Conversion of autoimmune hypothyroidism to hyperthyroidism

Autoimmune Thyroid Diseases

Autoimmune thyroid diseases (AITDs) include a wide spectrum of thyroid diseases affecting more commonly women than men. The most frequent forms are Graves' Disease (GD) and Hashimoto's thyroiditis / Autoimmune Thyroiditis (AIT), but there are also other immunogenic destructive forms of thyroiditis, that is, silent and postpartum thyroiditis. In the last decade, AITDs and other inflammatory thyroid diseases related to anti-tumor molecular drugs are more frequently seen due to the widespread use of tyrosine kinase inhibitors (TKIs) and immune checkpoint inhibitors (ICPIs). Autoimmune thyroiditis related to SARS-CoV-2 infection has been a novel entity in recent years. Graves' Disease and AIT may shift from hyperthyroidism to hypothyroidism, which may complicate the differential diagnosis and further treatment strategy. Moreover, all AITDs may manifest with thyrotoxicosis (a clinical condition marked with high serum levels of thyroid hormones) which has to be distinguished from hyperthyroidism (increased thyroid hormone production and secretion as a result of hyperfunctioning thyroid gland) due to different therapeutic approaches. Nuclear medicine techniques, such as radioiodine uptake (RAIU) and thyroid scintigraphy, using 99mTc- pertechnetate (Na[99mTc]TcO4) or 123-Iodine (Na[123I]I), have a crucial role in the differential diagnosis. Measurement of thyroid antibodies, e.g. thyroid peroxidase antibodies (TPO) and thyrotropin receptor antibodies (TRAb), as well as thyroid ultrasound, are complementary methods in the evaluation of thyroid disorders.

Effects of block-replace regimen in patients with autoimmune hypothyroidism converted to Graves' disease

PURPOSE

We present two cases of autoimmune hypothyroidism converted to Graves' disease (GD) and their medical management.

METHODS

We tested thyroid function and thyroid antibodies and performed an ophthalmologic examination and neck ultrasound in two patients with autoimmune hypothyroidism converted to GD during a follow-up of several years.

CASE REPORTS

The first case is a 33 year-old woman with hypothyroidism due to Hashimoto's thyroiditis (HT). She developed signs and symptoms of hyperthyroidism after 7 years of treatment with the same dose of levothyroxine (LT4). Even when LT4 therapy was discontinued, she remained thyrotoxic, with mild Graves' ophthalmopathy (GO) and very high thyroid-stimulating hormone receptor antibodies (TRAb > 40 IU/L, reference range: <1.75 IU/L). Antithyroid medication was started on a titration regimen, without achievement of euthyroidism. She was switched to a block and replace regimen, using 20 mg of methimazole (MMI) and 75 mcg of LT4 daily, with normalization of thyroid hormones and improvement of GO without steroids. The second case is a 57 year-old man with a 2-year positive medical history of HT and 6 months of LT4 treatment. He developed hyperthyroidism and moderate-severe GO. Despite stopping LT4 and initiating antithyroid medication in a titration regimen, he did not achieve euthyroidism and had active GO. Pulse glucocorticoid therapy and switching to a block-replace regimen was required to achieve euthyroidism and reduce ocular proptosis and diplopia.

CONCLUSION

Spontaneous autoimmune conversion of hypothyroidism to hyperthyroidism can occur at any time: it is important to promptly identify these cases so as to manage them effectively.

