Therapeutic challenges in the application of serum thyroid stimulating hormone testing in the management of patients with hypothyroidism on replacement thyroid hormone therapy: a review

Importance of right communication with healthcare providers and patients about the new levothyroxine formulation: an expert opinion from Asia Pacific Thyroid Advisory Board

Levothyroxine (LT4), being "narrow therapeutic index" drug, may lead to significant fluctuations in thyroid stimulating hormone (TSH) levels. Such fluctuations can result in clinically noteworthy disruptions in thyroid function and give rise to adverse clinical consequences. Consequently, regulatory standards for LT4 potency have been tightened, with the most stringent specifications requiring maintenance of potency within the range of 95-105% of the labeled dose throughout the entire shelf-life of the product. The LT4 new formulation with tightened specification adheres to these rigorous standards, demonstrating established bioequivalence to its older formulation while upholding an equivalent standard of safety and efficacy. Furthermore, the novel formulation exhibits enhanced stability and an extended shelf-life. Of paramount significance is its capacity to provide patients with accurate and consistent dosing, thereby effectively catering to their medical requirements. The primary objective of the Asia-Pacific advisory board meeting (held in June 2022 with endocrinologists, experts from India, Indonesia, Philippines, Thailand, Malaysia and Singapore) was to establish the importance of appropriate communication to HCPs, patients and other stakeholders regarding the LT4 new formulation. The aim of this brief review is to highlight the importance of communication with healthcare professionals that should focus on providing accurate information on the LT4 new formulation, emphasizing efficacy, safety, and bioequivalence with clear guidance and ensure that patients and clinicians are fully informed about any changes to medications such as LT4 to reduce the risk of unrelated adverse events being incorrectly attributed to the newer formulation.

Case report: A rare case of thyrotropin-secreting pituitary macroadenoma with diffuse calcification presenting with hyperthyroidism and literature review

Background

Thyroid-stimulating hormone (TSH)-secreting pituitary adenomas (TSHomas) are rare and usually present with hyperthyroidism. Calcification in pituitary tumors is an infrequent finding. Herein, we report an extremely rare case of TSHoma with diffuse calcification.

Case description

A 43-year-old man was admitted to our department with a complaint of palpitations. An endocrinological examination revealed elevated serum levels of TSH, free triiodothyronine (FT3), and free thyroxin, whereas the physical examination revealed no obvious abnormality. Computerized tomography (CT) showed a sellar mass with diffuse calcification. Contrast-enhanced T1-weighted images revealed a less-enhancing tumor without obvious suprasellar or parasellar expansion. The tumor was completely removed via endoscopic transnasal-sphenoidal surgery. Microscopically, nests of cells were inconspicuous among the diffuse psammoma bodies. Expression of TSH was patchy, and only several TSH-positive cells were observed. Postoperatively, the serum levels of TSH, FT3, and FT4 decreased to their normal range. Follow-up MR images showed no evidence of residual tumor or regrowth after the resection.

Conclusions

Herein, we report a rare case of TSHoma with diffuse calcification that presented with hyperthyroidism. A correct and early diagnosis was made according to the European Thyroid Association guidelines. This tumor was completely removed via endoscopic transnasal-transsphenoidal surgery (eTSS), and thyroid function was normalized after the operation.

Getting the levothyroxine (LT4) dose right for adults with hypothyroidism: opportunities and challenges in the use of modern LT4 preparations

Lifelong treatment with levothyroxine (LT4) is the mainstay of management for individuals with hypothyroidism. Many hypothyroid patients start LT4 treatment at a low dose (e.g. 25-50 µg), especially the elderly, those with residual thyroid function, those with low body weight, and those with significant (especially cardiac) comorbidities. Almost half of patients on LT4 replacement therapy demonstrate either under- or over-treatment. Many LT4 preparations have relatively large intervals between tablet strengths at the lower end of their dose ranges (providing 25 µg, 50 µg, and 75 µg tablets), which may represent a barrier to achieving the optimum maintenance treatment for some patients. The availability of intermediate tablet strengths of LT4 in the 25-75 µg range may facilitate precise and effective dose titration of LT4 and may also enable convenient maintenance regimens based on a single LT4 tablet daily, to support adherence to therapy.

