Oral liquid levothyroxine treatment at breakfast: a mistake?

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.

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.

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.

Medications and Food Interfering with the Bioavailability of Levothyroxine: A Systematic Review

Purpose

Levothyroxine is a common prescribed drug. Many medications and food, however, can interfere with its bioavailability. The aim of this review was to summarize the medications, food and beverages that interact with levothyroxine and to assess their effects, mechanisms and treatments.

Methods

A systematic review on interfering substances that interact with levothyroxine was performed. Web of Science, Embase, PubMed, the Cochrane library, grey literature from other sources and the lists of references were searched for human studies comparing the levothyroxine efficacy with and without interfering substances. The patient characteristics, drug classes, effects and mechanism were extracted. The NHLBI study quality assessment tools and the JBI critical appraisal checklist were used to assess the quality of included studies.

Results

A total of 107 articles with 128 studies were included. Drugs interactions were revealed in calcium and iron supplements, proton pump inhibitors, bile acid sequestrants, phosphate binders, sex hormones, anticonvulsants and other drugs. Some food and beverage could also induce malabsorption. Proposed mechanisms included direct complexing, alkalization, alteration of serum thyroxine-binding globulin levels and acceleration of levothyroxine catabolism via deiodination. Dose adjustment, administration separation and discontinuation of interfering substances can eliminate the interactions. Liquid solutions and soft-gel capsules could eliminate the malabsorption due to chelation and alkalization. The qualities of most included studies were moderate.

Conclusion

Lots of medications and food can impair the bioavailability of levothyroxine. Clinicians, patients and pharmaceutical companies should be aware of the possible interactions. Further well-designed studies are needed to provide more solid evidence on treatment and mechanisms.

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.

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.

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.

Concomitant Use of Levothyroxine and Proton Pump Inhibitors in Patients with Primary Hypothyroidism: a Systematic Review

BACKGROUND

The aim of this study was to assess the effect of concomitant use of levothyroxine (LT4) and proton pump inhibitors (PPIs) on thyroid-stimulating hormone (TSH) levels in patients with primary hypothyroidism.

METHODS

A systematic review of interventional and observational studies that compared the TSH levels before and after concomitant use of LT4 and PPI was performed. Articles published in English up to September 1, 2019, were included. PubMed, EMBASE, and Cochrane Library databases. Gray literature was also searched in repositories, websites OpenGrey and Google Scholar, and abstracts of major international congresses. Study quality was assessed with the Newcastle-Ottawa quality assessment scale for observational studies and the Risk Of Bias In Non-randomized Studies - of Interventions (ROBINS-I) tool was used.

RESULTS

Five thousand twelve discrete articles were identified. Following assessment and application of eligibility criteria, seven studies were included. There was a considerable heterogeneity among the included studies in design, sample size, inclusion and exclusion criteria, treatment regimen, and baseline demographics. Each of the included studies showed an increase in TSH levels following LT4 and PPI consumption, and in the majority of these, the increase was statistically significant.

DISCUSSION

The concomitant use of LT4 and PPI showed a significant increase in TSH concentration. However, given the small number of studies, further research is needed to clarify the interfering role of PPI on LT4 intestinal absorption.

PROSPERO REGISTRATION NUMBER

CRD42020047084.

Levothyroxine Interactions with Food and Dietary Supplements-A Systematic Review

Levothyroxine (l-thyroxine, l-T4) is a drug of choice for treating congenital and primary hypothyroidism. Although clinically significant interactions between l-T4 and food can alter the safety and efficacy of the treatment, they still seem to be generally underestimated by patients, physicians and pharmacists. This review aimed to investigate the effects of meals, beverages, and dietary supplements consumption on l-T4 pharmacokinetics and pharmacodynamics, to identify the most evident interactions, and to perform the recommendations for safe co-administering of l-T4 and food. A total of 121 studies were identified following a systematic literature search adhering to PRISMA guidelines. After full-text evaluation, 63 studies were included. The results proved that l-T4 ingestion in the morning and at bedtime are equally effective, and also that the co-administration of l-T4 with food depends on the drug formulation. We found limited evidence for l-T4 interactions with coffee, soy products, fiber, calcium or iron supplements, and enteral nutrition but interestingly they all resulted in decreased l-T4 absorption. The altered l-T4 efficacy when ingested with milk, juices, papaya, aluminium-containing preparations, and chromium supplements, as well as observed enhancement effect of vitamin C on l-T4 absorption, shall be further investigated in larger, well-designed studies. Novel formulations are likely to solve the problem of coffee, calcium and iron induced malabsorption of l-T4. Maintaining a proper time interval between l-T4 and food intake, especially for coffee and calcium, or iron supplements, provides another effective method of eliminating such interactions.

