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Regardless of the cause, hypothyroidism should be treated with levothyroxine. The objectives of management are the normalization of TSH levels and the relief of symptoms. In general, the vast majority of patients who achieve normalization of TSH levels show a resolution of symptoms; however, for a small number of individuals, symptoms persist (despite adequate control of TSH). This scenario generates a dilemma in the therapeutic approach to these patients, because even when excluding other causes or concomitant diseases that can explain the persistence of symptoms, pharmacological management strategies are scarce. Consequently, the efficacy of some less conventional approaches to therapy, such as the use of LT3 monotherapy, desiccated thyroid extracts, and LT4/LT3 combinations, in addressing persistent hypothyroid symptoms have been evaluated in multiple studies. The majority of these studies did not observe a significant benefit from these "nonconventional" therapies in comparison to results with LT4 monotherapy alone. Nevertheless, some studies report that a significant proportion of patients prefer an alternative to monotherapy with LT4. The most common approach has been to prescribe a combination of LT4 and LT3, and this review describes and analyzes the current evidence of the efficacy of LT4/LT3 combination therapy vs. LT4 monotherapy in addressing persistent hypothyroidism symptoms to provide suggested guidelines for clinicians in the management of these patients.

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Hypothyroidism is a prevalent thyroid condition in which the thyroid gland fails to secrete an adequate amount of thyroid hormone into the bloodstream. This condition may develop due to genetic or acquired factors. The most frequent cause of acquired hypothyroidism is chronic autoimmune thyroiditis, also known as Hashimoto's disease. Acquired hypothyroidism is diagnosed when patients present with overt hypothyroidism (also known as clinical hypothyroidism), as they exhibit increased TSH and decreased T3 and T4 serum levels. This article examines the prevalence of psychiatric disorders among patients diagnosed with acquired hypothyroidism with or without Levothyroxine treatment. We discuss the available evidence indicating that acquired hypothyroidism may be a risk factor for psychiatric disorders, and the effectiveness of thyroid treatment in relieving psychiatric symptoms. Additionally, we provide critical details on thyroid hormone cutoff values reported in the literature, their potential clinical importance, and their correlation with psychiatric symptoms. Finally, we examined the various mechanisms by which acquired hypothyroidism can lead to depression. The high rate of comorbidity between hypothyroidism and psychiatric disorders deserves special attention, indicating the importance of consistent monitoring and timely identification of psychiatric symptoms to prevent disease exacerbation and facilitate therapeutic management. On the other hand, several mechanisms underlie the strong association between depression and acquired hypothyroidism. Deeper research into these mechanisms will allow knowledge of the pathophysiology of depression in patients with acquired hypothyroidism and will provide clues to design more precise therapeutic strategies for these patients.

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CONTEXT: Thyroid-stimulating hormone (TSH) trajectory classification represents a novel approach to defining the adequacy of levothyroxine (LT4) treatment for hypothyroidism over time. OBJECTIVE: This is a proof of principle study that uses longitudinal clinical data, including thyroid hormone levels from a large prospective study to define classes of TSH trajectories and examine changes in cardiovascular (CV) health markers over the study period. METHODS: Growth mixture modeling (GMM), including latent class growth analysis (LCGA), was used to classify LT4-treated individuals participating in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) based on serial TSH levels. Repeated measure analyses were then utilized to assess within-class changes in blood pressure, lipid levels, hemoglobin A1c, and CV-related medication utilization. RESULTS: From the 621 LT4-treated study participants, the best-fit GMM approach identified 4 TSH trajectory classes, as defined by their relationship to the normal TSH range: (1) high-high normal TSH, (2) normal TSH, (3) normal to low TSH, and (4) low to normal TSH. Notably, the average baseline LT4 dose was lowest in the high-high normal TSH group (77.7 µg, P < .001). There were no significant differences in CV health markers between the classes at baseline. At least 1 significant difference in CV markers occurred in all classes, highlighted by the low to normal class, in which total and high-density lipoprotein cholesterol, triglycerides, and A1c all increased significantly (P = .049, P < .001, P < .001, and P = .001, respectively). Utilization of antihypertensive, antihyperlipidemic, and antidiabetes medications increased in all classes. CONCLUSION: GMM/LCGA represents a viable approach to define and examine LT4 treatment by TSH trajectory. More comprehensive datasets should allow for more complex trajectory modeling and analysis of clinical outcome differences between trajectory classes.

