TSH Normalization in Bariatric Surgery Patients After the Switch from L-Thyroxine in Tablet to an Oral Liquid Formulation

[Bariatric surgery and drugs: Review of the literature and Adverse Drug Reactions analysis in French National Pharmacovigilance Database]

INTRODUCTION

Bariatric surgery is the only treatment for severe obesity (BMI>35kg/m2) currently recognized as effective both in achieving tangible and lasting weight loss, and in improving obesity-related comorbidities such as type 2 diabetes, hypertension, and cardiovascular complications. Bariatric surgery, like any other surgery of the digestive tract, can have an impact on nutrient absorption, as well as on drug absorption. The literature on drug management in bariatric surgery patients concerned mainly of case reports and retrospective studies involving a small number of patients. No official guidelines are available.

METHODS

We conducted a literature search on the consequences of bariatric surgery in terms of drug bioavailability and/or effect. The Medline® (PubMed) database was searched using the following keywords: "bariatric surgery", "bioavailability", "gastric bypass", and "obesity". We completed this review with an analysis of reports of adverse drug reactions (ADRs) in post-bariatric surgery patients for obesity registered in the National pharmacovigilance database (PVDB). We selected all cases with the mention of "bariatric surgery and/or gastrectomy" as "medical history". After reading the cases, we excluded those in which the patient had undergone surgery for an indication other than obesity, where the route of administration was other than oral, and cases in which ADRs resulted from voluntary overdose, attempted suicide, allergy, switch to Levothyrox® new formulation, meningioma under progestative drugs, inefficacy related to generic substitution and medication error.

RESULTS

The literature search identified mainly "case report" about the impact of bariatric surgery on so-called "narrow therapeutic window" drugs. We identified 66 informative cases out of a total of 565 cases selected (11%) in the PVDB. Nevertheless, the information does not allow a clear relationship between the occurrence of the ADR and the influence of bariatric surgery.

CONCLUSION

There is a lack of official information and/or recommendations on medication use in subjects who have undergone bariatric surgery. Apart from under-reporting, ADRs reports remain largely uninformative. Health professional and patients would be awareness for improving, quantitatively and qualitatively the reporting of ADRs in this population.

Therapeutic efficacy and patient compliance of levothyroxine liquid and softgel formulations taken with meals: a systematic review

PURPOSE

Levothyroxine (L-T4) is the drug of choice for treating primary hypothyroidism. L-T4 tablets should be taken at least 30 min before breakfast. Several studies have suggested that serum thyroid profile is not affected by concomitant intake of liquid/softgel L-T4 with meals. Our aim is to review the evidence on therapeutic efficacy and patient compliance with the liquid and softgel formulation of L-T4 taken with meals, also compared with the standard tablet therapy regimen, in hypothyroid patients.

METHODS

We performed a systematic review of literature by searching PubMed, Embase, and Cochrane Library databases. PRISMA guidelines were applied, and the risk of bias of the included studies was assessed using the RoB 2 and ROBINS tools. The methodological quality was assessed following the GRADE criteria.

RESULTS

We included 13 studies, accounting for a total of 1697 patients. The timing of liquid L-T4 intake from breakfast did not affect the therapeutic efficacy of the treatment. No significant differences in the absorption of liquid L-T4 were found when administered together with different foods, beverages, drugs, or other supplements. TSH levels are not influenced by taking softgel L-T4 at breakfast; the efficacy of softgel and liquid formulation is similar when they are taken with a meal, but superior to that of tablet formulation. Shifting from L-T4 tablets taken 30 min before breakfast to liquid/softgel formulation taken with the meal improved medication adherence and perceived quality of life of patients.

CONCLUSION

Liquid and softgel formulation of L-T4 can be taken at breakfast or close to meals, without losing therapeutic efficacy. These formulations could also improve patient compliance and quality of life compared to L-T4 tablet therapy taken 30 min before breakfast.

Hypothyroidism and metabolic cardiovascular disease

Cardiovascular disease (CVD) remains the leading cause of death worldwide, representing a major health issue of social and economic relevance. Both hyperthyroidism and hypothyroidism are very common in the adult population, and both disorders may contribute to the onset and progression of CVD. After a brief description of the role of thyroid hormones (THs) on the physiology of the cardiovascular system and the potential mechanism that links THs alterations with changes in cardiac function, blood pressure, endothelial function, and lipid levels, we review updated data about the clinical impact of overt hypothyroidism (OH) and subclinical hypothyroidism (SCH) on CV risk, CVD, and mortality. Furthermore, we summarize the current evidence for treating SCH with levothyroxine (L-T4). Several guidelines of distinguished endocrine societies recommend treatment for SCH with TSH higher than 10 mIU/L, where the benefit of L-T4 therapy is more evident for younger people, but still controversial in those aged over 65 years. Based on current knowledge, more research efforts are needed to better address the clinical management of CV risk and CVD in the elderly affected by SCH.

Obesity and Obesity-Related Thyroid Dysfunction: Any Potential Role for the Very Low-Calorie Ketogenic Diet (VLCKD)?

PURPOSE OF REVIEW

This review aims to explore in-depth the different aspects of the association between very low-calorie ketogenic diet (VLCKD), obesity and obesity-related thyroid dysfunction.

RECENT FINDINGS

The VLCKD, proposed as a non-pharmacological strategy for the management of certain chronic diseases, is becoming increasingly popular worldwide. Initially used to treat epilepsy, it has been shown to be effective in controlling body weight gain and addressing various pathophysiological conditions. Research has shown that a low-calorie, high-fat diet can affect thyroid hormone levels. Weight loss can also influence thyroid hormone levels. Studies have suggested that long-term use of VLCKD for refractory epilepsy may be related to the development of hypothyroidism, with an effect seen in various populations. In particular, women with obesity following VLCKD tend to have reduced T3 levels. We propose further research to unravel the underlying mechanisms linking VLCKD to obesity and obesity-related thyroid dysfunction.

Lactose intolerance and levothyroxine malabsorption: a review of the literature and report of a series of patients treated with liquid L-T4 without lactose

In hypothyroid patients needing large doses of levothyroxine (L-T4) (>1.7-2 μg/kg/day) to reach euthyroidism, lactose intolerance (LI) needs to be excluded, owing to the high prevalence in the population. If LI is present, a lactose-free diet decreases the rate of L-T4 malabsorption. However, an increased requirement of L-T4 is described in patients with LI, which can be beneficially treated using lactose-free L-T4 formulation. The lactose-free liquid L-T4 formulation is able to circumvent LI malabsorption leading to the normalization of thyroid-stimulating hormone (TSH) in patients with subclinical hypothyroidism and long-term stable TSH levels.

Myxedema coma secondary to levothyroxine malabsorption in a patient previously submitted to bariatric surgery

Treating hypothyroidism can be challenging in patients with malabsorption, as they require a higher daily dose of oral levothyroxine (L-T4). Oral L-T4 absorption occurs mainly in the jejunum and the ileum and is affected by gastric acidity. As a result, absorption can be impaired by bariatric surgery. This paper presents a case of myxedema in a young man who had previously undergone biliopancreatic diversion. He was referred to the Emergency Department with deteriorated mental state, hypotension, bradycardia and hypothermia. Laboratory tests revealed severe hypothyroidism and hypokalaemia. The clinical and biochemical profile of the patient suggested myxedema coma. The tablet-based L-T4 therapy was replaced with intravenous (iv) L-T4, oral liquid L-T4 and oral liothyronine (L-T3) and inotropic agents and supportive care were also administered, resulting in a gradual improvement in clinical condition. The patient reported taking L-T4 tablets as prescribed before hospitalization. In patients with malabsorption, impaired L-T4 absorption may lead to severe forms of hypothyroidism. This case outlines the need for more frequent monitoring of serum Thyroid Stimulating Hormone in patients submitted to bariatric surgery and suggests the benefit of using liquid L-T4 in the place of tablets in cases of malabsorption.

Levothyroxine personalized treatment: is it still a dream?

Levothyroxine is a milestone in the treatment of all causes of hypothyroidism. From 19th century till today, Levothyroxine experienced a great advancement, from hypodermic injections of an extract of the thyroid gland of a sheep to novel formulations, known to circumvent malabsorption issue. However, the rate of patients on suboptimal therapy is still high. Current Guidelines are clear, daily Levothyroxine dosage should be calculated based on body weight. However, we are still far away from the possibility to administer the right dosage to the right patient, for several reasons. We retrace the history of treatment with levothyroxine, pointing out strengths and weaknesses of different formulations, with particular attention to what keeps us away from tailored therapy. In the age of digitalization, the pharmaceutical industry has been giving rising importance to Digital therapeutics, that are known to be effective in reaching target therapies. By combining current knowledge of hypothyroidism therapy with cutting-edge technology, we also hypothesized what could be the future strategies to be developed in this field.