The Thyroid Swing: A Patient's Journey From Hypothyroidism to Hyperthyroidism

The flip from hyperthyroidism (HT), as observed in Graves' disease (GD) cases, to hypothyroidism associated with Hashimoto's disease (HD) has been widely recognized and documented. However, the converse is infrequently observed. The observed phenomenon is likely attributed to the major role played by thyroid-stimulating hormone receptor antibodies (TRAbs) in this alternating disease pattern and a substantial reduction in thyroid tissue mass that could be stimulated by these antibodies. Therefore, here we present a case of one middle-aged individual experiencing this transitional switch from hypothyroidism to GD. A 42-year-old male patient diagnosed with HD-related hypothyroidism for two years has remained stable with levothyroxine medication since diagnosis. However, his symptoms of thyrotoxicosis, such as anxiety, weight loss, and palpitations, had appeared during his follow-up time at the clinic. Physical examination revealed mild exophthalmos, which confirmed HT by thyroid function test results. The possibility of levothyroxine-induced HT was initially considered, although the observed symptoms failed to ameliorate despite the reduction and discontinuation of levothyroxine. The diagnosis of GD was confirmed after subsequent examination, and a follow-up was carried out. This particular case study underscores a distinctive correlation that carries substantial implications for the diagnosis and treatment of GD. The consideration of this shift is warranted in cases where HT continues to exist despite the reduction or cessation of levothyroxine treatment. The diagnosis is established through antibody titers and a radioiodine uptake scan. Treatment choice is based on the illness's stage and the patient's and care provider's preferences. In the initial phase, anti-thyroid medications may be employed. It is imperative to conduct regular follow-ups on these patients due to the potential transient nature of this clinical condition.

Mapping the path towards novel treatment strategies: a bibliometric analysis of Hashimoto's thyroiditis research from 1990 to 2023

Background

Hashimoto's thyroiditis (HT), a common form of thyroid autoimmunity, is strongly associated with deteriorating clinical status and impaired quality of life. The escalating global prevalence, coupled with the complexity of disease mechanisms, necessitates a comprehensive, bibliometric analysis to elucidate the trajectory, hotspots, and future trends in HT research.

Objective

This study aims to illuminate the development, hotspots, and future directions in HT research through systematic analysis of publications, institutions, authors, journals, references, and keywords. Particular emphasis is placed on novel treatment strategies for HT and its complications, highlighting the potential role of genetic profiling and immunomodulatory therapies.

Methods

We retrieved 8,726 relevant documents from the Web of Science Core Collection database spanning from 1 January 1990 to 7 March 2023. Following the selection of document type, 7,624 articles were included for bibliometric analysis using CiteSpace, VOSviewer, and R software.

Results

The temporal evolution of HT research is categorized into three distinct phases: exploration (1990-1999), rapid development (1999-2000), and steady growth (2000-present). Notably, the United States, China, Italy, and Japan collectively contributed over half (54.77%) of global publications. Among the top 10 research institutions, four were from Italy (4/10), followed by China (2/10) and the United States (2/10). Recent hotspots, such as the roles of gut microbiota, genetic profiling, and nutritional factors in HT management, the diagnostic dilemmas between HT and Grave's disease, as well as the challenges in managing HT complicated by papillary thyroid carcinoma and type 1 diabetes mellitus, are discussed.

Conclusion

Although North America and Europe have a considerable academic impact, institutions from emerging countries like China are demonstrating promising potential in HT research. Future studies are anticipated to delve deeper into the differential diagnosis of HT and Grave's disease, the intricate relationship between gut microbiota and HT pathogenesis, clinical management of HT with papillary thyroid carcinoma or type 1 diabetes, and the beneficial effects of dietary modifications and micronutrients supplementation in HT. Furthermore, the advent of genetic profiling and advanced immunotherapies for managing HT offers promising avenues for future research.