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CONTEXT: The effectiveness of levothyroxine (LT4) in restoring thyroid hormone (TH) homeostasis, particularly serum thyroxine (T4) and triiodothyronine (T3) levels, remains debatable. OBJECTIVE: This work aimed to assess TH homeostasis in LT4-treated individuals using data from the Longitudinal Study of Adult Health in Brazil (ELSA-Brasil) study. METHODS: The ELSA-Brasil study follows 15 105 adult Brazilians (aged 35-74 years) over 8.2 years (2008-2019) with 3 observation points assessing health parameters including serum thyrotropin (TSH), free T4 (FT4), and free T3 (FT3) levels. We analyzed 186 participants that initiated treatment with LT4 during the study, and 243 individuals continuously treated with LT4 therapy. RESULTS: Initiation of therapy with LT4 resulted in an 11% to 19% decrease in TSH, an approximately 19% increase in FT4, and a 7% reduction in FT3 serum levels (FT3 dropped >10% in ∼40% of the LT4-treated patients). This was associated with an increase in triglyceride levels and utilization of hypolipidemic and antidiabetic medications. Participants continuously treated with LT4 exhibited a stable elevation in serum FT4 and a reduction in serum FT3 and TSH levels. While 115 participants (47.3%) had at least 1 serum FT4 levels above the control reference range (>1.52 ng/dL), 38 participants (15.6%) had at least 1 serum FT3 below the reference range (<0.23 ng/dL). CONCLUSION: The present results challenge the dogma that treatment with LT4 for hypothyroidism restores TH homeostasis in all patients. A substantial number of LT4-treated patients exhibit repeated FT4 and FT3 levels outside the normal reference range, despite normal TSH levels. Further studies are needed to define the clinical implications of these findings.

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INTRODUCTION: This systematic review aimed to compare the effect of alternative levothyroxine administration regimens on thyroid hormone levels and patient-reported outcomes (PROs) among adults with hypothyroidism. METHODS: We searched PubMed, Embase, CENTRAL, CINAHL, LILACS, SciELO, Scopus, Web of Science, OpenGrey, ProQuest, ClinicalTrials.gov, and ICTRP from inception to May/2023 for randomized controlled trials (RCTs). We assessed the risk of bias with Cochrane Risk of Bias 2.0 tool. We analyzed TSH levels by pairwise and network meta-analyses (NMA). The FT4 levels and PROs were qualitatively assessed. RESULTS: We included 14 RCTs (906 participants) comparing different regimens, as bedtime vs. before breakfast. A total of 12 RCTs were at high risk of bias. Seven RCTs were included in the TSH meta-analysis, where the mean difference (MD) and 95% confidence interval (CI) were as follows: bedtime vs before breakfast (4 RCTs) 0.69 (-1.67-3.04), I2 = 92%, very low certainty evidence; weekly dose vs before breakfast (2 RCTs) 1.68 (0.94-2.41), I2 = 0%, low certainty evidence; and at breakfast vs before breakfast (1 RCT) 0.65 (-1.11-2.41), very low certainty evidence. The NMA showed no evidence of differences in TSH level with different regimens. CONCLUSION: The evidence is insufficient to determine the most effective levothyroxine administration regimen for hypothyroidism. SYSTEMATIC REVIEW REGISTRATION: PROSPERO - CRD42021279375.

