Thyroid Hormone Metabolism Research Articles

Exposure to MEHP during Pregnancy and Lactation Impairs Offspring Growth and Development by Disrupting Thyroid Hormone Homeostasis.

Mono(2-ethylhexyl) phthalate (MEHP), as a highly toxic and biologically active phthalate metabolite, poses considerable risks to the environment and humans. Despite the existence of in vitro studies, there is a lack of in vivo experiments assessing its toxicity, particularly thyroid toxicity. Herein, we investigated the thyroid-disrupting effects of MEHP and the effects on growth and development of maternal exposure to MEHP during pregnancy and lactation on the offspring modeled by SD rats. We found that thyroid hormone (TH) homeostasis was disrupted in the offspring, showing a decrease in total TH levels, combined with an increase in free TH levels. Nonhomeostasis ultimately leads to weight loss in female offspring, longer anogenital distance in male offspring, prolonged eye-opening times, and fewer offspring. Our findings indicate that maternal exposure to MEHP during pregnancy and lactation indirectly influences the synthesis, transport, transformation, and metabolism of THs in the offspring. Meanwhile, MEHP disrupted the morphology and ultrastructure of the thyroid gland, leading to TH disruption. This hormonal disruption might ultimately affect the growth and development of the offspring. This study provides a novel perspective on the thyroid toxicity mechanisms of phthalate metabolites, emphasizing the health risks to newborns indirectly exposed to phthalates and their metabolites.

Growth hormone-secreting pituitary adenoma combined with Graves' disease: retrospective case series and literature review.

The coexistence of growth hormone-secreting pituitary adenoma (GHPA) and Graves' disease (GD) is rare. This study aimed to investigate the relationship between growth hormone (GH)/insulin-like growth factor 1 (IGF-1) levels and thyroid function in patients with GHPA combined with GD and to explore the underlying mechanisms. Eleven patients with GHPA combined with GD during 2015-2022 were collected by searching the medical record system of Beijing Tiantan Hospital, Capital Medical University. Changes in GH/IGF-1 levels and thyroid function were compared before and after the application of antithyroid drugs (ATD) and before and after transsphenoidal surgery (TSS) or somatostatin analog (SSA) treatment, respectively. After the application of ATD, with the decrease of thyroid hormone levels, GH/IGF-1 levels also decreased gradually. In patients without ATD application, after surgery or SSA treatment, thyroid hormone levels decreased as GH/IGF-1 decreased. Hyperthyroidism due to GD promotes the secretion of GH/IGF-1, and when thyroid hormone levels were decreased by the use of ATD, GH and IGF-1 levels were also decreased, suggesting that thyroid hormones may influence the synthesis and secretion of GH/IGF-1. The use of ATD to control thyrotoxicosis before TSS is not only beneficial in reducing the risk of anesthesia but may help to promote biochemical control of GHPA. On the other hand, high levels of GH/IGF-1 in patients with GHPA also exacerbate GD hyperthyroidism, which is ameliorated by a decrease in GH/IGF-1 levels by TSS or SSA treatment, suggesting that the GH-IGF-1 axis promotes growth, thyroid function, and thyroid hormone metabolism.

The ecological function of thyroid hormones.

Thyroid hormones (TH) are central hormonal regulators, orchestrating gene expression and complex biological processes vital for growth and reproduction in variable environments by triggering specific developmental processes in response to external cues. TH serve distinct roles in different species: inducing metamorphosis in amphibians or teleost fishes, governing metabolic processes in mammals, and acting as effectors of seasonality. These multifaceted roles raise questions about the underlying mechanisms of TH action. Recent evidence suggests a shared ecological role of TH across vertebrates, potentially extending to a significant portion of bilaterian species. According to this model, TH ensure that ontogenetic transitions align with environmental conditions, particularly in terms of energy expenditure, helping animals to match their ontogenetic transition with available resources. This alignment spans post-embryonic developmental transitions common to all vertebrates and more subtle adjustments during seasonal changes. The underlying logic of TH function is to synchronize transitions with the environment. This review briefly outlines the fundamental mechanisms of thyroid signalling and shows various ways in which animals use this hormonal system in natural environments. Lastly, we propose a model linking TH signalling, environmental conditions, ontogenetic trajectory and metabolism. This article is part of the theme issue 'Endocrine responses to environmental variation: conceptual approaches and recent developments'.