Insight of the Biopharmaceutical Implication of Sleeve Gastrectomy on Levothyroxine Absorption in Hypothyroidism Patients

PURPOSE

The growing rate of obesity led to an increased number of bariatric surgeries (BS) as a treatment option for obesity. The gastrointestinal tract (GIT) changes following BS can impact many drugs' absorption. Levothyroxine (LT4) is a synthetic thyroxine (T4) replacement used commonly as tablets to manage hypothyroidism disorder, which is more prevalent among patients with obesity. This study aims to examine the LT4 oral tablet form therapy after sleeve gastrectomy.

MATERIALS AND METHODS

A retrospective cohort study was conducted in multi-center. The LT4 doses and TSH and T4 levels were compared before and after BS. The post-surgery readings were categorized into three periods: (one to three months), (four to six months), and (> six ) months after surgery. ANOVA test was used for analysis.

RESULTS

A total of 14374 patients who underwent BS from (1/2019 to 3/2022) were screened for eligibility, and n = 101 participants matched the inclusion criteria. The TSH and T4 were not statistically significant differences before and after surgery (P-values of 0.4864 and 0.5970, respectively). However, the doses significantly differed before and after surgery in all the follow-up time point periods (P < 0.002).

CONCLUSION

The LT4 required doses significantly reduced after sleeve gastrectomy, which can be related to the improved endogenous thyroid production in patients with obesity. However, the abnormality of the GIT induced by the sleeve gastrectomy may affect the exogenous LT4 absorption. Using liquid forms of LT4 while monitoring the thyroid function parameters can optimize the treatment after the procedure.

Subclinical Hypothyroidism in Patients with Obesity and Metabolic Syndrome: A Narrative Review

The literature on the connection between obesity, metabolic syndrome, and subclinical hypothyroidism is critically analyzed in this narrative review. These conditions are frequently observed among adult populations and various studies and meta-analyses have assessed their association. The prevalence of subclinical hypothyroidism in obese individuals is higher than in non-obese subjects and this trend is more pronounced in unhealthy obesity phenotypes. However, the diagnosis and treatment of subclinical hypothyroidism can be difficult in obese patients. Exaggerated body fat is linked to thyroid hypoechogenicity as evident through ultrasonography and euthyroid obese people have greater TSH, FT3, and FT3/FT4 ratios than non-obese individuals in a euthyroid condition. Moreover, a reduced expression of the TSH receptor and altered function of deiodinases has been found in the adipose tissue of obese patients. Current data do not support the necessity of a pharmacological correction of the isolated hyperthyrotropinemia in euthyroid obese patients because treatment with thyroid hormone does not significantly improve weight loss and the increase in serum TSH can be reversible after hypocaloric diet or bariatric surgery. On the other hand, obesity is linked to elevated leptin levels. Inflammation can raise the risk of Hashimoto thyroiditis, which increases the likelihood that obese patients will experience overt or subclinical hypothyroidism. Both metabolic syndrome and subclinical hypothyroidism are associated with atherosclerosis, liver and kidney disease. Hence, the association of these two illnesses may potentiate the adverse effects noted in each of them. Subclinical hypothyroidism should be identified in patients with obesity and treated with appropriate doses of L-thyroxine according to the lean body mass and body weight. Randomized controlled trials are necessary to verify whether treatment of thyroid deficiency could counteract the expected risks.

Interference or Noninterference Between Soy and Levothyroxine: That Is the Question. A Narrative Review of Literature

OBJECTIVE

To evaluate the effect of soy intake on levothyroxine (L-T4) absorption among different L-T4 formulations.

METHODS

A PubMed/MEDLINE, Web of Science, and Scopus research was performed. Case reports, case series, and original studies written in English and published online up to November 30, 2022, were selected and reviewed. The final reference list was defined based on the relevance of each study to the scope of this review.

RESULTS

Few data, mainly case reports, seemed to suggest a possible interference of soy products on L-T4 tablets absorption. However, the only prospective randomized cross-over study showed no differences in L-T4 absorption when L-T4 and soy isoflavones were assumed concomitantly. The very little data available on liquid L-T4 formulations did not allow for any conclusions to be made, even if a double-blind placebo-controlled trial showed no impaired L-T4 absorption.

CONCLUSION

The inference of soy products on L-T4 absorption, if present, seems to have little clinical impact. Considering this fact, the Hamlet-like question whether soy milk interferes with L-T4 absorption remains unanswered.

Efficacy and safety of postoperative levothyroxine sodium tablets for improving serum thyroid hormone levels and tumor marker levels in patients with thyroid tumors

Levothyroxine tablet has been used for improving serum thyroid hormones. Despite its efficacy, there has been a persistent recurrence. We aimed to evaluate the efficacy of levothyroxine regimen (administered as sodium tablets or liquid) therapy, including the regime in combination with other thyroxine hormones, to determine its effectiveness and safety regarding thyroid tumor patient outcomes. An electronic search of the online databases (PubMed, EMBASE, and Web of Science) was performed in duplicate independently by two authors (SSK and LPY) to identify any potential studies published in the English language from January 2002 to October 2022. The records were retrieved using keywords and MeSH terms. The Cochrane risk of bias tool in the Review Manager (RevMan software version 5.4.) was used to evaluate the risk of bias in the included studies.  A total of 18 quality studies were reported on levothyroxine tablets. Results showed that liquid levothyroxine was more efficient than tablet levothyroxine. Further results showed that levothyroxine in combination with L-T3 or I-131 was more effective than L-T4 tablet monotherapy for improving thyroid cancer hormones. Levothyroxine tablet monotherapy is less efficient than liquid levothyroxine and/or levothyroxine combined therapy. This research recommends future research using larger randomized controlled studies.

Comparative Bioavailability of a Novel Solution and a Tablet Formulation of Levothyroxine

Levothyroxine (LT4) is the standard of care for treating hypothyroidism. Despite the established efficacy of LT4, 50% of treated patients fail to achieve normal thyrotropin levels. Oral formulations of LT4 that bypass the gastric phase of dissolution may offset some of the therapeutic shortcomings observed with tablets. An oral solution of LT4 can be administered to patients who are unable to swallow tablets; allows flexibility to individualize dosing; and may mitigate interference with LT4 absorption caused by food, coffee, increased gastric pH from atrophic gastritis, and malabsorption from bariatric surgery. The bioavailability of a novel LT4 oral solution and a reference LT4 tablet were compared in a randomized, laboratory-blinded, single-dose, 2-period, 2-sequence, crossover study in healthy euthyroid subjects. A single 600-μg oral dose of LT4 solution (30 mL × 100 μg/5 mL) or tablet (2 × 300-μg tablet) was administered under fasting conditions in each study period, and total thyroxine concentrations were measured for 72 hours after administration. The ratio of geometric least-squares means and 90% confidence intervals for area under the concentration-time curve from time 0 to 72 hours and maximum plasma concentration were calculated. Among 42 subjects in the pharmacokinetic population, the geometric least-squares mean ratio of area under the concentration-time curve from time 0 to 72 hours and maximum plasma concentration for baseline-adjusted thyroxine was 109.1% and 107.9%, respectively, meeting Food and Drug Administration bioequivalence criteria. Adverse events (AEs) were similar between treatment groups with no serious AEs or discontinuations for AEs. Comparable bioavailability was observed between the LT4 oral solution and reference tablet after a single oral 600-μg dose under fasting conditions.

The performance of levothyroxine tablet is impaired by bariatric surgery

OBJECTIVE

The aim was to evaluate if bariatric surgery can affect the LT4 performance. The endpoints were the following: 1) difference between LT4 daily dose before and 1 year after surgery, 2) difference between LT4 dose per weight before and 1 year after surgery, 3) difference among LT4 preparations.

METHODS

The study period was between January 2018 and May 2022. Inclusion criteria were a) adults undergone bariatric surgery, b) with proven autoimmune hypothyroidism, c) on LT4 therapy before bariatric surgery, d) using any commercialized LT4 preparation. Excluded were patients a) proven to have or suspected for pre-surgical intestinal malabsorption, b) with other potential interfering factors on LT4 absorption; c) with heart, renal, and/or hepatic failure, d) with recent/current infection/inflammation, e) in pregnancy, f) with incomplete data about LT4 therapy.

RESULTS

According to the selection criteria, 40 patients were included. Both TSH and LT4 daily doses were not significantly different with respect to baseline values. On the contrary, the LT4 dose per weight was significantly increased, especially in RYGB patients. An increased LT4 dose per weight was observed with the reduction of weight.

CONCLUSION

One year after bariatric surgery 1) the daily dose of LT4 remains unchanged, and 2) despite the significant weight reduction, LT4 dose per weight increases. Most data are referred to LT4 tablet and the performance of LT4 caps should be further investigated.

