs, alone and in a mixed environmental exposure, on circulating THs and brain 5'D-II activity in developing birds. Although thyroid function was not altered by the specific PCB congener used in my study or by exposure to environmental pollutants, more complete evaluations are needed before determining whether PCBs alter thyroid function in birds. / Master of Science

The purpose of this study was to report the scintigraphic and sonographic appearance of the thyroid gland in clinically normal horses so these modalities could be used to assess the thyroid gland in this species. Horses were divided into two age groups. Group A consisted of 8 horses between 3 and 10 years of age and Group B of 7 horses between 11 and 20 years of age. Total T4 concentrations were within the laboratory reference interval. Thyroid to salivary (T/S) ratio, percent dose uptake of pertechnetate and thyroid lobe volume were calculated. Echogenicity of thyroid lobes and presence of nodules were documented. The two groups were compared using appropriate parametric and nonparametic tests. Total T4 concentrations were significantly lower in the older group. Sixty minute mean ± standard deviation (SD) T/S ratios for older versus younger horses were 5.8 ± 3.0 and 5.3 ± 2.2, respectively. Sixty minute median and interquartile ranges for percent dose uptake of pertechnetate for older versus younger horses were 3.64% (1.5 to 3.98%) and 2.55% (2.33 to 2.90%), respectively. Mean ± SD thyroid lobe volumes for older versus younger horses were 18.93 ± 5.16 cm3 and 13.55 ± 3.56 cm3, respectively. Most thyroid lobes were hyper or isoechoic to the sternocephalicus muscle. Prevalence of thyroid nodules did not differ between groups. Older horses had trends for greater T/S ratios, percent dose uptakes and thyroid lobe volumes but had lower total T4 concentrations. Further studies using scintigraphy and ultrasound in horses with thyroid disease are planned. / Master of Science