Multi-trait analysis characterizes the genetics of thyroid function and identifies causal associations with clinical implications

To date only a fraction of the genetic footprint of thyroid function has been clarified. We report a genome-wide association study meta-analysis of thyroid function in up to 271,040 individuals of European ancestry, including reference range thyrotropin (TSH), free thyroxine (FT4), free and total triiodothyronine (T3), proxies for metabolism (T3/FT4 ratio) as well as dichotomized high and low TSH levels. We revealed 259 independent significant associations for TSH (61% novel), 85 for FT4 (67% novel), and 62 novel signals for the T3 related traits. The loci explained 14.1%, 6.0%, 9.5% and 1.1% of the total variation in TSH, FT4, total T3 and free T3 concentrations, respectively. Genetic correlations indicate that TSH associated loci reflect the thyroid function determined by free T3, whereas the FT4 associations represent the thyroid hormone metabolism. Polygenic risk score and Mendelian randomization analyses showed the effects of genetically determined variation in thyroid function on various clinical outcomes, including cardiovascular risk factors and diseases, autoimmune diseases, and cancer. In conclusion, our results improve the understanding of thyroid hormone physiology and highlight the pleiotropic effects of thyroid function on various diseases.

Maternal seafood consumption is associated with improved selenium status: Implications for child health

Selenium (Se) is required for synthesis of selenocysteine (Sec), an amino acid expressed in the active sites of Se-dependent enzymes (selenoenzymes), including forms with essential functions in fetal development, brain activities, thyroid hormone metabolism, calcium regulation, and to prevent or reverse oxidative damage. Homeostatic mechanisms normally ensure the brain is preferentially supplied with Se to maintain selenoenzymes, but high methylmercury (CH3Hg) exposures irreversibly inhibit their activities and impair Sec synthesis. Due to Hg’s high affinity for sulfur, CH3Hg initially binds with the cysteine (Cys) moieties of thiomolecules which are selenoenzyme substrates. These CH3Hg-Cys adducts enter selenoenzyme active sites and transfer CH3Hg to Sec, thus irreversibly inhibiting their activities. High CH3Hg exposures are uniquely able to induce a conditioned Se-deficiency that impairs synthesis of brain selenoenzymes. Since the fetal brain lacks Se reserves, it is far more vulnerable to CH3Hg exposures than adult brains. This prompted concerns that maternal exposures to CH3Hg present in seafood might impair child neurodevelopment. However, typical varieties of ocean fish contain far more Se than CH3Hg. Therefore, eating them should augment Se-status and thus prevent Hg-dependent loss of fetal selenoenzyme activities. To assess this hypothesis, umbilical cord blood and placental tissue samples were collected following delivery of a cohort of 100 babies born on Oahu, Hawaii. Dietary food frequency surveys of the mother’s last month of pregnancy identified groups with no (0 g/wk), low (0–12 g/wk), or high (12 + g/wk) levels of ocean fish consumption. Maternal seafood consumption increased Hg contents in fetal tissues and resulted in ∼34% of cord blood samples exceeding the EPA Hg reference level of 5.8 ppb (0.029 µM). However, Se concentrations in these tissues were orders of magnitude higher and ocean fish consumption caused cord blood Se to increase ∼9.4 times faster than Hg. Therefore, this study supports the hypothesis that maternal consumption of typical varieties of ocean fish provides substantial amounts of Se that protect against Hg-dependent losses in Se bioavailability. Recognizing the pivotal nature of the Hg:Se relationship provides a consilient perspective of seafood benefits vs. risks and clarifies the reasons for the contrasting findings of certain early studies.