Levothyroxine: Conventional and novel drug delivery formulations

Despite the fact that levothyroxine is one of the most prescribed medications in the world, its bioavailability has been reported to be impaired by many factors, including interfering drugs or foods and concomitant diseases, and persistent hypothyroidism with a high dose of levothyroxine is thus elicited. Persistent hypothyroidism can also be induced by noninterchangeability between formulations and poor compliance. To address these issues, some strategies have been developed. Novel formulations (liquid solutions and soft-gel capsules) have been designed to eliminate malabsorption. Some other delivery routes (injections, suppositories, sprays, and sublingual and transdermal administrations) are aimed at circumventing different difficulties in dosing, such as thyroid emergencies and dysphagia. Moreover, nanomaterials have been used to develop delivery systems for the sustained release of levothyroxine to improve patient compliance and reduce costs. Some delivery systems encapsulating nanoparticles show promising release profiles. In this review, we first summarize the medical conditions that interfere with the bioavailability of oral levothyroxine and discuss the underlying mechanisms and treatments. The efficacy of liquid solutions and soft-gel capsules are systematically evaluated. We further summarize the novel delivery routes for levothyroxine and their possible applications. Nanomaterials in the levothyroxine field are then discussed and compared based on their load and release profile. We hope the article provides novel insights into the drug delivery of levothyroxine.

Levothyroxine-induced serum free thyroxine response following radioactive iodine administration in patients thyroidectomized for differentiated thyroid cancer: A randomized controlled trial

PURPOSE

Patients undergoing thyroidectomy for differentiated thyroid cancer (DTC) may require 131-radioactive iodine (RAI) administration for remnant ablation or disease treatment. After ingestion, RAI resides within the gastrointestinal tract potentially leading to mucosal damage and abnormalities in the absorption of levothyroxine (LT4). The aim of this study was to evaluate whether serum FT4 peak, induced by a LT4 challenge, changes according to the LT4 formulation (solid or liquid) in both RAI and non-RAI-treated DTC patients.

METHODS

This was a monocentric controlled clinical trial, with a parallel two-groups (1:1) randomization of sequence of LT4 formulation. Patients received 200 mcg LT4 orally administered at 08:00 h, in both solid and liquid formulation, at one-week interval, at baseline and after 1, 3, and 6 months from RAI administration. At each time-point, circulating FT4 was evaluated both before LT4 assumption as well as after 1 and 3 h. FT4 increments were evaluated as area under the curve response (AUC). Analogous protocol with the same time-intervals was followed for non-RAI patients.

RESULTS

The trial included 29 consecutive DTC patients, nineteen of whom were submitted to RAI. In RAI subjects, we observed an overall significant reduction in serum FT4 increments with the most relevant decrease at the 1-month time-point, (FT4 AUC: 4.46 ± 0.72 (M ± SD) vs 4.07 ± 0.63 in baseline vs 1-month, P = 0.001) without any difference between the two LT4 formulations. No difference in serum FT4 AUC was found in non-RAI subjects.

CONCLUSION

LT4-induced serum FT4 responses are reduced following RAI administration in thyroidectomized DTC patients.

Antiallergic Treatment of Bariatric Patients: Potentially Hampered Solubility/Dissolution and Bioavailability of Loratadine, but Not Desloratadine, Post-Bariatric Surgery

Gastrointestinal anatomical/physiological changes after bariatric surgery influence variables affecting the fate of drugs after ingestion, and medication management of these patients requires a thorough and complex mechanistic analysis. The aim of this research was to study whether loratadine/desloratadine antiallergic treatment of bariatric patients is at risk of being ineffective due to impaired solubility/dissolution. The pH-dependent solubility of loratadine/desloratadine was studied in vitro, as well as ex vivo, in gastric content aspirated from patients before versus after bariatric surgery. Then, a biorelevant dissolution method was developed to simulate the gastric conditions after sleeve gastrectomy (SG) or one-anastomosis gastric bypass (OAGB), accounting for key variables (intragastric volume, pH, and contractility), and the dissolution of loratadine/desloratadine was studied pre- versus post-surgery. Dissolution was also studied after tablet crushing or syrup ingestion, as these actions are recommended after bariatric surgery. Finally, these experimental data were implemented in a newly developed physiologically based pharmacokinetic (PBPK) model to simulate loratadine/desloratadine PK profiles pre- versus post-surgery. For both drugs, pH-dependent solubility was demonstrated, with decreased solubility at higher pH; over the pH range 1-7, loratadine solubility decreased ∼2000-fold, and desloratadine decreased ∼120-fold. Ex vivo solubility in aspirated human gastric fluid pre- versus post-surgery was in good agreement with these in vitro results and revealed that while desloratadine solubility still allows complete dissolution post-surgery, loratadine solubility post-surgery is much lower than the threshold required for the complete dissolution of the drug dose. Indeed, severely hampered loratadine dissolution was revealed, dropping from 100% pre-surgery to only 3 and 1% post-SG and post-OAGB, respectively. Tablet crushing did not increase loratadine dissolution in any post-bariatric condition, nor did loratadine syrup in post-OAGB (pH 7) media, while in post-laparoscopic SG conditions (pH 5), the syrup provided partial improvement of up to 40% dissolution. Desloratadine exhibited quick and complete dissolution across all pre-/post-surgery conditions. PBPK simulations revealed pronounced impaired absorption of loratadine post-surgery, with 84-88% decreased C_max, 28-36% decreased F_a, and 24-31% decreased overall bioavailability, depending on the type of bariatric procedure. Desloratadine absorption remained unchanged post-surgery. We propose that desloratadine should be preferred over loratadine in bariatric patients, and as loratadine is an over-the-counter medication, antiallergic therapy after bariatric surgery requires special attention by patients and clinicians alike. This mechanistic approach that reveals potential post-surgery complexity, and at the same time provides adequate substitutions, may contribute to better pharmacotherapy and overall patient care after bariatric surgery.

Factors influencing the levothyroxine dose in the hormone replacement therapy of primary hypothyroidism in adults

Levothyroxine (LT4) is a safe, effective means of hormone replacement therapy for hypothyroidism. Here, we review the pharmaceutical, pathophysiological and behavioural factors influencing the absorption, distribution, metabolism and excretion of LT4. Any factor that alters the state of the epithelium in the stomach or small intestine will reduce and/or slow absorption of LT4; these include ulcerative colitis, coeliac disease, bariatric surgery, Helicobacter pylori infection, food intolerance, gastritis, mineral supplements, dietary fibre, resins, and various drugs. Once in the circulation, LT4 is almost fully bound to plasma proteins. Although free T4 (FT4) and liothyronine concentrations are extensively buffered, it is possible that drug- or disorder-induced changes in plasma proteins levels can modify free hormone levels. The data on the clinical significance of genetic variants in deiodinase genes are contradictory, and wide-scale genotyping of hypothyroid patients is not currently justified. We developed a decision tree for the physician faced with an abnormally high thyroid-stimulating hormone (TSH) level in a patient reporting adequate compliance with the recommended LT4 dose. The physician should review medications, the medical history and the serum FT4 level and check for acute adrenal insufficiency, heterophilic anti-TSH antibodies, antibodies against gastric and intestinal components (gastric parietal cells, endomysium, and tissue transglutaminase 2), and Helicobacter pylori infection. The next step is an LT4 pharmacodynamic absorption test; poor LT4 absorption should prompt a consultation with a gastroenterologist and (depending on the findings) an increase in the LT4 dose level. An in-depth etiological investigation can reveal visceral disorders and, especially, digestive tract disorders.

Thyroid Function Alteration in Obesity and the Effect of Bariatric Surgery

The most common endocrine disease in obesity is hypothyroidism and secondary endocrine alterations, including abnormal thyroid function, are frequent in obesity. It is unclear whether impaired thyroid function is the cause or the consequence of increased adiposity; furthermore, there are no clear data regarding the best way to dose levothyroxine for patients with both hypothyroidism and obesity, and the effect of bariatric surgery (BS). The aim of the present article is to review some controversial aspects of the relation between obesity and the thyroid: (1) Thyroid function in obesity and the effect of BS (2) Thyroid hormone treatment (THT) in obese patients with hypothyroidism and the effect of BS. In summary: In morbidly obese patients, TSH is moderately increased. Morbid obesity has a mild central resistance to the thyroid hormone, reversible with weight loss. In morbidly obese hypothyroid patients, following weight loss, the levothyroxine dose/kg of ideal weight did not change, albeit there was an increment in the levothyroxine dose/kg of actual weight. From a clinical practice perspective, in morbid obesity, diagnosing mild hypothyroidism is difficult, BS improves the altered thyroid function and THT can be adapted better if it is based on ideal weight.

Liquid levothyroxine formulations in patients taking drugs interfering with L-T4 absorption

PURPOSE

To describe the current knowledge on thyroid hormonal profile in patients on liquid L-T4 therapy and drugs known to interfere with L-T4 absorption.

METHODS

A PubMed/MEDLINE, Web of Science, and Scopus research was performed. Case reports, case series, original studies and reviews written in English and published online up to 31 August 2022 were selected and reviewed. The final reference list was defined based on the relevance of each paper to the scope of this review.

RESULTS

The available data showed that novel levothyroxine formulations circumvent gastric pH impairment due to multiple interfering drugs such as proton pump inhibitors, calcium or iron supplements, sevelamer, aluminum/magnesium hydroxide and sodium alginate.

CONCLUSION

New formulations can be taken simultaneously with drugs interfering with L-T4 absorption, in particular liquid formulations. Softgel capsules need more studies to support these data.