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We report a two-month-old male cat weighing 630 grams with congenital hypothyroidism. The main complaints were difficulty defecating for more than three days and prostration. Physical examination revealed a broad, flat face, a short neck, enlarged submandibular lymph nodes, chemosis, mild bilateral mucopurulent ocular discharge, seborrheic coat, with gingival thickening around the upper and lower deciduous incisor teeth with partial eruption. The abdomen was distended due to constipation and right unilateral cryptorchidism. Based on this, feline congenital hypothyroidism was suspected. Hormonal tests (free T4 by equilibrium dialysis of 0.06 ng/dl, total T4 of 0.1 ng/ml and TSH of 4.7 ng/ml) confirmed this. Treatment was started with levothyroxine sodium (5-32.2 µg/kg/day). After 120 days of treatment, there was clinical stabilization. Then the patient underwent orchiectomy of the left and of the right ectopic testicles, and at 380 days of treatment, the thyroid scintigraphy showed intense uptake of the radiopharmaceutical by both thyroid lobes and a significant increase in volume. Clinical evaluation showed weight gain (2.6 kilograms during treatment), improvement in the shape of the skull, and a notable increase in body size. At 17 months of age, hormone values were within the reference limits after administration of levothyroxine sodium (32.2µg/kg/day).

O objetivo deste trabalho foi relatar o caso de hipotireoidismo congênito em um felino, macho, pelo curto brasileiro (PCB), com dois meses de idade, pesando 630 gramas. Apresentava como queixa principal dificuldade para defecar por mais de três dias e prostração. O exame físico geral constatou face larga e plana, pescoço curto, linfonodos submandibulares aumentados, quemose e discreta secreção ocular mucopurulenta bilateral. A pelagem apresentava-se opaca e seborreica, espessamento gengival em torno dos dentes decíduos incisivos superiores e inferiores com parcial erupção. À palpação, o abdômen apresentava-se distendido pela presença de fezes em cólon e criptorquidismo unilateral direito. Diante das alterações supracitadas, suspeitou-se de hipotireoidismo congênito felino. O qual foi confirmado através de exames complementares hormonais específicos (T4 livre por diálise do equilíbrio 0,06 ng/dl, T4 total 0,1 ng/ml e TSH 4,7 ng/ml). Iniciou-se o tratamento com levotiroxina sódica na dose de 5 a 32,2µg/kg/dia. Com 120 dias de tratamento houve estabilização clínica e então o paciente foi submetido à orquiectomia dos testículos esquerdo ectópico e direito. E aos 380 dias de tratamento ao exame de cintilografia de tireoide onde foi evidenciado intensa captação do radiofármaco por ambos os lobos tireoidianos e importante aumento de volume. Na avaliação clínica, foi observado ganho de peso (2,6 quilogramas ao longo do tratamento), melhora na conformação do crânio e notável aumento de tamanho corporal. Aos 17 meses de idade, os valores hormonais se encontravam dentro dos limites de referência, após a administração da dose de lexotiroxina sódica na dose de 32,2µg/kg/dia.

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PURPOSE: Inconsistencies in the medical management of hypothyroidism have been reported between endocrinologists in different countries. This study aimed to identify the attitudes of Latin America thyroid specialists towards the use of thyroid hormones. METHODS: Online survey of members of the Latin America Thyroid Society. RESULTS: 81/446 (18.2%) completed the questionnaire. Levothyroxine (LT4) was the initial treatment of choice for all respondents. 56.8% would consider LT4 use in biochemically euthyroid patients: infertile women with elevated anti-thyroid antibodies (46.9%), resistant depression (17.3%) and growing goiter (12%). Most respondents preferred tablets (39.5%) over liquid formulations (21.0%) or soft gel capsules (22.2%) and would not consider switching formulations in patients with persistent symptoms. 39.5% would never use LT4 + liothyronine (LT3) combination therapy in symptomatic euthyroid patients, due to low quality evidence for benefit. 60.5% reported that persistence of symptoms despite normal TSH is rare (below 5% of patients) and its prevalence has been stable over the last five years. Psychosocial factors (84.0%), comorbidities (86.4%) and the patient unrealistic expectation (72.8%) were considered the top three explanations for this phenomenon. CONCLUSION: LT4 tablets is the treatment of choice for hypothyroidism. A significant proportion of respondents would use LT4 in some groups of euthyroid individuals, contrasting the recommendations of the major clinical practice guideline indications. LT4 + LT3 combination treatment in euthyroid symptomatic patients was considered by nearly 50%. Practices based on weak or absent evidence included use of thyroid hormones for euthyroid subjects by 56.8% of respondents and use of LT4 + LT3 treatment by 60.5% of respondents for patients with persistent symptoms. In contrast to many European countries, LATS respondents report a low and unchanged proportion of dissatisfied patients over the last five years.