Antipyretic effect of inhaled Tetrastigma hemsleyanum polysaccharide on substance and energy metabolism in yeast-induced pyrexia mice via TLR4/NF-κb signaling pathway

Ethnopharmacological relevanceTetrastigma hemsleyanum Diels et Gilg, is one of the perennial evergreen plants with grass vine, which has obvious curative effect on severe infectious diseases. Although Tetrastigma hemleyanum has long been recognized for its capacity of antipyretic and antitoxic, its specific mechanism is unknown. Aim of the studyTo evaluate the antipyretic effect of Tetrastigma hemleyanum polysaccharide (THP) on mice with dry yeast-induced fever, and to explore its specific antipyretic mechanism. MethodsIn this study, THP was administered by aerosol in febrile mice. The rectal temperatures of treated animals were monitored at different time points. Histopathological evaluation and various inflammatory indexes were used to assess inflammatory damage. The concentration variations of the central neurotransmitter, endocrine system, substance and energy metabolism indicators were measured to explore the physiological mechanism. Quantitative real-time PCR, Western bolt and Immunohistochemistry were performed to identify the correlation between antipyretic and TLR4/NF-κB signaling pathway. ResultsTHP reduced the body temperature of febrile mice induced by dry yeast, as well as the levels of thermogenic cytokines and downregulated the contents of thermoregulatory mediators. THP alleviated the pathological damage of liver and hypothalamus caused by fever. In addition, THP decreased the secretion of thyroid hormone, substance and energy metabolism related indicators. Furthermore, THP significantly suppressed TLR4/NF-κB signaling pathway-related indicators. Conclusions: In conclusion, our results suggest that inhaled THP exerts antipyretic effect by mediating the thermoregulatory mediator, decreasing the content of pyrogenic factors to lower the body temperature, and eventually restoring the high metabolic level in the body to normal via inhibiting TLR4/NF-κB signaling pathway. The study provides a reasonable pharmacodynamic basis for the treatment of polysaccharide in febrile-related diseases.

Gut Microbiota Changes and Its Potential Relations with Thyroid Disorders: From Composition to Therapeutic Targets.

Composed of over 1200 species of anaerobes and aerobes bacteria along with bacteriophages, viruses, and fungal species, the human gut microbiota (GM) is vital to health, including digestive equilibrium, immunologic, hormonal, and metabolic homeostasis. Micronutrients, usually refer to trace elements (copper, iodine, iron, selenium, zinc) and vitamins (A, C, D, E), interact with the GM to influence host immune metabolism. So far, microbiome studies have revealed an association between disturbances in the microbiota and various pathological disorders, such as anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis, anxiety, depression, early-onset cancers, type 1 diabetes (T1D) and type 2 diabetes (T2D). As common conditions, thyroid diseases, encompassing Graves' disease (GD), Graves' orbitopathy (GO), Hashimoto's thyroiditis (HT), benign nodules, and papillary thyroid cancer (TC), have negative impacts on the health of all populations. Following recent studies, GM might play an integral role in triggering diseases of the thyroid gland. Not only do environmental triggers and genetic predisposing background lead to auto-aggressive damage, involving cellular and humoral networks of the immune system, but the intestinal microbiota interacts with distant organs by signals that may be part of the bacteria themselves or their metabolites. The review aims to describe the current knowledge about the GM in the metabolism of thyroid hormones and the pathogenesis of thyroid diseases and its involvement in the appearance of benign nodules and papillary TC. We further focused on the reciprocal interaction between GM composition and the most used treatment drugs for thyroid disorders. However, the exact etiology has not yet been known. To elucidate more precisely the mechanism for GM involvement in the development of thyroid diseases, future work is needed.

Thyroid hormone metabolism in renal disease

Thyroid hormone metabolism in renal disease

Causes of difficulties with adequate levothyroxine substitution - an immunoendocrine perspective.

Hypothyroidism is one of the most common endocrinopathies worldwide, the treatment of which is based on replacement therapy with levothyroxine. However, this seemingly simple treatment method is fraught with many difficulties and frequent dissatisfaction among patients. In fact, differences in response to levothyroxine probably depend on a complex interaction between individual, environmental, genetic, and epigenetic factors that are still not sufficiently understood. Immunological disturbances, underlying Hashimoto's disease, the most common cause of hypothyroidism, probably play a significant role in these relationships. Indeed, a growing number of studies indicate that autoimmunity through activation of low-grade inflammation can lead to impaired absorption, transport, metabolism, and action of thyroid hormones. This review provides an up-to-date overview of the causes responsible for both the difficulty in achieving target thyrotropin levels and persistence of nonspecific symptoms despite adequate hormone replacement from an immunoendocrine perspective. Understanding these mechanisms points to a new direction in the approach to hypothyroidism, indicating the need for new personalized treatment strategies.