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.

Stability and Compatibility Studies of Levothyroxine Sodium in Solid Binary Systems-Instrumental Screening

The influence of excipients on the stability of sodium levothyroxine pentahydrate (LTSS) under ambient conditions and thermal stress was evaluated. Since LTSS is a synthetic hormone with a narrow therapeutic index, the interactions of LTSS with excipients can lead to a drastic diminution of therapeutic activity. Ten commonly used pharmaceutical excipients with different roles in solid formulations were chosen as components for binary mixtures containing LTSS, namely, starch, anhydrous lactose, D-mannitol, D-sorbitol, gelatin, calcium lactate pentahydrate, magnesium stearate, methyl 2-hydroxyethyl cellulose (Tylose), colloidal SiO₂ (Aerosil) and talc. As investigational tools, universal attenuated total reflectance- Fourier transform infrared spectroscopy UATR-FTIR spectroscopy and thermal analysis were chosen and used as follows: UATR-FTIR spectra were drawn up for samples kept under ambient conditions, while thermoanalytical tools (TG/DTG/HF data) were chosen to evaluate the inducing of interactions during thermal stress. The corroboration of instrumental results led to the conclusion that LTSS is incompatible with lactose, mannitol and sorbitol, and these excipients should not be considered in the development of new generic solid formulations.

Environmental photochemical fate and UVC degradation of sodium levothyroxine in aqueous medium

The synthetic hormone sodium levothyroxine (LTX) is one of the most prescribed drugs in the world and the most effective in hypothyroidism treatment. The presence of LTX in the environment has become a matter of major concern due to the widespread use of this hormone and by the fact that it is only partially removed in conventional water and sewage treatment plants. However, information regarding the photochemical fate of this hormone in environmental or engineered systems is scarce in the literature. In this work, the sunlight-driven direct and indirect LTX degradation was investigated by determining the photolysis quantum yield, Φ_LTX = 3.80 (± 0.02) × 10^-5, as well as the second-order kinetic constants of the reactions with hydroxyl radicals, k_LTX,•OH = 1.50 (± 0.01) × 10¹⁰ L mol^-1 s^-1 and singlet oxygen, k_LTX,1O2 = 1.47 (± 0.66) × 10⁸ L mol^-1 s^-1. Mathematical simulations indicate that LTX photodegradation is favored in shallow, nitrite-rich, and dissolved organic matter (DOM)-poor environments, with LTX half-life times varying from less than 10 days to about 80 days. LTX removals of 85 and 95% were achieved by UVC photolysis and UVC/H₂O₂ after 120 min, respectively. Three transformation products, triiodothyronine, diiodothyronine, and diiodotyrosine, were identified during LTX degradation by the UVC-based processes studied. The results herein regarding photo-induced kinetics coupled with environmental fate simulations may help evaluate LTX persistence and also the design of water and wastewater treatment processes.

Shift from Levothyroxine Tablets to Liquid Formulation at Breakfast Improves Quality of Life of Hypothyroid Patients

Background: Until recently, treatment of hypothyroidism has been accomplished using monotherapy of synthetic L-thyroxine (L-T4) sodium tablets that should be taken 30-60 minutes before breakfast. Nowadays, a liquid preparation of levothyroxine is available and can effectively replace tablets without the need of waiting before having breakfast. Evidence of Quality of life (QoL) improvement when shifting from the former to the latter preparation, however, is still lacking.

Objective: The study aimed to assess changes in QoL of hypothyroid patients dissatisfied with their therapy with L-T4 sodium tablets who were switched from tablets taken 30-60 minutes before breakfast to liquid L-T4 at breakfast.