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Hypothyroidism can usually be treated effectively with oral levothyroxine (LT-4) supplementation. However, hypothyroidism refractory to treatment with LT-4 is a common clinical condition. Causes include poor compliance, interactions with food or other medications, and gastrointestinal diseases, such as inflammatory bowel disease and short bowel syndromes. Increasing the oral dose of LT-4 is not always effective in these scenarios. Therefore, other routes of administration may be necessary. In this report, we evaluate alternative treatment modalities for refractory hypothyroidism and present two patients with intestinal malabsorption successfully treated by subcutaneous administration of LT-4.

El hipotiroidismo generalmente se puede tratar de manera efectiva con levotiroxina (LT-4) oral. Sin embargo, el hipotiroidismo refractario al tratamiento con LT-4 es una condición clínica frecuente. Entre las causas se encuentra la falta de adherencia, interacciones con alimentos u otros medicamentos y enfermedades gastrointestinales, como enfermedad inflamatoria intestinal y síndromes de intestino corto. El aumento de la dosis oral de LT-4 no siempre es eficaz en estos escenarios. Por lo tanto, pueden ser necesarias otras vías de administración. En este reporte, evaluamos modalidades alternativas de tratamiento para el hipotiroidismo refractario y presentamos dos pacientes con malabsorción intestinal tratadas con éxito mediante la administración subcutánea de LT-4.

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Background: GlycA is a novel glycoprotein biomarker of systemic inflammation and cardiovascular risk. Our objective was to assess the levels of GlycA in individuals with hypothyroidism. We also explored whether levothyroxine (LT4)-treated patients had different levels of GlycA, with attention to thyrotropin (TSH) levels. Methods: We performed a cross-sectional analysis, using baseline data from the ELSA-Brasil cohort study. We included only participants with serum TSH and GlycA levels measurements, using magnetic resonance spectroscopy (n = 4745). We excluded individuals with endogenous hyperthyroidism and those using drugs impacting thyroid function. Participants not taking LT4 and whose serum TSH was 0.4-4.0 mIU/L were classified as euthyroid (EU) and those with elevated TSH as undiagnosed hypothyroidism (UH). For those on LT4 (n = 345), adequacy of treatment was defined as TSH within the reference range. Those with TSH <0.4 mIU/L were considered over-treated (OT), and those >4.0 mIU/L, under-treated (UT). Both (UT+OT) were considered inadequately treated (IT). Group comparisons were performed by Kruskal-Wallis, adjusted Chi-square, and the post hoc Dunn test. Additional subgroup analysis were performed in patients with circulating thyroperoxidase antibodies (TPO-Ab+). Respective multivariable analyses were performed to evaluate the relationship between thyroid-related variables and GlycA levels (Generalized Linear Model), as well as an abnormal GlycA (>400 µmol/L; Logistic Binary Regression). Results: The prevalence rate of UH was 9.8% (467/4745) and, among those on LT4, only 61.7% (213/345) were adequately treated (AT). GlycA levels were higher in IT in comparison to EU (429 vs. 410 µmol/L, p < 0.01) but did not differ between UH (413 µmol/L) and euthyroidism. However, the subgroup analysis of those TPO-Ab+ showed that not only those with IT, but also those with UH, had higher levels of GlycA in comparison to euthyroidism (423 and 424 vs. 402 µmol/L, p = 0.04). This association between higher levels of GlycA and IT was maintained even in multivariable analysis (odds ratio 1.53, confidence interval 1.03 to 2.31) Lower levels of GlycA were detected in AT (405 µmol/L,) compared with OT (432 µmol/L, 0.04) and UT (423 µmol/L, p = 0.02). Conclusions: Patients with IT, both OT and UT, had higher GlycA levels, which may be associated with low-grade systemic inflammation and, possibly, increased cardiovascular risk.