Assessment of thyroid function in children and adolescents with chronic liver diseases

Introduction The majority of hepatic patients are clinically euthyroid. However, liver disorders may alter thyroid hormone metabolism, including substantial abnormalities of either euthyroid sick syndrome (ESS), autoimmune thyroid disorders, or subclinical hypothyroidism (SH). But there are few studies conducted on children with chronic liver diseases (CLD) to assess thyroid functions. Aim The study aimed to evaluate thyroid profiles in patients with CLD. Patients and methods An observational, cross-sectional study including patients with CLD attending Hepatology Clinic at Alexandria University Children’s Hospital from June 2021 to June 2022. One hundred and two children were included and a history taking and clinical examination were performed. Assessment of severity using a modified Child–Pugh score was done. Laboratory investigations in the form of liver, lipid, and thyroid profiles were done. Results One hundred and two children with CLD were included in this study, 50 (49.0%) females and 52 (51.0%) males. The most common diagnosis in the studied cases was autoimmune hepatitis (24.5%), followed by glycogen storage disease. Out of 14 (13.7%) aberrant outcomes of thyroid function, seven (6.9%) patients had ESS, and seven (6.9%) individuals had SH. By univariate analysis, alkaline phosphatase and serum albumin level were significant risk factors for SH. Furthermore, melena and hepatic encephalopathy were significant risk factors for ESS. Conclusion Thyroid dysfunction might occur in CLDs either in the form of SH or ESS. The prevalence of thyroid disease in children with CLD exceeded 10%, which signifies the importance of screening for thyroid dysfunctions in this cohort.

Bioaccumulation and thyroid endcrione disruption of 2-ethylhexyl diphenyl phosphate at environmental concentration in zebrafish larvae

2-ethylhexyl diphenyl phosphate (EHDPP) strongly binds to transthyretin (TTR) and affects the expression of genes involved in the thyroid hormone (TH) pathway in vitro. However, it is still unknown whether EHDPP induces endocrine disruption of THs in vivo. In this study, zebrafish (Danio rerio) embryos (< 2 h post-fertilization (hpf)) were exposed to environmentally relevant concentrations of EHDPP (0, 0.1, 1, 10, and 100 μg·L−1) for 120 h. EHDPP was detected in 120 hpf larvae at concentrations of 0.06, 0.15, 3.71, and 59.77 μg·g−1 dry weight in the 0.1, 1, 10, and 100 μg·L−1 exposure groups, respectively. Zebrafish development and growth were inhibited by EHDPP, as indicated by the increased malformation rate, decreased survival rate, and shortened body length. Exposure to lower concentrations of EHDPP (0.1 and 1 μg·L−1) significantly decreased the whole-body thyroxine (T4) and triiodothyronine (T3) levels and altered the expressions of genes and proteins involved in the hypothalamic-pituitary-thyroid axis. Downregulation of genes related to TH synthesis (nis and tg) and TH metabolism (dio1 and dio2) may be partially responsible for the decreased T4 and T3 levels, respectively. EHDPP exposure also significantly increased the transcription of genes involved in thyroid development (nkx2.1 and pax8), which may stimulate the growth of thyroid primordium to compensate for hypothyroidism. Moreover, EHDPP exposure significantly decreased the gene and protein expression of the transport protein transthyretin (TTR) in a concentration-dependent manner, suggesting a significant inhibitory effect of EHDPP on TTR. Molecular docking results showed that EHDPP and T4 partly share the same mode of action of binding to the TTR protein, which might result in decreased T4 transport due to the binding of EHDPP to the TTR protein. Taken together, our findings indicate that EHDPP can cause TH disruption in zebrafish and help elucidate the mechanisms underlying EHDPP toxicity.