Precision Medicine in Autoimmune Thyroiditis and Hypothyroidism

Autoimmune thyroid diseases (AITD) are T-cell-mediated organ specific autoimmune disorders, deriving from an altered response of the immune system that leads to the immune attack to the thyroid. Hashimoto’s thyroiditis (HT) and Graves’ disease (GD) are the two principal AITD clinical presentations. Hypothyroidism and thyrotoxicosis are, respectively, the clinical hallmarks of HT and GD. Patients with autoimmune thyroiditis are treated daily with synthetic L-thyroxine (L-T4) at the dose of 1.5–1.7 μg/kg. Various L-T4 formulations are commercially available (tablet, liquid solution, or soft gel capsule). L-T4 in tablets is generally prescribed to treat hypothyroidism, whereas the liquid formulation, or soft gel capsules, can be administered in hypothyroid patients in case of malabsorption or in patients in therapy with drugs interfering with L-T4 absorption. Furthermore, myoinositol has a crucial role in thyroid autoimmunity and function. Clinical studies reported a significant decline in TSH and antithyroid autoantibodies levels after treatment with myoinositol + selenium in patients with subclinical hypothyroidism and autoimmune thyroiditis. Moreover, thyroidectomy can be rarely recommended in patients with autoimmune thyroiditis, with cosmetic reasons for a goiter, or with important signs or symptoms of local compression, or nodular disease with a “suspicious” cytology for malignancy. Furthermore, a recent randomized trial suggested that total thyroidectomy can improve quality of life and fatigue, while medical therapy did not. In this review, we overview currently available evidence in personalized medicine in patients with autoimmune thyroiditis and hypothyroidism. Further research is needed in larger population to investigate the effect of these new treatments on quality of life.

Improvements in Quality of Life and Thyroid Parameters in Hypothyroid Patients on Ethanol-Free Formula of Liquid Levothyroxine Therapy in Comparison to Tablet LT4 Form: An Observational Study

Levothyroxine (LT4) is a standard therapy in hypothyroidism; however, its bioavailability and therapeutic effects might be affected by many factors. Data shows that therapy with liquid LT4 characterized by quicker pharmacokinetics provides better thyroid hormones control than tablet LT4. We addressed the quality of life (QoL) and efficacy of the new ethanol-free formula of liquid LT4 (Tirosint^®SOL) treatment in 76 euthyroid patients with primary (PH, n = 46) and central hypothyroidism (CH, n = 30), and compared the results to retrospective data on equivalent doses of tablet L-T4 therapy. After 8 weeks of liquid LT4 therapy, we found a significant improvement in QoL in both PH and CH patients. TSH levels were unaltered in PH patients. Free hormone levels (fT4 and fT3) increased in all the patients, with the exception of fT3 in the CH group. SHBG and low-density lipoprotein (LDL) also improved. Liquid LT4 therapy provided a better thyroid hormone profile and improvement in patients' QoL than the tablet form, which was possibly due to the more favorable pharmacokinetics profile resulting in better absorption, as suggested by the increased free thyroid hormone levels. In summary, this is the first study addressing the QoL in hypothyroid patients, including primary and central hypothyroidism, treated with liquid LT4 formula in everyday practice.

Evaluation of Thyroid Hormone Replacement Dosing in Morbidly Obese Hypothyroid Patients after Bariatric Surgery-Induced Weight Loss

The most frequent endocrine disease in obese patients is hypothyroidism. To date, there are no clear data regarding what happens to the dose of levothyroxine (LT4) after bariatric surgery (BS). The objective of the present study was to evaluate thyroid hormone replacement dose in morbidly obese hypothyroid patients after BS-induced weight loss. We explore the best type of measured or estimated body weight for LT4 dosing. We performed an observational study evaluating patients with morbid obesity and hypothyroidism who underwent BS. We included 48 patients (three men). In morbidly obese hypothyroid patients 12 months after BS-induced weight loss, the total LT4 dose or the LT4 dose/kg ideal body weight did not change, while there was a significant increase in LT4 dose/body surface area, LT4 dose/kg weight, LT4 dose/kg adjusted body weight, LT4 dose/kg body fat, and LT4 dose/kg lean body weight. There were no differences in LT4 dose and its variation between sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB). The present study strongly suggests that LT4 dosing in obese hypothyroid patients can be individually adapted more precisely if it is based on ideal body weight.

Effect of Laparoscopic Sleeve Gastrectomy vs. OAGB on Thyroid Function Tests in Patients with Morbid Obesity and Subclinical or Clinical Hypothyroidism

PURPOSE

As one of the major problems for the health sector, morbid obesity is associated with many hormonal dysfunctions, including thyroid hormone disorders. Few studies have been performed on improving subclinical and clinical hypothyroidism following bariatric surgery. Therefore, we designed and conducted this study to evaluate the effect of various types of bariatric surgery on thyroid hormone levels and to assess the change of levothyroxine requirement in these patients.

METHODS

The data of all patients who underwent either sleeve gastrectomy (SG) or one-anastomosis gastric bypass (OAGB) surgery in the 5 years from 2016 to 2020 at our hospital were analyzed retrospectively.

RESULTS

From 1486 patients (792 cases of SG and 694 cases of OAGB), 281 patients had preoperative abnormal thyroid function tests: subclinical hypothyroidism (102 patients) and clinical hypothyroidism (179 patients). The T4 level did not change significantly in any of the groups and subgroups. However, the TSH level at the end of the sixth month after SG and OAGB in both groups significantly lowered. Nevertheless, there is no significant difference between the effect of SG and OAGB surgical procedures on the rate of TSH and T4 alterations in both subclinical and clinical hypothyroid patients. In the sixth month after surgery, 49% of clinically hypothyroid patients in the SG group (n = 179) reduced or stopped taking the medication.

CONCLUSION

Whereas bariatric surgery reduces TSH levels, it does not significantly alter T4 levels. Furthermore, there is no apparent difference between subclinical and clinical hypothyroidism and different types of bariatric surgery.

Oral drug dosing following bariatric surgery: General concepts and specific dosing advice

Bariatric or weight‐loss surgery is a popular option for weight reduction. Depending on the surgical procedure, gastric changes like decreased transit time and volume and increased pH, decreased absorption surface in the small intestine, decreased exposure to bile acids and enterohepatic circulation, and decreased gastrointestinal transit time may be expected. In the years after bariatric surgery, patients will also substantially lose weight. As a result of these changes, the absorption, distribution, metabolism and/or elimination of drugs may be altered. The purpose of this article is to report the general influence of bariatric surgery on oral drug absorption, and to provide guidance for dosing of commonly used drugs in this special population. Upon oral drug administration, the time to maximum concentration is often earlier and this concentration may be higher with less consistent effects on trough concentrations and exposure. Additionally, prescription of liquid formulations to bariatric patients is supported by some reports, even though the high sugar load of these suspensions may be of concern. Studies on extended‐release medications result in an unaltered exposure for a substantial number of drugs. Also, studies evaluating the influence of timing after surgery show dynamic absorption profiles. Although for this group specific advice can be proposed for many drugs, we conclude that there is insufficient evidence for general advice for oral drug therapy after bariatric surgery, implying that a risk assessment on a case‐by‐case basis is required for each drug.

The Effect of Laparoscopic Sleeve Gastrectomy on Serum Thyroid-Stimulating Hormone Levels in Obese Patients with Overt and Subclinical Hypothyroidism: a 7-Year Retrospective Study

BACKGROUND

Inconsistent results were reported by several studies that evaluated the effect of weight loss induced by bariatric surgery on thyroid function panel. This study is aimed at evaluating this effect on thyroid-stimulating hormone (TSH) and thyroid hormone replacement dosages in obese population with overt and subclinical hypothyroidism (SH).

METHODS

A retrospective study was performed on all morbidly obese patients with previous diagnosis of overt and subclinical hypothyroidism who underwent laparoscopic sleeve gastrectomy from October 2009 to January 2017. The correlation between TSH and body mass index (BMI) and the effect of weight loss induced by bariatric surgery on TSH were investigated.

RESULTS

The prevalence of overt and SH in morbidly obese patients was 10.8% and 7.2%, respectively. Thirty-six hypothyroid patients and 67 subclinically hypothyroid patients were included in the study. Hypothyroidism improved in 44.5% of patients and completely resolved in 22.2%, and 33.3% experienced no change. Ninety-one percent of SH patients completely resolved, 6% improved, but 3% worsened, with one patient developed hypothyroidism. Both groups achieved a significant decrease in postoperative BMI. A positively statistically significant association was found between BMI and TSH (p < 0.005).

CONCLUSIONS

Our results favor the effect of laparoscopic sleeve gastrectomy in the obese population with overt and SH as shown by the majority of SH resolution and overt hypothyroidism improvement.

Hypothyroidism and levothyroxine therapy following bariatric surgery: a systematic review, meta-analysis, network meta-analysis, and meta-regression

BACKGROUND

Many health benefits of bariatric surgery are known and well-studied, but there is scarce data on the benefits of bariatric surgery on the thyroid function.

OBJECTIVE

We aimed to make a meta-analysis regarding the impact of bariatric surgery on thyroid-stimulating hormone (TSH) levels, levothyroxine dose, and the status of subclinical hypothyroidism.