Autoimmune Thyroiditis Shifting from Hashimoto's Thyroiditis to Graves' Disease

In 15-20% of cases, Graves' disease (GD) shifts to Hashimoto's thyroiditis (HT), while the shift from HT to GD is rare. We present a case of a patient in whom HT shifted to GD, along with a literature review. A 50-year-old woman with myxedema was diagnosed with Hashimoto's disease due to hypothyroidism and the presence of antibodies against thyroid peroxidase (TPOAb) and thyroglobulin (TgAb); she also had thyroid stimulating antibodies (TSAb) without any signs of GD. Although thyroid hormone replacement therapy improved her thyroid function, 2 months later, hyperthyroidism appeared and did not improve after discontinuation of the replacement therapy. The patient was diagnosed with GD, which improved with antithyroid agent administration. To date, only 50 cases regarding conversion from HT to GD have been reported. The median age is 44 years (range, 23-82 years), and the median time of conversion is 7 years (range, 0.1-27 years). The male-to-female ratio of HT conversion to GD is 1:9, closer to that of regular GD (1:10) than that of general HT (1:18). All patients received thyroid hormone replacement therapy for hypothyroidism due to HT. Continuous evaluation of TSAb levels is recommended in HT, particularly in cases of TSAb-positive and those under replacement, since it may help predict conversion to GD. Evaluating the clinical characteristics of patients with HT preceding GD is crucial to ensure appropriate treatment and reduce the risk of adverse events.

A case of hyperchylomicronemia associated with GPIHBP1 autoantibodies and fluctuating thyroid autoimmune disease

Recent studies have reported that patients with autoimmune hyperchylomicronemia caused by glycosylphosphatidylinositol-anchored high-density lipoprotein binding protein 1 (GPIHBP1) autoantibodies are associated with rheumatoid arthritis, systemic lupus erythematosus, Sjogren's syndrome, Hashimoto's thyroiditis, Basedow's disease, and immune thrombocytopenia. We report a rare case of hyperchylomicronemia due to GPIHBP1 autoantibodies and fluctuating thyroid autoimmune disease. A 28-year-old woman, diagnosed with Hashimoto's thyroiditis at 26 years of age, started taking 50 µg/day of levothyroxine sodium. She had an episode of acute pancreatitis at 27 years of age; her serum triglyceride (TG) level was 1291 mg/dL at that time. The patient was referred to our hospital because her hyperchylomicronemia (hypertriglyceridemia) did not improve on treatment with pemafibrate and eicosapentaenoic acid (EPA). Serum total cholesterol and TG levels were 237 mg/dL and 2535 mg/dL, respectively, while plasma pre-heparin lipoprotein lipase (LPL) mass was 15 ng/mL (26.5-105.5 ng/mL). We diagnosed her as Basedow's disease based on autoimmune antibodies and ultrasound examination. Targeted exome sequencing revealed no pathogenic variants in the LPL or GPIHBP1 genes. The serum GPIHBP1 autoantibody level was 686.0 U/mL (<58.4 U/mL) and GPIHBP1 mass was 301.9 pg/mL (570.6-1625.6 pg/mL). The patient showed hyperchylomicronemia during periods of hypothyroidism and hyperthyroidism, whereas GPIHBP1 autoantibodies were positive during episode of hyperchylomicronemia but negative during periods of normal TG levels. Based on these findings, the patient was diagnosed with hyperchylomicronemia due to GPIHBP1 autoantibodies and treated with rituximab. GPIHBP1 autoantibodies remained undetectable and TG levels were controlled at approximately 200 mg/dL.

Spectrum of thyroid disease in a single patient: A case of papillary thyroid carcinoma in a patient with Graves' disease and Hashimoto's thyroiditis

A 65‐year‐old man with a history of Hashimoto's thyroiditi on Levothyroxine developed Graves' disease with ocular symptoms and was treated with teprotumumab without improvement. Total thyroidectomy was performed to control hyperthyroidism. Surgical pathology revealed multifocal papillary thyroid carcinoma. Rarely, a spectrum of thyroid disorders is seen in a single patient.