Methods: A total of 418 consecutive hypothyroid subjects treated by means of L-T4 tablets were asked about their satisfaction/dissatisfaction in order to take the medication 30-60 minutes before having breakfast. Overall, 110 patients (26.3%) complained of the timing of their L-T4 therapy (30-60 minutes before breakfast). A dedicated QoL questionnaire (ThyTSQ), taking just a few minutes to be filled in was then administered to these dissatisfied patients. They were therefore switched to L-T4 to be taken at breakfast. Aiming to avoid TSH elevation due to L-T4 tablets malabsorption caused by meal interference and gastric pH changes, patients were invited to take L-T4 liquid form, as this is claimed to be scarcely affected by the non-fasting state. The questionnaire (ThyTSQ) was administered again at the control visit 3 months later. TSH, FT4, FT3 serum concentrations and metabolic parameters were also recorded.

Results: An improved QoL, mainly due to an easier adherence to treatment, was reported by 66.6% of 102 patients who completed the study after shifting from taking medication 30-60 minutes before breakfast to at breakfast ingestion (P<0.01). An overall 10.7% of patients found the liquid formulation distasteful. Mean values of TSH, FT4, FT3, and of metabolic parameters did not significantly change but in eight patients (7.7%) who showed a TSH increase > 2mIU/L

Conclusion: In hypothyroid subjects dissatisfied with L-T4 tablets ingested 30-60 minutes before breakfast, the shift to the same dose of L-T4 in liquid form taken at breakfast improved QoL in the majority of patients, without affecting thyroid function.

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.

Levothyroxine Therapy: Changes of TSH Levels by Switching Patients from Tablet to Liquid Formulation. A Systematic Review and Meta-Analysis

BACKGROUND

In the last years, levothyroxine (LT4) has been commercialized also in liquid formulation, which is less sensitive to the factors known to reduce the absorption of tablet LT4. To date, there is no robust information that liquid LT4 can improve pharmacologic thyroid homeostasis of patients with reduced efficacy of tablet LT4. This analysis aimed at achieving solid evidence that switching thyroxine treatment from tablet to liquid preparation improves patients' TSH levels.

METHODS

The search was performed in PubMed/MEDLINE and Scopus database based on the terms "thyroid," "levothyroxine," and "liquid," and updated until September 25, 2017. Studies were included only if they described patients with suboptimal TSH on tablet LT4, subsequently switched to liquid LT4.

RESULTS

The literature search retrieved 462 articles and six were finally included. The pooled mean difference of TSH value between tablet and liquid LT4 was 4.23 mIU/L (95% CI from 3.69 to 4.77). Mild heterogeneity was found (I₂ 60%). Overall mean difference of TSH was significant (p < 0.0001).

CONCLUSION

The present meta-analysis showed that patients with suboptimal TSH on tablet LT4 can have a significantly improved TSH by switching to liquid LT4 formulation at unchanged dose.

Urinary metabolomics reveals glycemic and coffee associated signatures of thyroid function in two population-based cohorts

Background

Triiodothyronine (T3) and thyroxine (T4) as the main secretion products of the thyroid affect nearly every human tissue and are involved in a broad range of processes ranging from energy expenditure and lipid metabolism to glucose homeostasis. Metabolomics studies outside the focus of clinical manifest thyroid diseases are rare. The aim of the present investigation was to analyze the cross-sectional and longitudinal associations of urinary metabolites with serum free T4 (FT4) and thyroid-stimulating hormone (TSH).

Methods

Urine Metabolites of participants of the population-based studies Inter99 (n = 5620) and Health2006/Health2008 (n = 3788) were analyzed by ¹H-NMR spectroscopy. Linear or mixed linear models were used to detect associations between urine metabolites and thyroid function.

Results

Cross-sectional analyses revealed positive relations of alanine, trigonelline and lactic acid with FT4 and negative relations of dimethylamine, glucose, glycine and lactic acid with log(TSH). In longitudinal analyses, lower levels of alanine, dimethylamine, glycine, lactic acid and N,N-dimethylglycine were linked to a higher decline in FT4 levels over time, whereas higher trigonelline levels were related to a higher FT4 decline. Moreover, the risk of hypothyroidism was higher in subjects with high baseline trigonelline or low lactic acid, alanine or glycine values.