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The identification of factors that affect cannabidiol (CBD) systemic exposure may aid in optimizing treatment efficacy and safety in clinical practice. In this study, we aimed to correlate CBD plasma concentrations at a steady state to demographic, clinical, and pharmacological characteristics as well as seizure frequency after the administration of a purified CBD oil solution in a real-world setting of children with drug-resistant developmental and epileptic encephalopathies (DEEs). Patients receiving oral CBD pharmaceutical products at maintenance were enrolled. Venous blood samples were drawn before the CBD morning dose, 12 h apart from the last evening dose (C0 or CBD trough concentration). A linear mixed-effect analysis was implemented to assess the correlation between C0 and clinical, laboratory, pharmacological, and lifestyle factors. Fifteen females and seven males with a median age of 12.8 years (ranging between 4.7 and 17.2) were included. The median CBD dose was 8.8 mg/kg/day (ranging between 2.6 and 22.5), and the CBD C0 median (range) was 48.2 ng/mL (3.5-366.3). The multivariate model showed a 109.6% increase in CBD C0 in patients with concomitant levothyroxine (ß = 0.74 ± 0.1649, p < 0.001), 56.8% with food (ß = 0.45 ± 0.1550, p < 0.01), and 116.0% after intake of a ketogenic diet (ß = 0.77 ± 0.3141, p < 0.05). All patients included were responders without evidence of an association between C0 and response status. In children with DEEs, systemic concentrations of CBD may be significantly increased when co-administered with levothyroxine, food, or a ketogenic diet.

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Resumen El hipotiroidismo generalmente se puede tratar de manera efectiva con levotiroxina (LT-4) oral. Sin em bargo, el hipotiroidismo refractario al tratamiento con LT-4 es una condición clínica frecuente. Entre las causas se encuentra la falta de adherencia, interacciones con alimentos u otros medicamentos y enfermedades gas trointestinales, como enfermedad inflamatoria intestinal y síndromes de intestino corto. El aumento de la dosis oral de LT-4 no siempre es eficaz en estos escenarios. Por lo tanto, pueden ser necesarias otras vías de administración. En este reporte, evaluamos modalidades alternativas de tratamiento para el hipotiroidismo re fractario y presentamos dos pacientes con malabsorción intestinal tratadas con éxito mediante la administración subcutánea de LT-4.

Abstract Hypothyroidism can usually be treated effectively with oral levothyroxine (LT-4) supplementation. However, hypothyroidism refractory to treatment with LT-4 is a common clinical condition. Causes include poor com pliance, interactions with food or other medications, and gastrointestinal diseases, such as inflammatory bowel disease and short bowel syndromes. Increasing the oral dose of LT-4 is not always effective in these scenarios. Therefore, other routes of administration may be neces sary. In this report, we evaluate alternative treatment modalities for refractory hypothyroidism and present two patients with intestinal malabsorption successfully treated by subcutaneous administration of LT-4.

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BACKGROUND: Fatigue is a common symptom in hypothyroidism; however, the effect of levothyroxine on fatigue has been little studied. The aim of this study was to evaluate the effect of levothyroxine on fatigue in Latino patients with primary hypothyroidism, as well as the association of TSH and free T4 (FT4) with the severity and persistence of fatigue. METHODS: A prospective study was performed in 92 patients with primary hypothyroidism. Fatigue severity scale (FSS) scores and clinical and biochemical characteristics before and at 6 months of levothyroxine were evaluated. RESULTS: After 6 months of levothyroxine, a reduction in FSS (53 (47-57) vs. 36 (16-38); p = 0.001) and fatigue frequency (45.7% vs. 26.1%; p = 0.008) was evident. Both before and after 6 months of levothyroxine, there was a positive correlation of the FSS score with TSH and a negative correlation with FT4. Persistent fatigue was associated with a pretreatment FSS score (r = 0.75; p = 0.001) and diabetes (r = 0.40; p = 0.001). An FSS > 34 (RR 3.9 (95% CI 1.43-10.73; p = 0.008)), an FSS > 36 (RR 3.23 (95% CI 1.21-8.6; p = 0.019)), and diabetes (RR 5.7 (95% CI 1.25-9.6; p = 0.024)) before treatment were risk factors for persistent fatigue. CONCLUSIONS: Levothyroxine improved fatigue in most patients. Diabetes and an FSS score >34 or >36 before treatment were risk factors for persistent fatigue.