Fluctuating Hyperthyroidism and Hypothyroidism in Graves’ Disease: The Swinging Between Two Clinical Entities

Autoimmune thyroid disorders are frequently encountered in clinical practice and consist of a spectrum ranging from Graves’ hyperthyroidism to Hashimoto's hypothyroidism. Generally, patients with autoimmune thyroid disorders will lean towards one end of the spectrum or the other, with fluctuations between hyper- and hypothyroidism rarely seen. This is especially the case when persistent hyperthyroidism occurs after a prolonged period of hypothyroidism. Here, we present a case of a young female patient initially presenting with Graves’ disease with a previous history of hypothyroidism.

Graves' disease: A rare fate of Hashimoto's thyroiditis

Hashimoto's thyroiditis is a known autoimmune disorder that leads to chronic inflammation of the thyroid gland, with a gradual decline in function and eventual hypothyroidism. Conversion of Hashimoto's thyroiditis to Graves' disease is unusual clinically and has been occasionally reported in the literature. Awareness of such a rare phenomenon is important for the physicians evaluating patients with autoimmune thyroid disorders. Close investigation of the patient's symptoms and biochemical status is crucial in the implementation of appropriate treatment.

The Unusual Late-Onset Graves' Disease following Hashimoto's Related Hypothyroidism: A Case Report and Literature Review

Background. The shift of Graves' disease (GD) to Hashimoto's disease- (HD-) related hypothyroidism is well established. However, the opposite is rare. This is likely to the loss of critical thyroid mass available for stimulation by thyroid hormone receptor stimulating antibody, making this shift unusual. Herein, we report a young lady with a late shift from HD into GD and present a scoping literature review. Case presentation. We report a twenty-five-year-old lady with a sixteen-year-history of Hashimoto's-related hypothyroidism stable on levothyroxine. While following in the clinic, she started developing thyrotoxic symptoms in the form of anxiety, weight loss, and palpitation. Physical examination was remarkable for mild exophthalmos. The thyroid function test confirmed hyperthyroidism. Levothyroxine-induced hyperthyroidism was initially suspected; however, the symptoms did not improve despite reducing and stopping levothyroxine. Subsequent workup confirmed the diagnosis of GD. Discussion and Conclusion. This case highlights a unique association that has significant diagnostic and management implications. This shift should be considered when hyperthyroidism persists despite reducing or stopping levothyroxine. The diagnosis is made utilizing antibody titers and radioiodine update scan. While the management depends on the disease's stage and the treating physician preference, antithyroid agents can be used initially. Following up these patients is essential as the shift can be transient.

[The development of Graves' disease after long-term hypothyroidism due to Hashimoto's disease]

The main autoimmune thyroid diseases are Hashimoto's thyroiditis (HT) and Graves' disease (GD). Despite the significant differences in a pathogenesis and a clinical picture between HT and GD, the literature describes the cases of the conversion of one autoimmune disease to another, which, according to one version, is associated with a change in the balance between the levels of a stimulating and blocking antibodies to the thyroid-stimulating hormone receptor. At the same time, there are more frequent observations of the transition of GD to HT, and much less often describe, on the contrary, the development of GD against the background of HT. The article presents a clinical case of the conversion of HT to GD. A detailed algorithm of the conservative management according to the «block-replace» scheme is described, indicating the results of laboratory and instrumental examination. At the time of describing the clinical case, the result of the treatment can be considered successful. The predictors such as a low level of the thyroid-stimulating hormone receptor and thyroid volume before discontinuation of the thyrostatic therapy suggest a low risk of the recrudescence of GD.According to the authors, the phenomenon of the conversion of one autoimmune thyroid disease to another, in addition to the scientific interest, is important for the practitioners, since a timely change in the diagnostic paradigm can significantly change the treatment strategy and the favorably affect the prognosis of disease, preventing the development of complications.

Basedow's disease with associated features of Hashimoto's thyroiditis based on histopathological findings

BACKGROUND

Basedow's disease and Hashimoto's thyroiditis are autoimmune thyroid disorders and usually diagnosed with elevation of serum autoimmune antibodies. Thyrotropin receptor antibodies (TRAb) and/or thyroid-stimulating antibody (TSAb) are usually used for diagnosis of Basedow's disease, and thyroid peroxidase antibodies (TPOAb) and/or thyroglobulin antibodies (TgAb) are for diagnosis of Hashimoto's thyroiditis. However, it is difficult to diagnose a subject as Basedow's disease with associated features of Hashimoto's thyroiditis only with elevation of such autoimmune antibodies.