A Proposed Approach for the Determination of the Bioequivalence Acceptance Range for Narrow Therapeutic Index Drugs in the European Union

The current regulatory criterion for bioequivalence of narrow therapeutic index (NTI) drugs in the European Union requires that the 90% confidence interval for the ratio of the population geometric means of the test product compared with the reference for area under the plasma concentration-time curve (AUC), and in certain cases maximum plasma drug concentration (C_max ), to be included within the tighter acceptance range of 90.00-111.11%. As a consequence, sponsors need to recruit a higher number of subjects to demonstrate bioequivalence and this may be seen as increasing the burden for the development of generics. This "one-size-fits-all" criterion is particularly questionable when the within-subject variability of the reference product is moderate to high. As an alternative, we propose a further refined statistical approach where the acceptance range is narrowed based on the within-subject variability of the reference product of the NTI drug, similar to the one used for widening the standard 80.00-125.00% acceptance range for highly variable drugs. The 80.00-125.00% acceptance range is narrowed, only if the within-subject variability is lower than 30%, down to the current NTI acceptance range of 90.00-111.11% when the within-subject variability is 13.93% or lower. Examples within the current European Medicines Agency list of NTI drugs show a considerable reduction in required sample size for drugs like tacrolimus and colchicine, where the predicted within-subject variability is 20-30%. In these cases, this approach is less sample size demanding without any expected increase in the therapeutic risks, since patients treated with reference products with moderate to high within-subject variability are frequently exposed to bioavailability differences larger than 10%.

The Role of Thyroid Function in Alzheimer's Disease

The thyroid gland is crucial for the regulation of metabolism, growth, and development of various tissues, organs, systems, including the central nervous system. Recent studies have implicated the role of thyroid dysfunction in the etiology of Alzheimer's disease (AD), while AD leads to a significant increase in the prevalence of thyroid dysfunction. In this review, we have analyzed the role of thyroid function in the pathophysiology of AD as well as its biomarkers. The present review aims to provide encouraging targets for early screening of AD risk factors and intervention strategies.

Treatment of subclinical hypothyroidism: assessing when treatment is likely to be beneficial

Introduction: Subclinical hypothyroidism (SCH) is a common condition diagnosed in up to 16% of the population. SCH is diagnosed when serum TSH is high and circulating thyroid hormones are within the reference range. SCH is considered to be a mild form of thyroid failure by some due to the log-linear relationship between TSH and thyroid hormones. Nevertheless, it is unclear whether the treatment of SCH with thyroid hormones is beneficial, and hence, it is not surprising that expert opinions and recommendations from societies differ in their opinions on how best to manage SCH.Areas covered: This article reviews the currently available evidence pertaining to SCH and provides recommendations as to when treatment of SCH should be considered. An electronic search of PubMed from 1970 to 2019 was performed and systematically reviewed studies assessing the effects of treatment in SCH. The main areas that are considered are the effects of treatment on symptoms and quality of life, and important clinical consequences including psychocognitive outcomes and cardiovascular events.Expert opinion: Treatment of SCH with thyroid hormones is debated and the current literature in this area lacks clarity. We provide an evidence-based recommendation for when treatment of SCH with thyroid hormones should be considered.

Managing symptoms in hypothyroid patients on adequate levothyroxine: a narrative review

The current standard of care for hypothyroidism is levothyroxine (LT4) monotherapy to reduce levels of thyrotropin (thyroid-stimulating hormone, TSH) within its reference range and amelioration of any symptoms. A substantial minority continues to report hypothyroid-like symptoms despite optimized TSH, however. These symptoms are not specific to thyroid dysfunction and are frequent among the euthyroid population, creating a therapeutic dilemma for the treating clinician as well as the patient. We present a concise, narrative review of the clinical research and evidence-based guidance on the management of this challenging population. The clinician may endeavor to ensure that the serum TSH is within the target range. However, the symptomatic patient may turn to alternative non-evidence-based therapies in the hope of obtaining relief. Accordingly, it is important for the clinician to check for conditions unrelated to the thyroid that could account for the ongoing symptoms such as other autoimmune conditions, anemia or mental health disorders. Systematic and thorough investigation of the potential causes of persistent symptoms while receiving LT4 therapy will resolve the problem for most patients. There may be some patients that may benefit from additional treatment with liothyronine (LT3), although it is unclear as yet as to which patient group may benefit the most from combined LT4 + LT3 therapy. In the future, personalized treatment with LT4 + LT3 may be of benefit for some patients with persistent symptoms of hypothyroidism such as those with polymorphisms in the deiodinase enzyme 2 (DIO2). For now, this remains a subject for research.