In vitro mitochondrial and myogenic gene expression is influenced by formoterol in human myotubes

BackgroundExercise is an effective treatment for establishing and maintaining skeletal muscle health. The interconnected cascade of gene expression pathways related to myogenesis, mitochondrial homeostasis, and thyroid hormone metabolism are critical to skeletal muscle health. This in vitro study was conducted to investigate the effects of exercise mimetic (formoterol) stimulation on human skeletal muscle cell signaling during myogenesis, and to provide insight on potential targets for future studies exploring therapies for skeletal muscle atrophy. Human myoblasts were cultured and differentiated to evaluate the effects of exercise mimetic stimulation on gene expression during mid and late myogenesis.ResultsWe characterized the expression of 24 genes related to myogenesis, mitochondrial biogenesis, thyroid hormone metabolism, and cellular homeostasis and found that 21 genes were altered in response to formoterol, thus affecting related skeletal muscle pathways. Additionally, formoterol stimulation resulted in a myogenic program that appears to favor prolonged myoblast proliferation and delayed myotube maturation. Robust, yet distinctive effects of exercise mimetic stimulation on gene expression during mid-myogenesis and at terminal differentiation occurred. For instance, MYF5 increased in D6 FORM compared to other groups (p < 0.001) while MYOD and MYOG both decreased expression in the FORM groups compared to CON (p < 0.01). Secondly, mitochondrial biogenesis genes were stimulated following formoterol administration, namely PGC-1α, PGC-1β, and TFAM (p < 0.05). Uniquely in our study, thyroid hormone metabolism related genes were differentially expressed. For instance, DIO2 and DIO3 were both stimulated following formoterol administration (p < 0.05).ConclusionsThe results of our study support the groundwork for establishing further experiments utilizing exercise signaling as a clinical treatment in models targeting dysfunctional skeletal muscle cell growth.

Developmental toxicity and neurobehavioral effects of sodium selenite and selenium nanoparticles on zebrafish embryos

Selenium, a trace mineral, is essential for several physiological processes in humans and animals. It is an antioxidant vital for the immunological response, DNA synthesis, thyroid hormone metabolism, and antioxidant defense enzymes. Zebrafish embryos and larvae were exposed to different concentrations of sodium selenite (SodSe) and selenium nanoparticles (SeNs) at various developmental stages. The study evaluated the impact of SodSe and SeNs on larvae survival, hatching rate, and morphological abnormalities. Also, acridine orange staining was used to analyze the apoptotic cell death, and behavioral tests were conducted to assess anxiety-like behaviors. The results showed that both SodSe and SeNs influence the development and neurobehavior of zebrafish larvae in a concentration-dependent manner. SodSe at high concentration causes low survival rates, delayed hatching, and increased morphological defects in zebrafish larvae. In addition, exposure to SodSe resulted in elevated apoptosis in different larval tissues. Zebrafish larvae treated with SodSe and SeNs exhibited anxiety-like behaviour, increased thigmotaxis, less exploratory behaviour, and less swimming patterns. The nerve conductions and stimuli responses evaluated through acetylcholine esterase (AChE) and cortisol assays, revealed a decrease in the activity in a dose-dependent manner of SodSe and SeNs. Interestingly, the effects of SeNs were lower even at higher concentrations when compared with SodSe at lower concentrations on zebrafish embryos. This shows that SeNs synthesized through biological methods may be less toxic and may have lower effect on the development and neurobehavior of zebrafish larvae. Thus, our study confirms the cytotoxic and neurobehavioral effects of SodSe and suggests the use of SeNs at lower concentration to provide insights into better understanding of developmental stages and metabolic pathways in zebrafish larvae.

Deciphering the roles of triiodothyronine (T3) and thyroid-stimulating hormone (TSH) on cardiac electrical remodeling in clinical and experimental hypothyroidism.

Hypothyroidism is the most frequent endocrine pathology. Although clinical or overt hypothyroidism has been traditionally associated to low T3 / T4 and high thyrotropin (TSH) circulating levels, other forms exist such as subclinical hypothyroidism, characterized by normal blood T3 / T4 and high TSH. In its different forms is estimated to affect approximately 10% of the population, especially women, in a 5:1 ratio with respect to men. Among its consequences are alterations in cardiac electrical activity, especially in the repolarization phase, which is accompanied by an increased susceptibility to cardiac arrhythmias. Although these alterations have traditionally been attributed to thyroid hormone deficiency, recent studies, both clinical trials and experimental models, demonstrate a fundamental role of TSH in cardiac electrical remodeling. Thus, both metabolic thyroid hormones and TSH regulate cardiac ion channel expression in many and varied ways. This means that the different combinations of hormones that predominate in different types of hypothyroidism (overt, subclinic, primary, central) can generate different forms of cardiac electrical remodeling. These new findings are raising the relevant question of whether serum TSH reference ranges should be redefined.