CASE PRESENTATION

A 44-year-old woman with 5-year history of Basedow's disease underwent a total thyroidectomy. She did not have a goiter. TRAb, TSAb, TPOAg and TgAb were all positive before a total thyroidectomy. In histopathological macroscopic examination, diffuse hyperplasia of the thyroid gland was observed. Furthermore, in histopathological microscopic examination, both characteristics of Basedow's disease and Hashimoto's thyroiditis were observed. After a total thyroidectomy, titers of all thyroid-associated autoimmune antibodies were markedly reduced.

CONCLUSION

Herein, we report a subject with Basedow's disease without a goiter whose TPOAb and TgAb were relatively high at the onset of Basedow's disease. In addition, interestingly, the histopathological findings of this subject showed direct signs of Basedow's disease and Hashimoto's thyroiditis in the same thyroid gland. Considering from such findings, she seemed to have Basedow's disease with associated features of Hashimoto's thyroiditis. In conclusion, we should bear in mind the possibility of Basedow's disease with associated features of Hashimoto's thyroiditis in subjects with Basedow's disease, particularly when TPOAb and TgAb as well as TRAb and TSAb are positive.

The clinical phenotype of Graves' disease occurring as an isolated condition or in association with other autoimmune diseases

PURPOSE

Graves' disease (GD) can present as an isolated disease (iGD) or in association with other autoimmune diseases (aGD). The aim of this study, performed in two Endocrine referral centers settled in different geographical areas of Italy, was to compare the anthropometric, clinical, and biochemical phenotype of iGD patients with that of the aGD ones.

METHODS

Clinical history, physical examination data, serum levels of TSH, FT4, FT3, thyroglobulin (TgAb), thyroid-peroxidase (TPOAb) and TSH-receptor (TRAb) antibody, presence of Graves' orbitopathy (GO), and thyroid ultrasound examination at disease diagnosis were recorded.

RESULTS

68 aGD and 136 iGD patients were consecutively recruited. At diagnosis, aGD and iGD patients did not differ for F/M ratio, age at presentation, thyroid function parameters, serum levels of TRAb, TgAb, TPOAb, presence of GO, and thyroid volume. The serum levels of TRAb were strongly correlated with the circulating concentrations of both FT3 (ρ = 0.667; p < 0.0001) and FT4 (ρ = 0.628; p < 0.001) in iGD patient, but not in the aGD ones (FT3: ρ = 0.231; p = 0.058; FT4: ρ = 0.096; p = 0.435). Compared with iGD patients, the aGD ones displayed a higher rate of transition from the previous hypothyroidism to hyperthyroidism (χ² = 6.375; p = 0.012).

CONCLUSION

Despite similar anthropometric, clinical, and biochemical features at diagnosis, aGD patients display a higher rate of transition from a thyroid functional status to the other as compared with iGD patients.

Association and gene-gene interaction analyses for polymorphic variants in CTLA-4 and FOXP3 genes: role in susceptibility to autoimmune thyroid disease

PURPOSE

Polymorphic variants of cytotoxic T-lymphocyte antigen-4 (CTLA-4) and forkhead box protein P3 (FOXP3) genes are implicated in dysregulated immune homeostasis and autoimmune disorders. We analyzed the association between CTLA-4 rs231775 and FOXP3 rs3761548, rs3761549 polymorphisms and predisposition to autoimmune thyroid disease (AITD), inclusive of Hashimoto's thyroiditis (HT) and Graves' disease (GD) in South-Indian population.