Artificial intelligence may offer insight into factors determining individual TSH level

The factors that determine Serum Thyrotropin (TSH) levels have been examined through different methods, using different covariates. However, the use of machine learning methods has so far not been studied in population databases like NHANES (National Health and Nutritional Examination Survey) to predict TSH. In this study, we performed a comparative analysis of different machine learning methods like Linear regression, Random forest, Support vector machine, multilayer perceptron and stacking regression to predict TSH and classify individuals with normal, low and high TSH levels. We considered Free T4, Anti-TPO antibodies, T3, Body Mass Index (BMI), Age and Ethnicity as the predictor variables. A total of 9818 subjects were included in this comparative analysis. We used coefficient of determination (r²) value to compare the results for predicting the TSH and show that the Random Forest, Gradient Boosting and Stacking Regression perform equally well in predicting TSH and achieve the highest r² value = 0.13, with mean absolute error of 0.78. Moreover, we found that Anti-TPO is the most important feature in predicting TSH followed by Age, BMI, T3 and Free-T4 for the regression analysis. While classifying TSH into normal, high or low levels, our comparative analysis also shows that Random forest performs the best in the classification study, performed with individuals with normal, high and low levels of TSH. We found the following Areas Under Curve (AUC); for low TSH, AUC = 0.61, normal TSH, AUC = 0.61 and elevated TSH AUC = 0.69. Additionally, we found that Anti-TPO was the most important feature in classifying TSH. In this study, we suggest that artificial intelligence and machine learning methods might offer an insight into the complex hypothalamic-pituitary -thyroid axis and may be an invaluable tool that guides us in making appropriate therapeutic decisions (thyroid hormone dosing) for the individual patient.

Need for Completion Thyroidectomy in Patients Undergoing Lobectomy for Indeterminate and High-Risk Nodules: Impact of Intra-Operative Findings and Final Pathology

INTRODUCTION

Current guidelines increasingly suggest the use of thyroid lobectomy for indeterminate (Bethesda 3 and 4) and high-risk (Bethesda 5 and 6) thyroid nodules; however, the clinical reality is often very different.

MATERIALS AND METHODS

The aim of this study was to determine the rate of completion thyroidectomy (CTx) for indeterminate and high-risk thyroid nodules which are pre-operatively classified as suitable for unilateral resection (lobe eligible) based on current guidelines. Seven hundred consecutive patients with thyroid nodules and FNA cytology over four years (2015-2018) were reviewed.

RESULTS

Distribution of the dominant nodules by Bethesda was: non-diagnostic 3.9%, benign 28.1%, atypia of unknown significance 19.0%, follicular neoplasm 23.6%, suspicious for malignancy 6.1% and malignancy 19.3%. Of 298 indeterminate nodules, 68.8% (205/298) had relative but independent indications for a total thyroidectomy (TTx) and the remainder were candidates for lobectomy. For these lobe eligible patients, the overall risk of ultimately needing a TTx was 19.4% (18/93), comprising 4.3% (4/93) from intra-operative findings and 15.7% (14/89) from final pathology. Similarly, of 170 high-risk nodules, 63.5% (108/170) had upfront indications for a TTx and the remaining 62 nodules were lobe eligible. Of the patients taken to the operating room for a lobectomy, 21.0% (13/62) were upgraded to a TTx intra-operatively and 26.5% (13/49) post-operatively. The lobe success rate for indeterminate nodules was 25.2% and for high-risk nodules was 21.2%. The rate of CTx, or the proportion of patients needing a second operation was 15.7% (14/89) and 26.5% (13/49), respectively.

CONCLUSIONS

In counselling a patient for surgery, the risk of needing a more radical initial procedure or second surgery needs to be accurately explained. There are three points of care that can influence operative strategy, pre-operatively by way of high-risk clinical factors, intra-operatively via anatomical findings and post-operatively in response to unrecognized pathological features. Additionally, the patient's personal value judgment and level of risk aversion should be taken into consideration.