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Introducción: El hipotiroidismo es una entidad de visita frecuente al endocrinólogo, establecer el mejor tratamiento es un desafío, a pesar del manejo adecuado y de un control hormonal óptimo, en ocasiones los pacientes continúan con los síntomas que afectan su calidad de vida, por lo que el tratamiento debe ser individualizado, basado en la mejor evidencia. Objetivo: Establecer las mejores opciones terapéuticas en las diferentes formas de presentación del hipotiroidismo. Métodos: Se realizó una búsqueda bibliográfica no sistemática en las bases de datos de PubMed, Medline, LILACS, EMBASE, Redalyc y guías internacionales. Los criterios de inclusión fueron publicaciones en inglés y español, en las que el título, palabras clave o resumen incluyen información pertinente al objetivo de estudio, periodicidad no mayor a los 5 años a excepción de las guías que son las últimas revisiones. En la búsqueda se obtuvieron 30 artículos de los cuales fueron 14 seleccionados. Conclusiones: Se establecieron las opciones terapéuticas con el fin de obtener un mejor tratamiento para el paciente hipotiroideo que debe ser individualizado y basado en la mejor evidencia, para alcanzar un control adecuado de su enfermedad, mejorar la calidad de vida y evitar complicaciones relacionadas con esta patología(AU)

Introduction: Hypothyroidism is an entity that is frequently seen at the endocrinologist´s. establishing the best treatment is a challenge, despite proper management and optimal hormonal control, sometimes patients continue with symptoms which affect their quality of life, therefore that treatment should be individualized, based on the best evidence. Objective: To establish the best therapeutic options in hypothyroidism different forms of presentation. Methods: A non-systematic bibliographic search was carried out in PubMed, Medline, LILACS, EMBASE, Redalyc databases and in the international guidelines. The inclusion criteria were publications in English and Spanish, in which the title, keywords or abstract include relevant information to the objective of the study, with a periodicity of no more than 5 years, except for the guidelines that the latest revisions were used. In the search, 30 articles were retrieved, 14 which were selected. Conclusions: The therapeutic options were established in order to find better treatment for hypothyroid patients, which must be individualized and based on the best evidence, to achieve adequate control of the disease, to improve the quality of life and to avoid related complications(AU)

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INTRODUCTION: The history of levothyroxine has been linked to advances in the treatment of thyroid disease and to date it is the standard therapy for the treatment of hypothyroidism. Bioequivalence studies are the most widely used method to demonstrate interchangeability, although controversy persists regarding the best design for this molecule declared as a narrow therapeutic index product in many countries. This study aimed to evaluate the pharmacokinetic profile of two formulations of levothyroxine to determine bioequivalence between them. METHODS: This two-period, randomized, crossover, blind study was conducted in 80 healthy volunteers, of both sexes, using a single levothyroxine dose of 600 µg with a washout period of 42 days. Blood sampling was performed at - 30 min, - 15 min, and 0 h pre-dose and 30 min, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 10, 12, 16, 24, and 48 h post-dose. RESULTS: A total of 78 subjects successfully completed both periods. There were no serious adverse events during the study and both formulations were well tolerated. Baseline correction of serum levothyroxine concentrations was performed before statistical analysis. The mean maximum plasma concentration of the test product (Levotiroxina MK®) was 57.49 ng/mL while for the reference product it reached 59.32 ng/mL. Importantly, both test and reference formulations reached maximum concentrations in plasma at about the same time. The areas under the pharmacokinetic curves with the test product showed AUC0-t of 1407.1 ng h/mL and the reference product 1394.3 ng h/mL. The bioequivalence statistical analysis showed that the 90% confidence interval (CI90%) of the ratio of test over reference formulation was within the bioequivalence margins of 90-111%. For Cmax, the test/reference ratio was 96.2% with CI90% of 91.6-100.9%, and for AUC0-t the test/reference ratio was 99.9 with CI90% of 93.3-107.0%. CONCLUSIONS: Both formulations have the same pharmacokinetic profile and are bioequivalent in the narrow therapeutic index required by some health authorities.