METHODS

A total of 355 AITD subjects (comprising 275 HT and 80 GD) and 285 randomly selected age- and sex-matched control subjects were genotyped for the aforementioned polymorphisms by PCR-RFLP method.

RESULTS

The rs231775 "G" allele was preponderant in HT and GD subjects when compared with controls and exerted a dominant influence on the susceptibility to HT (p = 0.009) and GD (p = 0.02), respectively. There was no allelic association of rs3761548 and rs3761549 polymorphisms with AITD susceptibility, albeit a significant difference in genotype distribution with respect to rs3761549. Haplotype analysis revealed an increased frequency of rs3761548 "C"-rs3761549 "T" in HT and GD subjects, thereby associating it with disease predisposition (p = 0.03). Epistatic interaction analysis by multifactor dimensionality reduction approach revealed redundancy between CTLA-4 and FOXP3 genes in influencing the susceptibility to AITD.

CONCLUSIONS

The genetic variation in CTLA-4 gene with reference to rs231775 polymorphism contributes to an increased predisposition to HT and GD. Also, in conjunction with FOXP3 gene variants it seems to influence the susceptibility to HT and GD respectively. The significance of these findings in combination with antithyroid antibody screening could plausibly contribute towards meticulous case-finding for effective treatment of HT and GD.

Graves' disease following hypothyroidism due to Hashimoto's thyroiditis in a black South African lady: a case report

Graves' disease and Hashimoto's thyroiditis are autoimmune thyroid disorders with distinct pathological and histopathological features. The conversion from Hashimoto's thyroiditis to Graves' disease has been rarely reported throughout the world with no reports in the African race to our knowledge. We here report an African lady who was initially diagnosed with primary hypothyroidism following Hashimoto's disease but later became thyrotoxic due to Graves' disease.

Conversion to Graves disease from Hashimoto thyroiditis: a study of 24 patients

OBJECTIVE

The conversion of Hashimoto's thyroiditis (HT) to hyperthyroidism due to thyrotropin receptor antibodies is intriguing and considered rare. The contribution of TSH receptor blocking antibodies (TRAb), which may be stimulators (TSAb) or blockers (TBAb), is suspected. We describe clinical and biological variables in a series of patients switching from Hashimoto's thyroiditis to Grave's disease.

SUBJECTS AND METHODS

Retrospective case study of 24 patients with Hashimoto's thyroiditis followed during 48 ± 36 months that developed later Graves' disease (GD). These variables were analysed in the hypo and hyperthyroid phase: age, sex, initial TSH, free triiodothyronine (fT3), free thyroxine (fT4), anti-TPO, TBII antibodies, parietal cell autoantibodies, time between hypo and hyperthyroidism, thyroid volume and levothyroxine doses (LT).

RESULTS

In HT, mean TSH was 9.4 ± 26.1 UI/L and levothyroxine treatment was 66.2 ± 30.8 µg/day. The switch to GD was observed 38 ± 45 months after HT diagnosis. As expected, we found significant differences on TSH, FT3, FT4 and TBAb levels. Three out of 14 patients had parietal cell autoantibodies. In two of these three cases there was an Helicobacter pylori infection. There were no significant differences between HT and GD groups with respect to thyroid volume.

CONCLUSIONS

To our knowledge, large series documenting the conversion of HT to GD are scarce. Although rare, this phenomenon should not be misdiagnosed. Suspicion should be raised whenever thyroxine posology must be tapered down during the follow-up of HT patients. Further immunological and genetic studies are needed to explain this unusual autoimmune change.

Establishment of clinical diagnosis model of Graves' disease and Hashimoto's thyroiditis

Background

A clinical diagnosis model include thyroid functions, thyroid antibodies and radioactive iodine uptake (RAIU) of patients with hyperthyroidism were established and as new evaluation indicators for the differentiation of the Graves’ disease (GD) and Hashimoto’s thyroiditis (HT).