Conclusion

The detected associations mainly emphasize the important role of thyroid hormones in glucose homeostasis. In addition, the predictive character of these metabolites might argue for a potential feedback of the metabolic state on thyroid function. Besides known metabolic consequences of TH, the link to the urine excretion of trigonelline, a marker of coffee consumption, represents a novel finding of this study and given the ubiquitous consumption of coffee requires further research.

Comparative study between the effects of replacement therapy with liquid and tablet formulations of levothyroxine on mood states, self-perceived psychological well-being and thyroid hormone profile in recently thyroidectomized patients

Following thyroid surgery, levothyroxine therapy is used to replace deficient thyroid hormones and prevent postoperative thyroid hypofunction. We compared the effects of replacement therapy with either liquid or tablet formulation of levothyroxine on mood states, self-perceived mental well-being and thyroid hormone profile in recently thyroidectomized patients. Profile of mood states, General Heath Questionnaire 12-items and thyroid hormone profile were assessed in recently (5-7 days) thyroidectomized patients at baseline and 2 months after randomization to replacement therapy with either liquid (n = 77) or tablet (n = 78) formulation of levothyroxine. After 2 months under levothyroxine replacement treatment, significant improvements of Positive Affect Scale (p < 0.001) and Negative Affect Scale (p < 0.001) of Profile of mood states, as well as of General Heath Questionnaire 12-items (p < 0.001) were observed in the study population. However, there were greater variations observed in patients assigned to liquid levothyroxine formulation in comparison to those who were assigned to levothyroxine in the form of tablet (time × treatment interaction: Positive Affect Scale of Profile of mood states, p = 0.030; Negative Affect Scale of Profile of mood states, p < 0.0001; General Heath Questionnaire 12-items, p = 0.003). As expected, circulating TSH levels significantly decreased (p <0.001) while FT3 and FT4 levels significantly increased (p < 0.0001 for both) under levothyroxine replacement therapy. These changes were significantly greater in patients treated with liquid levothyroxine formulation (time × treatment interaction: TSH, p = 0.011; FT3, p = 0.016; FT4, p = 0.028). Our data indicate a greater efficacy of liquid formulation of levothyroxine in ameliorating mood states and self-perception of mental well-being and thyroid hormone profile after 2 months of replacement therapy in recently thyroidectomized patients.

Liquid and softgel levothyroxine use in clinical practice: state of the art

Levothyroxine is recognized as the treatment of choice for hypothyroidism. So far, the tablet levothyroxine has been the formulation almost exclusively used, even though an optimal daily dose of levothyroxine has been unsuccessfully sought and a consensus not achieved. Due to progressive use of a more individually tailored levothyroxine dose, increasing evidence has instead displayed that many gastrointestinal disorders, polypharmacy, and food interference may raise the daily levothyroxine requirement. In recent years, alternative levothyroxine formulations have become available and have rapidly gained attention because of their pharmacokinetic properties. This study aims to provide an overview regarding the use of softgel capsule and/or liquid levothyroxine solution while performing a review of published studies about such topic. A comprehensive computer literature search of the PubMed/MEDLINE, Scopus, and Google Scholar databases has been conducted to find published articles on this topic. The search algorithm was based on the combinations of the following terms: "oral solution" or "soft gel" or "liquid", and "levothyroxine". The computer search resulted in 75 articles; through a critical review of such titles and abstracts and a screening of their references lists, the review included 18 original articles relating to 800 patients treated with alternative formulations. Despite some limits, the results obtained using softgel and liquid levothyroxine were consistent with each other. In selected categories of levothyroxine-treated patients (pediatric, suffering from hypo-achlorhydria, polypharmacy, undergone bariatric surgery, fed through enteric tube) these new formulations have shown promising attributes in improving a treatment that needs to be individually tailored.

Update on the treatment of hypothyroidism

PURPOSE OF REVIEW

Differentiated thyroid cancer is a malignancy that is rapidly increasing in frequency. As thyroidectomy plays a central role in the treatment of thyroid cancer, it is incumbent on physicians treating this patient group to be well versed in the intricacies of treating hypothyroidism.