SETTING

Systematic review and meta-analysis.

METHODS

PubMed, EMBASE, and Cochrane Library were searched up to December 2020 for relevant clinical studies. Random-effects model was used to pool results. Network meta-analysis was performed, incorporating direct and indirect comparisons among different types of bariatric surgery. Meta-regression analysis was performed to evaluate the impact of moderator variables on TSH levels and required levothyroxine dose after surgery. We followed the PRISMA guidelines for data selection and extraction. PROSPERO registry number: CRD42018105739.

RESULTS

A total of 28 studies involving 1284 patients were included. There was a statistically significant decrease in TSH levels after bariatric surgery (mean difference = -1.66 mU/L, 95%CI [-2.29, -1.03], P < .0001). In meta-regression analysis, we found that the following moderator variables: length of follow-up, mean age, baseline TSH, and preoperative thyroid function, could explain 1%, 43%, 68%, and 88% of the between-study variance, respectively. Furthermore, subclinical hypothyroidism was completely resolved in 87% of patients following bariatric surgery. In addition, there was a statistically significant decrease of levothyroxine dose in frank hypothyroid patients following bariatric surgery (mean difference = -13.20 mcg/d, 95%CI [-19.69, -6.71]). In network meta-analysis, we found that discontinuing or decreasing levothyroxine dose was significant following Roux-en-Y gastric bypass, 1 anastomosis gastric bypass, and sleeve gastrectomy, (OR = 31.02, 95%CI [10.34, 93.08]), (OR = 41.73, 95%CI [2.04, 854.69]), (OR = 104.03, 95%CI [35.79, 302.38]), respectively.

CONCLUSIONS

Based on our meta-analysis, bariatric surgery is associated with the resolution of subclinical hypothyroidism, a decrease in TSH levels, and a decrease in levothyroxine dose.

New Formulations of Levothyroxine in the Treatment of Hypothyroidism: Trick or Treat?

Background: Levothyroxine (LT4) as a medication is used by up to 5.3% of the adult population. For optimal efficacy, the traditional tablet formulation (LT4tab) requires that patients avoid concomitant ingestion with food, drinks, and certain medications, as well as excellent patient compliance. Some comorbidities influence bioavailability of LT4 and may mandate repeated dose adjustments. Summary: New LT4 formulations (soft gel [LT4soft] and liquid [LT4liq]) containing predissolved LT4 are claimed to improve bioavailability, presumably by facilitating absorption. Thus, these formulations may well be more suitable than LT4tab for patients whose daily requirements are subjected to variations in bioavailability. Here, we review the evidence and indications for use of new LT4 formulations and highlight areas of uncertainty that are worthy of further investigation. While bioequivalence is established for LT4soft and LT4liq administered to healthy volunteers compared with LT4tab in pharmacokinetic (PK) studies, therapeutic equivalence of the new formulations seems to be different in several clinical settings. Some evidence suggests that new formulations of LT4 may mitigate against the strict requirements relating to concomitant ingestion with food, drinks, and certain medications, which apply to traditional LT4 tablets. The principal indication is in selected patients with disease fluctuations and intermittent therapies with interfering medications, where the need for frequent dose adjustments and office visits may be diminished. Whether the use of LT4soft or LT4liq in patients with impaired gastric acid secretion results in better control of hypothyroidism than LT4tab remains unclear. Conclusions: The evidence in favor of using LT4soft and LT4liq in clinical practice over LT4tab is weak, and the underlying putative PK mechanisms unclear. Additional studies to investigate these potential benefits, define the cost-effectiveness, and understand the PK mechanisms involved with new LT4 formulations are needed.

The Stability of TSH, and Thyroid Hormones, in Patients Treated With Tablet, or Liquid Levo-Thyroxine

Approximately, 5% of the population is affected by hypothyroidism, mainly women and persons aged more than 60 years. After the diagnosis of hypothyroidism the usual therapy is tablet levothyroxine (L-T4), with a monitoring of the thyroid-stimulating hormone (TSH) level in primary hypothyroidism every 6-8 weeks and L-T4 is adjusted as necessary to reach an euthyroid state. Once TSH is stabilized in the normal range, it is recommended to conduct annual testing in the treated subjects to warrant suitable replacement. More recently advances regarding L-T4 treatment are the introduction of new oral formulations: the liquid solution, and soft gel capsule. The soft gel capsule permits a quick dissolution in the acid gastric pH. The liquid preparation does not require an acid gastric environment. Many pharmacokinetic studies demonstrated a more rapid absorption for the liquid L-T4, or capsule, than with tablet. Many studies have shown that the liquid, or capsule, formulations can overcome the interaction with foods, drugs or malabsorptive conditions, that are able to impair the tablet L-T4 absorption. Lately studies have suggested that liquid L-T4 can permit to maintain more efficiently normal TSH levels in hypothyroid patients in the long-term follow-up, than tablet L-T4, both in patients with malabsorptive states, and in those without malabsorption. Further large, prospective, longitudinal studies are needed to evaluate the stability of TSH, in hypothyroid patients treated with different L-T4 formulations.

L-T4 Therapy in Enteric Malabsorptive Disorders

Levothyroxine (L-T4) absorption can be impaired by various causes: a) L-T4 ingestion during breakfast, or with food; b) conditions of reduced gastric acidity; c) intestinal procedures and diseases such as bariatric surgery, lactose intolerance (LI), celiac disease (CD), inflammatory bowel disease; d) drugs that alter L-T4 absorption, increasing the gastric pH, or preventing the dissolution of tablets. The development of new oral formulations, i.e. the liquid preparation and the soft gel capsule, represents the most recent advance regarding L-T4 therapy. Treating hypothyroidism with L-T4 tablets can lead to an improper control of thyroid-stimulating hormone (TSH) in ~10%-15% of patients. The improperly elevated TSH is usually managed by increasing the L-T4 daily dose, and revaluating TSH upon 2-6 months. The increase of the L-T4 dosage may cause iatrogenic hyperthyroidism, especially when the underlying disorders are cured. Liquid L-T4 can be administered in patients unable to swallow capsules or tablets, and this is one of its major benefits. Liquid L-T4 can: 1- overcome food and beverages interference; 2- bypass the malabsorption associated with an increased gastric pH; 3- circumvent the issue of malabsorption in patients who underwent bariatric surgery; 4-maintain TSH values under control better than L-T4 tablets in hypothyroid patients with typical or atypical CD, or in patients with LI. Few clinical studies evaluated soft gel L-T4 with encouraging findings in patients with gastric- or coffee-related malabsorption, or hypothyroid patients without malabsorption. Additional research is necessary to investigate liquid L-T4, or soft gel capsule, in other conditions of altered L-T4 absorption.

Liquid Levothyroxine Formulation Taken during Lunch in Italy: A Case Report and Review of the Literature

Levothyroxine (L-T4) is among the most widely prescribed medications in the world, and it is considered by the World Health Organization an essential medicine for basic health care. Replacement therapy has always been considered straightforward although different factors may interfere with intestinal absorption of L-T4, including food, dietary fibre, coffee, drugs, and gastrointestinal diseases. For these reasons, current guidelines recommend that L-T4 should be taken in a fasting state because its absorption is maximised when it is taken on an empty stomach, reflecting the importance of gastric acidity in the absorption process. In addition to sodium L-T4 in tablet form, various formulations (soft-gel capsules and liquid solutions) have become available for clinical use in the last years promising improved absorption. We described a 31-year-old Italian man who took liquid levothyroxine formulation during lunch. He was under replacement therapy with liquid levothyroxine 75 mcg daily for hypothyroidism due to Hashimoto thyroiditis for three years. During confirmation of the L-T4 replacement therapy, the patient stated that he was going to continue to “take liquid levothyroxine during (his) lunch every day.” We recommended taking the medication correctly in the morning at least thirty minutes before breakfast and repeating TSH, fT4, and fT3 after three months. The thyroid hormonal profiles taken after 3 and 6 months were comparable to those when the patient was taking the medication during lunch. In conclusion, liquid levothyroxine formulation should be preferred in case of malabsorption or potential malabsorption. Liquid formulation should be preferred due to the possibility of taking it during breakfast, which significantly improves the compliance of patients. Further studies are needed to evaluate the possibility of taking liquid L-T4 during lunch.

Thyroid surgery in obese patients: A review of the literature

The incidence of obesity in the general population has tripled in the past four decades. The number of bariatric surgeries performed annually has quadrupled in the past ten years due to this obesity epidemic. Concomitantly, the number of patients who are obese or who have undergone bariatric surgery and have become candidates for thyroid surgery has also increased considerably. Among patients undergoing thyroidectomy in the French population, the proportion of obese patients currently represents 10 to 20%. In addition, the frequency of benign and malignant thyroid pathologies seems to be increased by obesity, with a Hazard Ratio of around 1.8 for thyroid cancers in obese women. While obesity does not seem to influence the specific post-operative morbidity of thyroidectomy, a history of malabsorptive bariatric surgery should encourage the greatest caution in patients who need to undergo thyroid surgery since it is associated with a significant risk of severe hypocalcemia (>60% in some studies) requiring intravenous calcium supplementation in about 20% of cases. In the latter situation, peri-operative vitamin D-calcium supplementation is essential. In addition, the replacement dose of Levothyroxine (T4) intended for replacement must also be adapted in obese patients, calculated not from the actual weight but from the ideal weight. The objective of this review is to discuss the influence of obesity on the evolution of nodular and neoplastic thyroid pathologies, on the morbidity of thyroid surgery as well as on post-operative drug treatments. The impact of bariatric surgery on these different aspects is also discussed.