Methods

Clinical data of patients with newly diagnosed hyperthyroidism including gender, age, thyroid function, thyroid antibodies (FT3, FT4, TSH, TPOAb, TGAb, TRAb), RAIU (2 h, 6 h, 24 h) were collected. A stepwise regression analysis was performed to establish a model based on these variables.

Results

Model 1 was subjected to stepwise regression analysis. After screening, the variables that entered the model included FT3, TGAb, TPOAb, TRAb, 2-h RAIU, 24-h RAIU and gender, in which the variables FT3, TGAb, TRAb, 2-h RAIU, 24-h RAIU, and gender were significantly different. Model 2 without RAIU was also subjected to stepwise regression analysis. After screening, the variables that entered the model included FT4, TGAb, TPOAb, TRAb and gender were statistical significant. The larger value of each variable in the two models indicated the higher probability to diagnose GD. The area under the receiver operating characteristic (ROC) curve of model 1 was 0.843 (95% CI 0.779–0.894), and the area under the ROC curve of model 2 was 0.806 (95% CI 0.685–0.824), which showed good differential diagnostic value.

Conclusions

GD and HT diagnosis model was established according to the variables including gender, FT3, TGAb, TRAb, the 2-h RAIU, the 24-h RAIU in the model 1, and the variables FT4, TGAb, TPOAb, TRAb and gender in the model 2 that did not include RAIU. These models had high value to differentiate GD and HT for patients with early hyperthyroidism.

Phenomic Impact of Genetically-Determined Euthyroid Function and Molecular Differences between Thyroid Disorders

BACKGROUND

The thyroid plays a key role in development and homeostasis, but it has been difficult to establish causality with diseases and phenotypic traits because of several potential confounders.

METHODS

To determine the causal effect of euthyroid function, we conducted a two-sample Mendelian randomization study of euthyroid thyrotropin (TSH) and free thyroxine (FT4) levels with respect to 2419 traits assessed in 337,199 individuals from UK Biobank. Additionally, we investigated the molecular differences between hypothyroidism and hyperthyroidism using genome-wide data.

RESULTS

After multiple testing correction, sixteen traits appear to be affected by genetically-determined euthyroid TSH, including multiple thyroid-related traits, e.g., hypothyroidism (p = 2.39 × 10-17), height (p = 2.76 × 10-10), body fat distribution (impedance of whole body, p = 4.43 × 10-8), pulse rate (p = 2.84 × 10-8), female infertility (p = 4.91 × 10-6), and hearing aid use (p = 7.10 × 10-5). Moreover, we found a consistent genetic correlation between hypothyroidism and hyperthyroidism (rg = 0.45, p = 5.45 × 10-6) with several immune pathways shared between these diseases. Two molecular pathways survived multiple testing correction for specificity to hyperthyroidism, JAK/STAT signaling (p = 1.02 × 10-6) and Rac guanyl-nucleotide exchange factor activity (p = 4.39 × 10-6).

CONCLUSION

Our data shed new light on the inter-individual variability of euthyroid function and the molecular mechanisms of the two thyroid disorders investigated.

Alternating hyperthyroidism and hypothyroidism in Graves' disease

Spontaneously oscillating thyroid function in Graves' disease is a rare phenomenon. Switching between TSH receptor stimulating antibodies (TSAb) and TSH receptor blocking antibodies (TBAb) most likely accounts for presentations of alternating hyperthyroidism and hypothyroidism. To achieve stability of thyroid function, definitive therapy is recommended to remove the pathological thyroid.

Pesticide Use and Incident Hypothyroidism in Pesticide Applicators in the Agricultural Health Study

BACKGROUND

Though evidence suggests that some pesticides may have thyroid-disrupting properties, prospective studies of associations between specific pesticides and incident thyroid disease are limited.

OBJECTIVE

We evaluated associations between use of specific pesticides and incident hypothyroidism in private pesticide applicators in the Agricultural Health Study (AHS).