RECENT FINDINGS

Treatment of hypothyroidism may be refined by careful attention to dose selection, monitoring of therapy and achievement of thyrotropin goals that are specific to the individual patient's overall clinical situation. These goals are common not only to patients with a sole diagnosis of hypothyroidism, as discussed in the recent American Thyroid Association Guidelines, but also to patients with hypothyroidism in the setting of thyroid cancer. Several recent studies have illuminated our understanding of the benefits and risks of thyrotropin suppression therapy in patients with differentiated thyroid cancer. Multiple studies of combination therapy with levothyroxine and liothyronine for treating hypothyroidism have not led to a clear conclusion about its benefits over levothyroxine monotherapy. Animal studies have advanced our understanding of the altered serum and tissue milieu that characterizes levothyroxine monotherapy. Crossing the bridge from this translational research into clinical research using sustained release triiodothyronine preparations may ultimately enhance the health of our patients.

SUMMARY

Continued refinement of our understanding of thyroid status and our ability to flawlessly implement thyroid hormone replacement is an active area of research.

Advancements in the treatment of hypothyroidism with L-T4 liquid formulation or soft gel capsule: an update

INTRODUCTION

The most recent advance concerning levothyroxine (L-T4) therapy is the development of novel oral formulations: the liquid preparation, and the soft gel capsule. Areas covered: This review evaluates the most recent clinical studies about these new formulations. The liquid formulation has been shown to overcome: the food and beverages intereference with L-T4 tablets absorption, caused by food or coffee at breakfast; malabsorption induced by the increased gastric pH, resulting from atrophic gastritis, or due to proton-pump inhibitors; and malabsorption after bariatric surgery. The use of liquid L-T4 has been studied also in pregnancy, newborns and infants, suggesting a better bioequivalence than tablets. Finally, liquid L-T4 is more active than tablets in the control of thyroid-stimulating hormone (TSH) in hypothyroid patients without malabsorption, drug interference, or gastric disorders, leading to a hypothesized higher absorption of liquid L-T4 also in these patients. Few studies have evaluated soft gel L-T4 with promising results in patients with malabsorption related to coffee or gastritis. Expert opinion: Liquid L-T4 (and soft gel capsules) are more active than the tablet L-T4 in the control of TSH in hypothyroid patients with gastric disorders, malabsorption, or drug interference, but also in patients without absorption disorders.

ITALIAN ASSOCIATION OF CLINICAL ENDOCRINOLOGISTS STATEMENT-REPLACEMENT THERAPY FOR PRIMARY HYPOTHYROIDISM: A BRIEF GUIDE FOR CLINICAL PRACTICE

OBJECTIVE

Hypothyroidism requires life-long thyroid hormone replacement therapy in most patients. Oral levothyroxine (LT4) is an established safe and effective treatment for hypothyroidism, but some issues remain unsettled.

METHODS

The Italian Association of Clinical Endocrinologists appointed a panel of experts to provide an updated statement for appropriate use of thyroid hormone formulations for hypothyroidism replacement therapy. The American Association of Clinical Endocrinologists' protocol for standardized production of clinical practice guidelines was followed.

RESULTS

LT4 is the first choice in replacement therapy. Thyroid-stimulating hormone (TSH) should be maintained between 1.0 and 3.0 mIU/L in young subjects and at the upper normal limit in elderly or fragile patients. Achievement of biochemical targets, patient well-being, and adherence to treatment should be addressed. In patients with unstable serum TSH, a search for interfering factors and patient compliance is warranted. Liquid or gel formulations may be considered in subjects with hampered LT4 absorption or who do not allow sufficient time before or after meals and LT4 replacement. Replacement therapy with LT4 and L-triiodothyronine (LT3) combination is generally not recommended. A trial may be considered in patients with normal values of serum TSH who continue to complain of symptoms of hypothyroidism only after co-existent nonthyroid problems have been excluded or optimally managed. LT3 should be administered in small (LT4:LT3 ratio, 10:1 to 20:1) divided daily doses. Combined therapy should be avoided in elderly patients or those with cardiac risk factors and in pregnancy.

CONCLUSION

LT4 therapy should be aimed at resolution of symptoms of hypothyroidism, normalization of serum TSH, and improvement of quality of life. In selected cases, the use of liquid LT4 formulations or combined LT4/LT3 treatment may be considered to improve adherence to treatment or patient well-being.