Use of Thyroid Hormones in Hypothyroid and Euthyroid Patients; the 2019 Italian Survey

BACKGROUND

The incidence and prevalence of hypothyroidism are increasing and the threshold for the treatment of hypothyroid as well as individuals without evident thyroid disease with thyroid hormone is declining.

OBJECTIVE

To investigate endocrinologists' use of thyroid hormones in hypothyroid and euthyroid patients in Italy, a country where different formulations of levothyroxine (LT4; tablet, liquid solution and soft-gel capsule) are available on the market.

METHODS

Members of the Associazione Medici Endocrinologi (Italian Association of Clinical Endocrinologists) were invited to participate in a web-based survey investigating the topic.

RESULTS

A total of 797 of 2,028 (39.3%) members completed all the sections of the survey; 98.7% declared that the treatment of choice for hypothyroidism is LT4. A significant minority (37.3%) indicated that LT4 may be considered in infertile euthyroid women seeking pregnancy and harbouring positive thyroperoxidase antibodies (TPOAb) and in goitre increasing in size (18.1%). LT4 + LT3 was considered by 43.2% for LT4-replaced patients and normal TSH, if they reported persistent symptoms. High percentages of respondents chose LT4 in a liquid solution or soft-gel capsules when taken together with other drugs interfering with LT4 absorption (81.8%), in patients with a history of celiac disease, malabsorption, lactose intolerance, intolerance to common excipients (96.6%), or unexplained poor biochemical control of hypothyroidism (74.4%), or in patients not able to adhere to ingesting LT4 fasted and/or separated from food/drink (98.9%). In total, 43.6% of responders would use LT4 in a liquid solution or soft-gel capsules for hypothyroid patients with biochemical euthyroidism on LT4, who had persistent symptoms.

CONCLUSIONS

The preferred treatment for hypothyroidism is LT4; LT3 + LT4 combination treatment is mainly considered in patients with persistent symptoms. A significant minority would offer LT4 to euthyroid women with positive TPOAb and infertility and to euthyroid patients with progressive simple goitre. Alternative LT4 formulations like liquid solution or soft-gel capsules are largely reserved for specific conditions (interfering drugs, actual or suspected malabsorption, inability to take LT4 in the fasting state, unexplained poor biochemical control of hypothyroidism).

Liquid and softgel capsules of l-thyroxine results lower serum thyrotropin levels more than tablet formulations in hypothyroid patients

Objective

Evidence indicates that L-T4 in liquid and softgel capsule are absorbed better than tablets in hypothyroid patients, even when patients are under medications that impair the intestinal absorption of L-T4. However, no study has evaluated all three L-T4 formulations in the same hypothyroid patients. This study aims to fill this gap. The outcome was the degree of TSH change in the liquid and softgel formulations, using tablet L-T4 as the reference, regardless of sequence of formulation and regardless of whether patients were co-ingesting with interfering medications.

Methods

We recorded serum TSH levels in two groups of L-T4 replaced patients with primary hypothyroidism (23 subjects who did not co-ingest interfering medications, and 20 subjects who did). Either group of patients took one formulation of L-T4 at a time with variable sequences. In the first group, the median durations of exposure to tablet, liquid or softgel L-T4 were 14, 9 and 10 months, respectively. In the second group the corresponding durations were 13, 11 and 10 months, during which patients co-ingested interfering medications.

Results

In the 23 patients, there were 78, 74 or 101 TSH determinations during liquid, softgel capsule or tablet L-T4 regimens. Serum TSH levels associated with liquid, capsule or tablet L-T4 were 1.62 ± 0.51, 1.77 ± 0.44 mU/L (P = 0.049 vs liquid) or 2.38 ± 0.69 mU/L (P < 0.0001 vs liquid or capsule). Rates of TSH ≤ 2.50 mU/L were 97.4% (liquid), 95.9% (softgel) or 64.4% (tablet, P < 0.0001 vs liquid or capsule). Rates of TSH ≤ 4.12 mU/L were 100%, 100% or 98.0%.

In the 20 patients, the corresponding TSH determinations were 56, 57 and 41, and corresponding TSH levels were 2.74 ± 0.98, 2.70 ± 0.79 or 7.53 ± 2.82 mU/L. Rates of TSH ≤ 2.50 mU/L were 51.8% (liquid), 47.4% (capsule, P = 0.64) or 2.4% (tablet, P < 0.0001 vs liquid or capsule). Rates of TSH ≤ 4.12 mU/L were 92.8% (liquid), 94.7% (capsule, P = 0.68) or 12.2% (tablet, P < 0.0001 vs liquid or capsule).

Conclusions

L-T4 ingested as liquid solution or softgel capsule is more bioavailable compared to L-T4 ingested as tablet, and it is slightly superior to capsule L-T4 only in the absence of co-ingestion of interfering medications.

Hashimotos' thyroiditis: Epidemiology, pathogenesis, clinic and therapy

Hashimoto's thyroiditis (HT), the most frequent autoimmune thyroid disorders (AITDs), is the leading cause of hypothyroidism in the iodine-sufficient areas of the world. About 20-30% of patients suffers from HT, whose cause is thought to be a combination of genetic susceptibility and environmental factors that causes the loss of immunological tolerance, with a consequent autoimmune attack to the thyroid tissue and appearance of the disease. The pathologic features of lymphocytic infiltration, especially of T cells, and follicular destruction are the histological hallmark of autoimmune thyroiditis (AIT), that lead to gradual atrophy and fibrosis. An important role in the immune-pathogenesis of AITDs is due to chemokines and cytokines. In about 20% of patients, AITDs are associated with other organ specific/systemic autoimmune disorders. Many studies have demonstrated the relationship between papillary thyroid cancer and AITD. The treatment of hypothyroidism, as result of AIT, consists in daily assumption of synthetic levothyroxine.

Increased Paracetamol Bioavailability after Sleeve Gastrectomy: A Crossover Pre- vs. Post-Operative Clinical Trial

Oral drug bioavailability may be significantly altered after laparoscopic sleeve gastrectomy (LSG), the most popular bariatric procedure worldwide. Paracetamol (acetaminophen) is the post-bariatric analgesic/antipyretic drug of choice. In this work we studied and analyzed the LSG effects on systemic bioavailability and pharmacokinetics of paracetamol after oral administration of solid vs. liquid dosage form. A 4-armed, pharmacokinetic, crossover trial was performed in patients enrolled for LSG. Single paracetamol dose (500 mg), as caplet (n = 7) or syrup (n = 5), was administered before vs. 4–6 months post-LSG. Bioavailability was enhanced after LSG; in the caplet groups, average AUC_0–t increased from 9.1 to 18.6 µg·h/mL with AUC_0–t difference of 9.5 µg·h/mL (95% CI 4.6–14.5, p = 0.003). C_max increased from 1.8 (95% CI 1.2–2.5) to 4.2 µg/mL (3.6–4.8) after LSG (p = 0.032). In the syrup groups, AUC_0–t increased from 13.4 to 25.6 µg·h/mL, with AUC_0–t difference of 12.2 µg·h/mL (95% CI 0.9–23.5, p = 0.049). C_max changed from 5.4 (95% CI 2.5–8.4) to 7.8 µg/mL (6.1–9.6), and systemic bioavailability was complete (102%) after the surgery. Overall, decreased paracetamol exposure in obesity, with recovery to normal drug levels (caplet) or even higher (syrup) post-LSG, was revealed. In conclusion, attention to paracetamol effectiveness/safety in obesity, and after bariatric surgery, is prudent.

Hypothyroidism following gastric sleeve surgery resolved by ingesting crushed thyroxine tablets

Bariatric procedures for weight loss have increased in the past few decades. Levothyroxine malabsorption has been reported following gastric bypass; however, few studies have addressed this issue after gastric sleeve procedures. Levothyroxine dosing is usually weight based and administered at approximately 1.6 μg/kg body weight. Absorption occurs mainly in the jejunum and upper ileum, which can be altered by gastric pH, other drugs, food, and other factors. We present a 35-year-old woman with longstanding iatrogenic hypothyroidism treated with thyroxine, whose thyroid-stimulating hormone level rose following a gastric sleeve procedure despite taking levothyroxine daily.

Novel thyroxine formulations: a further step toward precision medicine

Levothyroxine (T4) is a critical-dose drug, because little variations in the blood concentration may cause treatment failure as well as iatrogenic thyrotoxicosis. Despite the dose response of this drug being more carefully titrated nowadays, several papers still report that a significant fraction of patients treated with levothyroxine demonstrate a TSH which is not on target. Moreover, some widespread gastrointestinal disorders as well as interfering drugs and foods may cause the "refractoriness" of a significant number of patients to an expected dose of thyroxine. The increasing awareness of the mechanisms interfering with the oral thyroid hormone bioavailability and the body of evidence regarding the complexity of treatment in certain classes of patients prompted pharmaceutical research to identify new hormonal formulations to optimize the performance of this drug. In this brief review, the progression of the scientific knowledge of novel T4 formulations use has been analyzed.