Serum Copper, Iron, and Total Iron Binding Capacity in Hypothyroidism: A Case Control Study

Background: Thyroid hormone metabolism is linked to iron metabolism. Thyroperoxidase, a key enzyme in the biosynthesis of thyroid hormones, is iron-dependent. Thus, iron deficiency might be the primary cause of hypothyroidism. Copper is another trace element that has been linked to thyroid status. Copper regulates excessive thyroxine (T4) absorption and reduces cell damage during thyroid hormone synthesis. The present study clarified the possible correlations between iron and copper levels as well as total iron binding capacity (TIBC) and triiodothyronine (T3), T4, as well as thyroid-stimulating hormone (TSH) levels in healthy and hypothyroid subjects.Materials and methods: Thirty-five healthy subjects and 35 hypothyroid subjects were included in this study. Serum T3, T4, and TSH levels were measured using the enzyme linked fluorescence assay. Serum iron levels and TIBC were estimated using ferrozine/magnesium carbonate method, while serum copper levels were estimated using colorimetric method.Results: Copper levels were not significantly different between healthy and hypothyroid subjects. Iron and T4 levels were significantly lower in hypothyroid subjects compared with those in healthy subjects, while TIBC and TSH levels were significantly higher. There was no significant correlation between copper levels and T3, T4, and TSH levels.Conclusion: There were inverse correlations between TIBC and T4 as well as iron levels, and there was no significant correlation between copper levels and all thyroid function parameters. Routine examination of iron levels and thyroid function is highly recommended for early diagnosis and therapy of hypothyroidism.Keywords: total iron binding capacity, iron, copper, hypothyroidism

Thyroid hormone transport and metabolism are disturbed in the placental villi of miscarriage

BackgroundIt has been long known that thyroid hormone regulates placental villi development, which is associated with the occurrence of miscarriage. However, whether abnormal thyroid hormone metabolism and transport in placental villi are involved in miscarriage is still to be verified.MethodsPlacental villi of elective terminations of pregnancies (ETPs) and miscarriage were collected. Proliferative activity and apoptosis of villi trophoblasts and angiogenesis were detected by TUNEL and immunochemistry. The expressions of thyroid hormone receptors (THRs), transthyretin (TTR), monocarboxylate transporter 8 (MCT8), organic anion transporting polypeptides 1A1 (OATP1A1), deiodinase 2 (Dio2) and Dio3 were examined by RT-PCR, Western blot, immunohistochemistry and immunofluorescence. JEG3 cell was treated with iopanoic acid (IOP), an inhibitor of Dio2 activity, the expressions of Dio2, placenta growth factor (PLGF) and sFlt1 were detected by RT-PCR and Western blot.ResultsCell proliferation was suppressed and apoptosis was increased in placental villi cytotrophoblasts of miscarriage. CD34+ vessel number and vascular endothelial growth factor (VEGF) protein abundance were decreased in miscarriage. In miscarriage group, the gene expression of Dio2, Dio3, TTR and THRα, but not THRβ, MCT8 and OATP1A1, were downregulated. The protein abundances of TTR and THRα were downregulated in miscarriage group, but not THRβ. The protein abundance of Dio2 in miscarriage villi was decreased compared with that in ETP. In JEG3 cells, the gene expression of PLGF was decreased and the expression of sFlt1 was increased in IOP treatment; The protein abundance of Dio2 was downregulated but the gene expression of Dio2 was unaffected in IOP treatment.ConclusionThyroid hormone transport and metabolism in miscarriage were disturbed and may impaired angiogenesis of placental villi, which was associated with the occurrence of miscarriage.

"Alphabet" Selenoproteins: Implications in Pathology.