ABBREVIATIONS

AACE = American Association of Clinical Endocrinologists FT3 = free triiodothyronine FT4 = free thyroxine LT3 = levotriiodothyronine LT4 = levothyroxine MeSH = medicine medical subject headings QoL = quality of life TSH = thyroid-stimulating hormone.

Timing of breakfast does not influence therapeutic efficacy of liquid levothyroxine formulation

Oral levothyroxine (L-T4) is the mainstay of hypothyroidism treatment. Many factors may influence its absorption, including the timing of administration. Objective of the study is to demonstrate the therapeutic equivalence of administering liquid L-T4 with breakfast or 10 min before breakfast. This was a pilot study conducted with a crossover design AB/BA where A stays for L-T4 with breakfast and B for L-T4 10 min before breakfast. A post hoc analysis was conducted to compare L-T4 administered at breakfast or 10 min before breakfast with L-T4 administered 30 min before breakfast. Sixty-one hypothyroid patients were enrolled and assigned to one of the two treatment sequences. All patients were evaluated for TSH levels at the end of each period. Fifty-nine patients completed the study. The mean thyrotropin concentration was 1.52 ± 0.73 µU/ml when L-T4 was administered with breakfast and 1.46 ± 0.81 µU/ml when it was taken 10 min before breakfast, without clinically and statistically significant differences (P = 0.59), regardless of treatment sequence and period. The mean thyrotropin concentration was 1.54 ± 0.9 µU/ml when L-T4 was administered at 0-10 min intervals before breakfast and 1.25 ± 0.7 µU/ml when it was taken 30 min before breakfast (ratio = 1.23, within our definition of equivalence set at 0.8-1.25). There is therapeutic equivalence between liquid L-T4 administration at breakfast or 10 min before breakfast. We can also hypothesize that there are no clinically relevant differences between liquid L-T4 administration 30 min before breakfast or at shorter intervals.

A Double-Blind Placebo-Controlled Trial of Liquid Thyroxine Ingested at Breakfast: Results of the TICO Study

BACKGROUND

Levothyroxine (LT4) is the recommended treatment for millions of hypothyroid patients. Current guidelines recommend that LT4 tablets be taken in a fasting state, but inability to adhere to this often leads to poor therapy compliance.

METHODS

A randomized, double-blind, placebo-controlled, crossover trial was conducted in previously untreated hypothyroid patients randomly assigned to receive an oral solution of LT4 either at least 30 minutes before breakfast or directly at breakfast time. Each patient completed two six-week treatment periods, with different timing of active LT4 administration: placebo before breakfast and active LT4 at breakfast, or vice versa. At the end of each period, thyrotropin (TSH), free thyroxine (fT4), and free triiodothyronine (fT3) were measured. The primary endpoint was to verify any difference in serum TSH levels whether consuming liquid LT4 at breakfast or 30 minutes prior to breakfast.

RESULTS

A total of 77 patients (64 females; median age 45.4 ± 3.7 years) completed the study. No statistically significant differences in serum TSH, fT4, or fT3 levels were observed whether LT4 was taken at breakfast or 30 minutes before, in a fasting state. No significant effect from the sequence of regimens, breakfast composition, and/or concomitantly administered drugs was observed on the dose of LT4 administered, or on the post-treatment serum TSH values.

CONCLUSIONS

The TICO study suggests that a liquid LT4 formulation can be ingested directly at breakfast, thus potentially improving therapeutic compliance. This observation is of considerable clinical relevance, since non-adherence to LT4 therapy requirements is more likely to cause variability in serum TSH concentrations.

Thyroid Hormone Profile in Patients Ingesting Soft Gel Capsule or Liquid Levothyroxine Formulations with Breakfast