Levothyroxine Formulations: Pharmacological and Clinical Implications of Generic Substitution

Oral levothyroxine (LT4) is the standard therapy for patients with hypothyroidism. Oral LT4 is available in several formulations, including tablets, soft gel capsules and oral solution. Multiple brand-name and generic LT4 tablets are available. In the US, the Food and Drug Administration (FDA) has developed a protocol for establishing bioequivalence of LT4 formulations based on serum thyroxine (T4) levels after a single oral dose administered to healthy volunteers. This protocol has been criticized by professional endocrinology associations for using healthy individuals and ignoring serum thyroid-stimulating hormone (TSH) levels. In addition, the protocol did not initially correct for baseline T4 levels, although this was changed in a later version. There are concerns that the FDA's protocol could allow products with clinically significant differences in bioavailability to be declared therapeutically equivalent and interchangeable. Once a generic LT4 has been shown to be bioequivalent to a brand-name LT4, it may be substituted for that brand-name LT4 with no need for dose adjustment or follow-up therapeutic monitoring. Often, the substitution is made by the pharmacy without the physician's knowledge. Even small differences between LT4 formulations can cause significant changes in TSH levels. This may be a particular concern in vulnerable populations, including elderly, pregnant, and pediatric patients. Problems that can be encountered when switching between formulations or when original products are reformulated are discussed in this review. These problems include altered efficacy and adverse events, some of which can be caused by excipients. Patients should be maintained on the same LT4 preparation if possible. If the LT4 preparation is changed, TSH levels should be evaluated and, if necessary, the dose of LT4 adjusted.Funding: Merck.Plain Language Summary: Plain language summary available for this article.

Levothyroxine Dose Adjustment to Optimise Therapy Throughout a Patient's Lifetime

Levothyroxine is the standard therapy for patients with hypothyroidism, a condition that affects up to 5% of people worldwide. While levothyroxine therapy has substantially improved the lives of millions of hypothyroid patients since its introduction in 1949, the complexity of maintaining biochemical and clinical euthyroidism in patients undergoing treatment with levothyroxine cannot be underestimated. Initial dosing of levothyroxine can vary greatly and may be based on the amount of residual thyroid function retained by the patient, the body weight or lean body mass of the patient, and thyroid-stimulating hormone levels. As levothyroxine is usually administered over a patient's lifetime, physiological changes throughout life will affect the dose of levothyroxine required to maintain euthyroidism. Furthermore, dose adjustments may need to be made in patients with concomitant medical conditions, in patients taking certain medications, as well as in elderly patients. Patients who have undergone any weight or hormonal changes may require dose adjustments, and the majority of pregnant women require increased doses of levothyroxine. Optimal treatment of hypothyroidism requires a partnership between patient and physician. The physician is tasked with vigilant appraisal of the patient's status based on a thorough clinical and laboratory assessment and appropriate adjustment of their levothyroxine therapy. The patient in turn is tasked with medication adherence and reporting of symptomatology and any changes in their medical situation. The goal is consistent maintenance of euthyroidism, without the patient experiencing the adverse events and negative health consequences of under- or overtreatment.Funding Merck.Plain Language Summary Plain language summary available for this article.

Major imbalance of thyroid function after laparoscopic sleeve gastrectomy

In patients with substituted hypothyroidism, laparoscopic sleeve gastrectomy may interfere with thyroid balance by varying body weight or by altering the absorption of hormone therapy. A 58-year-old female patient presented with a major thyroid imbalance after sleeve gastrectomy, manifesting itself in large-scale changes in thyroid stimulating hormone (TSH) levels. The transition from a tablet treatment to a liquid form alleviated burden of treatment, unfortunately without normalising TSH. Our case emphasises the importance of the understanding of hypothalamic-pituitary-thyroid feedback control mechanisms together with good galenic choice, management of associated conditions and the elimination of other causes of variations of TSH levels during the management of hypothyroid patients after sleeve gastrectomy.

Expression of miRNA-146b-5p in patients with thyroid cancer in combination with Hashimoto's disease and its clinical significance

The expression level of microRNA (miRNA)-146b in patients with thyroid carcinoma (TC) in combination with Hashimoto's thyroditis (HT) was evaluated to analyze the clinical significance. Eighty-seven patients who underwent thyroid surgery in The Third Affiliated Hospital of Southern Medical University from March 2010 to February 2013 were enrolled. Of the patients, 37 were diagnosed with TC (group A), and 50 were diagnosed with TC in combination with HT (group B). Forty patients were diagnosed with HT (group C). The expression levels of miRNA-146b-5p in cancer tissue and paracancerous tissue of patients in the two groups were measured by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Correlation between the miRNA-146b-5p levels and the clinicopathological characteristics of patients with combined TC and HT were evaluated. According to the expression of miRNA-146b-5p, patients in group B were separated into the high and low expression groups to observe the five-year cancer recurrence rate. There was no significant difference in miRNA-146b-5p expression between the papillary carcinoma group, the follicular carcinoma group and the medullary carcinoma group (P>0.05). The miRNA-146b-5p expression in the lesion tissue of group B was significantly higher than that of groups A and C, while the miRNA-146b-5p expression in the lesion tissue of group A was significantly higher than that of group C (P<0.05), and the lesion tissue of the three groups was higher than that of the corresponding parastatal tissue (P<0.05). The miRNA-146b-5p expression level was associated with tumor size, lymph node metastasis and TNM stage (P<0.05), while not associated with sex, age, lesion multiplicity, smoking history, diabetes history and pathological type in group B (P>0.05). The non-recurrence rate of group B high expression subgroup was lower than that of group B low expression subgroup (P=0.045). High expression of miRNA-146b-5p was found in the cancer tissues of patients with combined TC and HT. The expression level of miRNA-146b-5p was associated with tumor size, lymph node metastasis and TNM stage. It is a potential prognostic indicator for patients with combined TC and HT.

Effect of Weight Loss after Bariatric Surgery on Thyroid-Stimulating Hormone Levels in Euthyroid Patients with Morbid Obesity

Obesity is associated with several endocrine abnormalities, including thyroid dysfunction. The objective of this study was to investigate the effect of weight loss after bariatric surgery on thyroid-stimulating hormone (TSH) levels in euthyroid patients with morbid obesity. We performed an observational study, evaluating patients with morbid obesity submitted to bariatric surgery. We included 129 patients (92 women) and 31 controls (21 women). Clinical, anthropometric, biochemical, and hormonal parameters were evaluated. The primary endpoint was circulating TSH (µU/mL). Fasting TSH levels were higher in the obese group (3.3 ± 0.2) than in the control group (2.1 ± 0.2). The mean excessive body mass index (BMI) loss (EBMIL) 12 months after bariatric surgery was 72.7 ± 2.1%. TSH levels significantly decreased in the obese patients after surgery; 3.3 ± 0.2 vs. 2.1 ± 0.2 before and 12 months after surgery, respectively. Free thyroxine (T4) (ng/dL) levels significantly decreased in the obese patients after surgery; 1.47 ± 0.02 vs. 1.12 ± 0.02 before and 12 months after surgery, respectively. TSH decreased significantly over time, and the decrement was associated with the EBMIL. In euthyroid patients with morbid obesity, weight loss induced by bariatric surgery promotes a significant decline of the increased TSH levels. This decrement of TSH is progressive over time after surgery and significantly associated with excess BMI loss.

Gastrointestinal Malabsorption of Thyroxine

Levothyroxine, a largely prescribed drug with a narrow therapeutic index, is often a lifelong treatment. The therapeutic efficacy of T4 may be marred by behavioral, pharmacologic, and pathologic issues acting as interfering factors. Despite a continuous search for an optimal T4 treatment, a significant number of patients fail to show a complete chemical and/or clinical response to this reference dose of T4. Gastrointestinal malabsorption of oral T4 represents an emerging cause of refractory hypothyroidism and may be more frequent than previously reputed. In this review, we examine the pharmacologic features of T4 preparations and their linkage with the intestinal absorption of the hormone. We have stressed the major biochemical and pharmacologic characteristics of T4 and its interaction with the putative transporter at the intestinal level. We have examined the interfering role of nutrients, foods, and drugs on T4 absorption at the gastric and intestinal levels. The impact of gastrointestinal disorders on T4 treatment efficacy has been also analyzed, in keeping with the site of action and the interfering mechanisms. Based on the evidence obtained from the literature, we also propose a schematic diagnostic workup for the most frequent and often hidden gastrointestinal diseases impairing T4 absorption.

Oral levothyroxine therapy postbariatric surgery: Biopharmaceutical aspects and clinical effects

BACKGROUND

Bariatric surgery can lead to changes in the oral absorption of many drugs. Levothyroxine is a narrow therapeutic drug for hypothyroidism, a common condition among patients with obesity.