Selenoproteins are a group of proteins containing selenium in the form of selenocysteine (Sec, U) as the 21st amino acid coded in the genetic code. Their synthesis depends on dietary selenium uptake and a common set of cofactors. Selenoproteins accomplish diverse roles in the body and cell processes by acting, for example, as antioxidants, modulators of the immune function, and detoxification agents for heavy metals, other xenobiotics, and key compounds in thyroid hormone metabolism. Although the functions of all this protein family are still unknown, several disorders in their structure, activity, or expression have been described by researchers. They concluded that selenium or cofactors deficiency, on the one hand, or the polymorphism in selenoproteins genes and synthesis, on the other hand, are involved in a large variety of pathological conditions, including type 2 diabetes, cardiovascular, muscular, oncological, hepatic, endocrine, immuno-inflammatory, and neurodegenerative diseases. This review focuses on the specific roles of selenoproteins named after letters of the alphabet in medicine, which are less known than the rest, regarding their implications in the pathological processes of several prevalent diseases and disease prevention.

THU669 Time To Achieve Euthyroidism In Graves Disease Using Methimazole In An Urban Population

Abstract Disclosure: S.S. Habbsa: None. E. Yunasan: None. A. Krishnan: None. K.M. Munir: None. Context: Previous studies of treatment response in Graves disease have shown that that the mean time to reach euthyroidism with methimazole (MMI) was several weeks to months. In 1987 Okamura et al. concluded that the average period was 6-7 weeks with MMI 30mg daily. Nakamura et al. showed similar data in 2007 (5.8 +/- 4 weeks). These studies were performed in Japanese hospitals over 15 years ago. Limited data exists regarding treatment response times with different doses in a diverse urban population, which may vary with regards to typical dietary patterns, thyroid hormone metabolism and thionamide pharmacokinetics. Objective: The objective of this retrospective chart review was to determine the mean time to achieve euthyroidism with MMI in patients with newly diagnosed Graves disease in Baltimore City. Methods: Patients with Graves hyperthyroidism newly diagnosed in the last 5 years were identified from outpatient endocrine and primary care clinics within the University of Maryland Medical Center healthcare system. Time to achieve euthyroidism (from the start of thionamide therapy to date of euthyroid labs, defined as normal free T4 level) was assessed. Results: 128 patients with recently diagnosed Graves hyperthyroidism were identified (126 patients treated with MMI only and 2 with PTU only). 78% of subjects were female and the mean age at diagnosis was 47 years. The average daily dose of MMI ranged from 2.5mg to 60mg. On average, Free T4 decreased by 0.47 ng/dL per week. The mean time to achieve euthyroidism was 10.1 weeks (8.6, 11.6) overall, similar in males and females. On sub analysis, time to achieve euthyroidism was lower in younger males (age &amp;lt; 40 years) [6.6 weeks (3.9, 9.3)] and older females (age &amp;gt; 40 years) [8.3 (6.9, 9.7)]. Conclusion: The above data may inform expectations for treatment response for newly diagnosed Graves disease, specifically in an urban population on a Westernized diet. Patient forums have shown increasing interest in therapeutic alternatives to thionamides, including specialized diets. This data may help to determine whether other proposed therapies for initial treatment of Graves hyperthyroidism are more or less efficacious. Presentation: Thursday, June 15, 2023