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Suppressive levothyroxine therapy (sT4) is a cornerstone in the management of differentiated thyroid cancer (DTC). Long-term sT4 may affect bone mineral density (BMD). We evaluated the effect of sT4 on the bone mass of young DTC patients. In this cross-sectional study, BMD was evaluated via dual-energy X-ray absorptiometry in DTC patients younger than 25 years at diagnosis and undergoing sT4 for ≥1 year. The two control groups comprised patients matched for sex, age, and body-mass-index who were thyroidectomized for indications other than DTC and undergoing L-T4-replacement therapy, and healthy individuals with no prior known thyroid disease. Ninety-three participants were included (thirty-one in each group). There were no differences in the mean age, female sex (77.4% in all groups), or BMI between the sT4 group and each control group. The median TSH level was lower (0.4 [0.04-6.5] vs. 2.7 [0.8-8.5] mIU/mL, p = 0.01) and the mean L-T4 mcg/Kg levels were higher (2.4 ± 0.6 vs. 1.6 ± 0.3, p = 0.01) in the sT4 group compared to the L-T4-replacement therapy group. Lumbar spine, femoral neck, and total femur BMD were all similar among the groups. sT4 does not impact BMD in young DTC patients after a median time of suppression of 8 years. These findings may help in the decision-making and risk/benefit evaluation of sT4 for this population.

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INTRODUCTION: Although, it is generally held that the levothyroxine (LT4) dose tends to decrease with age, this theory remains controversial. Our objective was to assess whether the LT4 dose required to achieve euthyroid status varies according to age, body weight (BW), sex, menopausal status, or antibody status. MATERIALS AND METHODS: A cross-sectional study was performed from the retrospective review of the charts of patients with a previous diagnosis of primary hypothyroidism in treatment with LT4 and in a euthyroid state. Sex, age, actual body weight (ABW), TSH, and LT4 dose were recorded. Patients were grouped according to age ranges (18-44, 45-65, and over 65 years). A euthyroid state was defined as a serum TSH within the range of 0.4-4µIU/ml. A multiple linear regression model was performed to assess the LT4 dose and age, gender, antibody status, and ABW. RESULTS: A total of 882 charts of patients were reviewed. 586 patients met the inclusion criteria. The median age was 55 years. There was no correlation between the LT4 dose and age. A positive correlation was observed between the LT4 dose and ABW, but not with the ideal BW. Linear regression analysis showed that positivity antibody and ABW have a significant effect on the LT4 dose. Comparison of the LT4 dose between the different age groups showed no difference. CONCLUSION: Our study demonstrates that the dose of LT4 necessary to achieve euthyroidism is influenced by ABW and the presence of antibodies. Age and menopause did not influence the required daily dose of LT4.

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Hypothyroidism is an endocrine disorder whose management raises many challenges in clinical practice. Its standard treatment is levothyroxine (LT4). The goal of the treatment is to normalize signs and symptoms, as well as to achieve thyroid-stimulating hormone (TSH) concentrations within the reference range, on an individual basis. It is known that 5-10% of hypothyroid patients remain symptomatic, despite achieving the target TSH levels, which, in turn, affects their quality of life. After ruling out other causes of non-thyroid origin for this persistence, it is suggested that these patients could benefit from the use of liothyronine (LT3), added to LT4, especially if polymorphism of the deiodinase 2 (D2) genes is documented. There exist a variety of LT3 preparations, whose concentrations vary from 5 to 50 ug, with the recommended LT4/LT3 ratio of 13:1-20:1. The goals of combination therapy should be to achieve a physiological ratio of free triiodothyronine/free thyroxine (FT3/FT4) and non-suppression of TSH. Because there is currently no guide that makes evidence-based recommendations on the use of LT3 in primary hypothyroidism, more clinical studies are needed to be able to identify hypothyroid patients who may benefit from the use of LT3, by identifying new biomarkers.