OBJECTIVE

The purpose of this work was to provide a mechanistic overview of levothyroxine absorption, and to thoroughly analyze the expected effects of bariatric surgery on oral levothyroxine therapy.

METHODS

We performed a systematic review of the relevant literature reporting the effects of bariatric surgery on oral levothyroxine absorption and postoperative thyroid function. A PubMed search for relevant keywords resulted in a total of 14 articles reporting levothyroxine status before versus after bariatric surgery.

RESULTS

Different mechanisms may support opposing trends as to levothyroxine dose adjustment postsurgery. On the one hand, based on impaired drug solubility/dissolution attributable to higher gastric pH as well as reduced gastric volume, compromised levothyroxine absorption is expected. On the other hand, the great weight loss, and altered set-point of thyroid hormone homeostasis with decreased thyroid-stimulating hormone after the surgery, may result in a decreased dose requirement.

CONCLUSIONS

For patients after bariatric surgery, close monitoring of both the clinical presentation and plasma thyroid-stimulating hormone and T4 levels is strongly advised. Better understanding and awareness of the science presented in this article may help to avoid preventable complications and provide optimal patient care.

Decreased Leptin Is Associated with Alterations in Thyroid-Stimulating Hormone Levels after Roux-en-Y Gastric Bypass Surgery in Obese Euthyroid Patients with Type 2 Diabetes

BACKGROUND

Leptin has been shown to stimulate the hypothalamus-pituitary-thyroid (HPT) axis in vivo and vitro. Its role in thyroid axis regulation after weight loss induced by bariatric surgery is still unknown. The aim of this study was to evaluate the influence of leptin on weight loss and thyroid function variation induced by Roux-en-Y gastric bypass (RYGB) surgery in euthyroid individuals with obesity and type 2 diabetes mellitus (T2DM).

METHODS

65 Chinese individuals with obesity and T2DM who underwent RYGB, and 27 healthy volunteers were enrolled in this retrospective study. Participants were evaluated for changes in anthropometric parameters, metabolic indexes, thyroid function, and leptin levels before and 12 months after surgery.

RESULTS

After RYGB, all of these patients experienced significant weight reduction and improved glucose control. Metabolic parameters were significantly ameliorated after surgery compared with baseline. Thyroid hormones including free triiodothyronine (FT3), free thyroxine (FT4), and thyroid-stimulating hormone (TSH) declined in parallel. Median (IQR) plasma leptin levels decreased from 33.7 ng/mL (17.9-63.1) to 10.3 ng/mL (4.0-18.5). Pearson correlation analysis showed that TSH was significantly positively correlated with body mass index, C-reactive protein (CRP), and leptin. Multiple stepwise linear regression indicated that leptin and CRP were independent factors affecting TSH. The β coefficients were 0.38 (p = 0.001) and 0.32 (p = 0.004), respectively. There was a significant positive correlation between ΔTSH and Δleptin (r = 0.33, p = 0.01).

CONCLUSION

Decreased or normalized TSH levels after weight loss induced by RYGB might be mediated by the decline in leptin. There could be cross talk between adipose tissue and the HPT axis.

Oral L-thyroxine liquid versus tablet in patients submitted to total thyroidectomy for thyroid cancer (without malabsorption): A prospective study

Objective

No consistent data are present in literature about the effectiveness of Levothyroxine (L‐T4) liquid formulation in patients without malabsorption after thyroidectomy. The aim of this study is to compare the effectiveness of L‐T4 liquid formulation, with L‐T4 tablets, in thyroid cancer patients after thyroidectomy (without malabsorption or drug interference).

Methods

One hundred five patients were recruited; 52 patients were treated with liquid L‐T4 formulation, while 53 with L‐T4 tablets, at the same dosage (1.5 mcg/kg/day). Patients started to assume the drug the day after surgery, 30 min before breakfast. In both groups circulating levels of thyrotropic hormone (TSH), free thyroxine (FT4), and free triiodothyronine (FT3) were dosed at week 6 (first control), and then at week 12 (second control).

Results

We obtained significantly lower TSH values in the liquid L‐T4 group patients, compared to the tablet L‐T4 group, at the first control (P < .05), and at the second control (P < .01), while FT4 and FT3 levels were not significantly different. Hypothyroid range (TSH > 3.6 mcU/mL) was significantly more prevalent in the patients treated with L‐T4 tablet.

Conclusions

A better control of TSH was observed in thyroidectomized patients (without malabsorption, gastric disorders, or drug interference) with liquid L‐T4 regimen.

Level of Evidence

2c–Outcomes Research

Pharmacokinetics and Comparative Bioavailability of a Levothyroxine Sodium Oral Solution and Soft Capsule

A new formulation of levothyroxine sodium has been developed in the form of an oral solution contained in unit‐dose ampules. A study has been conducted to compare the bioavailability of levothyroxine sodium oral solution and levothyroxine sodium soft capsule in healthy volunteers under fasting conditions. The rate and extent of absorption of the new levothyroxine solution were also evaluated when administered on dilution in water or directly into the mouth without water. In each period, according to the randomization scheme, subjects were administered single oral doses of either test, as 4 × 150‐μg unit‐dose ampules, with or without water, or reference, as 4 × 150‐μg capsules in a crossover design. Thirty‐six subjects were randomized and dosed in this study; of these, 31 completed all study periods. When comparing the solution with the capsule (both products administered with water), the 90% confidence intervals for the ratio of log‐transformed values of AUC_0‐48 and C_max were within 90.00% and 111.11%, respectively, for baseline‐corrected levothyroxine. Moreover, the administration of levothyroxine oral solution without water did not affect the rate and extent of its absorption. In conclusion, levothyroxine oral solution unit‐dose ampules were bioequivalent to the levothyroxine capsule when administered with or without water. All formulations were well tolerated, with no major side effects.

Systematic review of drug bioavailability following gastrointestinal surgery

PURPOSE

Inter- and intraindividual pharmacokinetics variability in humans affects the way in which drugs act on the body. Gastrointestinal surgery has an impact on this variability and significantly alters the kinetics of drugs in post-surgical patients. The way in which pharmacokinetic profiles are modified depends on the type of operative procedure performed. The extent to which the absorption of different groups of drugs is affected varies according to the site and length of intestinal resections.

METHODS

A literature search was conducted based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol. Three databases were searched: MEDLINE, Embase, and the Cochrane Library. For each drug, potential changes in absorption were described, including recommendations extracted from the results of the studies and collected according to authors' criteria as practical conclusions, and grades of recommendation were determined by levels of evidence using the Oxford Centre for Evidence-Based Medicine scale.

RESULTS

Sixty-eight articles were collected during the selection process after the bibliographic search. The main outcomes for 60 drugs from the various studies were classified according to each type of surgery.

CONCLUSIONS

Modifications in the digestive tract secondary to gastrointestinal surgery may compromise the bioavailability of drugs. Decreased absorption surface, gastric emptying speed, and gastric pH alteration are factors to be taken into account in the management of pharmacological treatment after surgery. Evidence supported by data in clinical practice is scarce, but after studying the pharmacokinetic profile of some molecules, it is possible to offer recommendations for its adaptation to the patient's clinical situation.

Liquid L-thyroxine versus tablet L-thyroxine in patients on L- thyroxine replacement or suppressive therapy: a meta-analysis

PURPOSE

To compare the effectiveness of liquid L-T4 (L-thyroxine) and tablet L-T4 in patients on L-T4 replacement or suppressive therapy.

METHODS

The Cochrane Library, PubMed, Embase, and Web of Science databases were searched to identify relevant articles. All prospective or randomized controlled studies (RCTs) comparing liquid L-T4 and tablet L-T4 in patients on L-T4 replacement or suppressive therapy were included in the analysis.

RESULTS

Overall, the initial search of the four databases identified 1278 published studies; of these, eight studies were ultimately included in the meta-analysis. TSH (thyroid stimulating hormone) levels were significantly suppressed in patients on liquid L-T4 compared with those on tablet L-T4, in patients on L-T4 suppressive therapy with L-T4 malabsorption (Mean Difference (MD) = -2.26, 95% Confidence Interval (CI): -3.59, -0.93; P = 0.0009)). However, liquid L-T4 and tablet L-T4 did not show a statistically significant difference in patients on L-T4 suppressive therapy without malabsorption (MD = 0.08, 95% CI: -0.31, 0.47; P = 0.69). TSH levels were significantly normalized in patients on liquid L-T4 compared with those on tablet L-T4, in Patients on L-T4 replacement therapy with L-T4 malabsorption (MD = -3.20, 95% CI: -5.08, -1.32; P = 0.0009). However, liquid L-T4 and tablet L-T4 did not show a statistically significant difference in patients on L-T4 replacement therapy without malabsorption (MD = 0.91, 95% CI: -0.03, 1.86; P = 0.06).

CONCLUSION

Liquid L-T4 is more efficient than tablet L-T4 in patients on L-T4 replacement or suppressive therapy with malabsorption. No significant differences were observed in patients without malabsorption. Further studies should be conducted to verify these findings.