FRI511 Bexarotene: A Deceptive Cause Of Iatrogenic Hypothyroidism

Abstract Disclosure: S. Ghaith: None. A. Ramachandran: None. C. Alcorn: None. F. Amer: None. A. Thompson: None. A. Ramachandran: None. Background: Bexarotene, an antineoplastic agent used for the treatment of cutaneous T cell lymphoma, is associated with a rapid and profound suppression of thyrotropin, which may lead to central hypothyroidism. Case: A Seventy-four-year-old female with a recent diagnosis of Cutaneous T cell lymphoma presented with a 1-week history of progressive fatigue, lightheadedness, and night sweats. She was found to have hypotension and hypothermia. She was started on oral Bexarotene chemotherapy 225 mg daily five days prior to admission. The physical exam was unremarkable except for sinus bradycardia and hypothermia. Labs were significant for TSH 0.48 [0.4-4.2 uIU/mL] dropped from 3.3 uIU/mL one week prior, FT4 0.5 [0.8-1.7 ng/dL] and Total T3 111 ng/dL [87- 187 ng/dL] consistent with central hypothyroidism. Bexarotene was held during her hospitalization per hematology recommendations. The patient was started on Levothyroxine 50 mcg, which was later advanced to 75 mcg daily based on free T4 levels. At one month follow up, free T4 level normalized while on Levothyroxine and Bexarotene was restarted again by her hematologist. Discussion: Bexarotene, an antineoplastic agent approved for treating cutaneous T cell lymphoma, can rapidly suppress TSH levels by directly inhibiting its secretion and affect thyroid hormone metabolism, leading to central hypothyroidism. The degree of suppression of TSH increases with higher doses of Bexarotene while reduction in free T4 and TSH are reversible. Patients already receiving thyroid hormone therapy may require increased thyroid hormone doses to achieve therapeutic levels. If bexarotene is permanently discontinued, levothyroxine can either be stopped or can be resumed to doses used prior to bexarotene therapy. Recovery of thyroid function usually occurs within weeks of Bexarotene discontinuation. Conclusion: Oral Bexarotene can cause central hypothyroidism therefore, thyroid function tests should be measured at baseline and treatment. Thyroid hormone replacement should be considered if central hypothyroidism is suspected. Presentation: Friday, June 16, 2023

SAT473 First Case Of Diffuse Thyroid Lipomatosis With Amyloid Deposits Presenting With Hyperthyroidism

Abstract Disclosure: A.M. Gonzalez Gil: None. M.A. Ruiz Santillan: None. H. Quadri: None. B.K. Force: None. R. Gaba: None. Background: Diffuse thyroid lipomatosis (DTL) is an exceedingly rare entity of unknown etiology which can be associated with amyloidosis. It generally presents with euthyroidism but very few cases with hyperthyroidism have been reported. Clinical Case: A 64-year-old woman from Pakistan with a several-year history of a non-tender goiter presented to the emergency department with an upper respiratory and gastrointestinal viral syndrome in the context of several weeks of progressively worsening fatigue. She also reported unintentional weight loss over several years. She denied other hyperthyroid or compressive symptoms. Her exam was notable for resting sinus tachycardia and an approximately 100 gm painless goiter. Laboratory evaluation was notable for a markedly elevated creatinine with nephrotic range proteinuria. She was declared to have end stage renal disease (ESRD) and hemodialysis was initiated. She was also found to have a suppressed TSH (&amp;lt;0.01 uIU/mL, NR=0.45-5.33) and elevated FT4 (2.17 ng/dl, NR=0.64-1.42). Total T3 was low (42 ng/dl, NR=87-178), which was attributed to hypoalbuminemia and altered peripheral thyroid hormone metabolism with underlying ESRD. Further evaluation revealed elevated ESR, CRP and thyroglobulin levels (625.9 ng/mL, NR=1.5-38.5), while thyroid stimulating immunoglobulin, thyroid receptor antibodies and thyroid peroxidase antibodies were undetectable. A thyroid ultrasound revealed an enlarged fatty thyroid consistent with DTL. A radioactive iodine uptake scan revealed normal 24-hour uptake (14.1%, NR=7-32%) in a slightly heterogeneous thyroid with no aberrant functioning thyroid tissue. She was started on atenolol, with significant improvement in her tachycardia, but her FT4 continued to increase. Methimazole was initiated. Dose uptitration and administration after dialysis resulted in near-normalization of FT4 levels. She subsequently underwent renal and thyroid biopsies, both of which showed apple green birefringence under polarized light with Congo Red stain, indicating amyloidosis. Core thyroid biopsy additionally showed benign adipose tissue with entrapped thyroid follicles, confirming concomitant DTL. Although other authors have found thyroid amyloid deposits in DTL, and yet others have reported hyperthyroidism in DTL without amyloidosis, this is the first reported case of hyperthyroidism in a patient with DTL with amyloid deposits. Interestingly, chronic hypoxia in amyloid goiters has been hypothesized to cause fibroblast-to-adipocyte metaplasia leading to DTL. We speculate that excess thyroid hormone release could also be mediated by follicular cells’ response to hypoxia induced by amyloid and fatty infiltration of the thyroid. Conclusion: To the best of our knowledge, this is the first reported case of diffuse thyroid lipomatosis with amyloid deposits to be associated with concurrent hyperthyroidism. Presentation Date: Saturday, June 17, 2023