METHODS

Self-reported incident hypothyroidism ([Formula: see text] cases) was studied in relation to ever-use and intensity-weighted cumulative days of pesticide use at study enrollment. We estimated adjusted hazard ratios (HRs) and 95% confidence intervals (CI) using Cox proportional hazards models applied to 35,150 male and female applicators followed over 20 y. All models were stratified by state and education to meet proportional hazards assumptions ([Formula: see text] for age x covariate interactions). Models of pesticides that did not meet proportional hazards assumptions were stratified by median attained age (62 y).

RESULTS

Hypothyroidism risk was significantly increased with ever- vs. never-use of four organochlorine insecticides (aldrin, heptachlor, and lindane among participants with attained age [Formula: see text]; chlordane in all participants), four organophosphate insecticides (coumaphos in those [Formula: see text]; diazinon, dichlorvos, and malathion in all participants) and three herbicides (dicamba, glyphosate, and 2,4-D in all participants). HRs ranged from 1.21; 95% CI: 1.04, 1.41 (chlordane) to 1.54; 95% CI: 1.23, 19.4 (lindane in those [Formula: see text]). Hypothyroidism risk was greatest among those with higher intensity-weighted lifetime days of using chlordane, lindane, coumaphos (over age 62), diazinon, permethrin, and 2,4-D.

CONCLUSIONS

Our findings support associations between exposure to several pesticides and increased hypothyroidism risk. These findings are generally consistent with prior analyses of prevalent hypothyroidism in the AHS. https://doi.org/10.1289/EHP3194.

Hypothyroidism conversion to hyperthyroidism: it's never too late

Primary hypothyroidism is a common endocrine condition, most commonly caused by autoimmune thyroiditis (Hashimoto’s disease) while Graves’ disease is the most common cause of hyperthyroidism. Hypothyroidism is usually a permanent condition in most patients requiring lifelong levothyroxine treatment. Transformation from Hashimoto’s disease to Graves’ disease is considered rare but recently been increasingly recognised. We describe a case of a 61-year-old lady who was diagnosed with hypothyroidism approximately three decades ago and treated with levothyroxine replacement therapy. Approximately 27 years after the initial diagnosis of hypothyroidism, she started to become biochemically and clinically hyperthyroid. This was initially managed with gradual reduction in the dose of levothyroxine, followed by complete cessation of the medication, but she remained hyperthyroid, ultimately requiring anti-thyroid treatment with Carbimazole. This case highlights that there should be a high index of suspicion for a possible conversion of hypothyroidism to hyperthyroidism, even many years after the initial diagnosis of hypothyroidism. To our knowledge, this case illustrates the longest reported time interval between the diagnosis of hypothyroidism until the conversion to hyperthyroidism.

Pendulum swings from hypo- to hyperthyroidism: thyrotoxicosis after severe hypothyroidism following neck irradiation in a patient with a history of Hodgkin's lymphoma

Background

A change in a thyrometabolic state from severe hypothyroidism to thyrotoxicosis is very uncommon, but possible in some circumstances.

Case presentation

A 27-year old female presented with clinical and biochemical thyrotoxicosis with a previous history chemo- and radiotherapy (including the neck region) for a Hodgkin’s lymphoma (at the age of 18). At the age of 20 this was followed by severe hypothyrodism [TSH > 100 μIU/mL (reference range: 0.27–4.2)]. She was stated on L-thyroxine, but the dose was later reduced and subsequently discontinued. She had significantly elevated titres of both anti-thyroid peroxidase antibodies and anti-TSH-receptor antibodies throughout the course of disease. Thyroid scintigraphy revealed a normal and homogenous iodine uptake.

Conclusions

We suspect that a gradual switch from thyroid-blocking to thyroid-stimulating antibodies resulted in development of an overt thyrotoxicosis, possibly with a contributory effect of neck irradiation on her autoimmune status.