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The purpose of this paper was to systematically summarize the published literature on neonatal isolated hyperthyrotropinemia (HTT), with a focus on prevalence, L-T4 management, re-evaluation of thyroid function during infancy or childhood, etiology including genetic variation, thyroid imaging tests, and developmental outcome. Electronic and manual searches were conducted for relevant publications, and a total of 46 articles were included in this systematic review. The overall prevalence of neonatal HTT was estimated at 0.06%. The occurrence of abnormal imaging tests was found to be higher in the persistent than in the transient condition. A continuous spectrum of thyroid impairment severity can occur because of genetic factors, environmental factors, or a combination of the two. Excessive or insufficient iodine levels were found in 46% and 16% of infants, respectively. Thirty-five different genetic variants have been found in three genes in 37 patients with neonatal HTT of different ethnic backgrounds extracted from studies with variable design. In general, genetic variants reported in the TSHR gene, the most auspicious candidate gene for HTT, may explain the phenotype of the patients. Many practitioners elect to treat infants with HTT to prevent any possible adverse developmental effects. Most patients with thyroid abnormalities and/or carrying monoallelic or biallelic genetic variants have received L-T4 treatment. For all those neonates on treatment with L-T4, it is essential to ensure follow-up until 2 or 3 years of age and to conduct medically supervised trial-off therapy when warranted. TSH levels were found to be elevated following cessation of therapy in 44% of children. Withdrawal of treatment was judged as unsuccessful, and medication was restarted, in 78% of cases. Finally, data extracted from nine studies showed that none of the 94 included patients proved to have a poor developmental outcome (0/94). Among subjects presenting with normal cognitive performance, 82% of cases have received L-T4 therapy. Until now, the precise neurodevelopmental risks posed by mild disease remain uncertain.

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INTRODUCTION: Although, it is generally held that the levothyroxine (LT4) dose tends to decrease with age, this theory remains controversial. Our objective was to assess whether the LT4 dose required to achieve euthyroid status varies according to age, body weight (BW), sex, menopausal status, or antibody status. MATERIALS AND METHODS: A cross-sectional study was performed from the retrospective review of the charts of patients with a previous diagnosis of primary hypothyroidism in treatment with LT4 and in a euthyroid state. Sex, age, actual body weight (ABW), TSH, and LT4 dose were recorded. Patients were grouped according to age ranges (18-44, 45-65, and over 65 years). A euthyroid state was defined as a serum TSH within the range of 0.4-4µIU/ml. A multiple linear regression model was performed to assess the LT4 dose and age, gender, antibody status, and ABW. RESULTS: A total of 882 charts of patients were reviewed. 586 patients met the inclusion criteria. The median age was 55 years. There was no correlation between the LT4 dose and age. A positive correlation was observed between the LT4 dose and ABW, but not with the ideal BW. Linear regression analysis showed that positivity antibody and ABW have a significant effect on the LT4 dose. Comparison of the LT4 dose between the different age groups showed no difference. CONCLUSION: Our study demonstrates that the dose of LT4 necessary to achieve euthyroidism is influenced by ABW and the presence of antibodies. Age and menopause did not influence the required daily dose of LT4.

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ABSTRACT Subclinical hypothyroidism (Shypo) is an increasingly frequent condition in common medical practice. Its diagnosis continues to pose a challenge since a series of non-thyroidal and temporary conditions can elevate serum TSH levels. In addition, the consequences of Shypo are still up for debate. Although detrimental cardiovascular effects have been consistently demonstrated in the young, they are less evident in older adults (65-79 years), and even more so in the oldest old (≥80 years). In the absence of evidence of any benefits of treating Shypo in patients' clinical manifestations and unfavorable outcomes, the most effective decision-making approach should include a thorough investigation of the patient's condition integrating all relevant clinical data, such as TSH levels, age, quality of life, comorbidities, cardiovascular risk, safety, and personal preferences. The decision-making process needs to take into account the risk of levothyroxine overtreatment and the resulting adverse consequences, such as reduction of bone mineral density, heart failure, and atrial fibrillation. Hence, current evidence suggests that individuals with TSH > 10 mU/L, who test positive for TPO Ab or are symptomatic may benefit from levothyroxine treatment. However, a more cautious and conservative approach is required in older (≥65 years of age), and oldest-old (≥80 years) patients, particularly those with frailty, in which the risk of treatment can outweigh potential benefits. The latter may benefit from a wait-and-see approach.

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