Background. Recently, it has been shown that liquid L-T4 formulation can be ingested with breakfast. This study looked to extend these findings by investigating whether a soft gel capsule formulation of L-T4 could also be ingested at breakfast time. Methods. 60 patients (18-65 yrs), previously submitted to thyroidectomy for proven benign goitre in stable euthyroidism receiving liquid L-T4 therapy ingested with breakfast, were enrolled. TSH, fT4, and fT3 levels were assessed in all the patients who were switched from liquid L-T4 to a soft gel capsule formulation at the same dosage of L-T4. After 6 months, TSH, fT4, and fT3 levels were determined again. Results. There were no differences in TSH levels, but fT3 and fT4 levels during treatment with the soft gel capsule were significantly lower than those at enrolment with the liquid L-T4 formulation (TSH median (min-max): 1.9 (0.5-4.0) versus 2.2 (0.5-4.5) mIU/L, fT3: 2.5 (2.4-3.1) versus 2.7 (2.4-3.3) pg/mL, p < 0.05, and fT4: 9.9 (8.0-13) versus 10.6 (8.6-13.8) pg/mL, p < 0.0001). Conclusion. Both liquid and soft gel formulations of L-T4 can be taken with breakfast. However, liquid L-T4 would be the preferred formulation for patients in whom even small changes in fT4 and fT3 levels are to be avoided.

Levothyroxine liquid solution versus tablet form for replacement treatment in pregnant women

OBJECTIVE

To evaluate the need and the magnitude of levothyroxine (LT4) increase in hypothyroid pregnant women on liquid compared to tablet formulations.

METHODS

Patients were recruited by searching our "thyroid patients" database. The selection criteria were as follows: a) pregnant women on treatment for hypothyroidism (both liquid and tablet LT4) who gave birth at our hospital between February 2012 and January 2014; b) thyroid stimulating hormone (TSH) and free thyroxine (FT4) levels obtained at least 3 months before missed menstrual cycle, with a TSH value less than 2.5 mIU/L and c) TSH and FT4 obtained within 12 weeks of pregnancy, and each month subsequently.

RESULTS

During pregnancy, 8/31 (25.5%) of the women had to increase the dosage of LT4. Of these, 7/17 (41.2%) were on LT4 replacement therapy with tablets, and 1/14 (7.1%) with liquid formulation (p = 0.038). Daily LT4 was significantly increased in the liquid group only (52.9 ± 19.5 versus 67.5 ± 19.2 mcg/day (p = 0.013). A logistic regression analysis showed that the treatment with LT4 tablets was the only predictor of LT4 increase (OR: 0.44; 95% CI: 0.04-0.83; p = 0.031).

CONCLUSION

Pregnant women on optimal replacement therapy before pregnancy require an increase of LT4 dosage more often when on a tablet than liquid formulation.

Guidelines for the treatment of hypothyroidism: prepared by the american thyroid association task force on thyroid hormone replacement

BACKGROUND

A number of recent advances in our understanding of thyroid physiology may shed light on why some patients feel unwell while taking levothyroxine monotherapy. The purpose of this task force was to review the goals of levothyroxine therapy, the optimal prescription of conventional levothyroxine therapy, the sources of dissatisfaction with levothyroxine therapy, the evidence on treatment alternatives, and the relevant knowledge gaps. We wished to determine whether there are sufficient new data generated by well-designed studies to provide reason to pursue such therapies and change the current standard of care. This document is intended to inform clinical decision-making on thyroid hormone replacement therapy; it is not a replacement for individualized clinical judgment.

METHODS

Task force members identified 24 questions relevant to the treatment of hypothyroidism. The clinical literature relating to each question was then reviewed. Clinical reviews were supplemented, when relevant, with related mechanistic and bench research literature reviews, performed by our team of translational scientists. Ethics reviews were provided, when relevant, by a bioethicist. The responses to questions were formatted, when possible, in the form of a formal clinical recommendation statement. When responses were not suitable for a formal clinical recommendation, a summary response statement without a formal clinical recommendation was developed. For clinical recommendations, the supporting evidence was appraised, and the strength of each clinical recommendation was assessed, using the American College of Physicians system. The final document was organized so that each topic is introduced with a question, followed by a formal clinical recommendation. Stakeholder input was received at a national meeting, with some subsequent refinement of the clinical questions addressed in the document. Consensus was achieved for all recommendations by the task force.

RESULTS

We reviewed the following therapeutic categories: (i) levothyroxine therapy, (ii) non-levothyroxine-based thyroid hormone therapies, and (iii) use of thyroid hormone analogs. The second category included thyroid extracts, synthetic combination therapy, triiodothyronine therapy, and compounded thyroid hormones.

CONCLUSIONS

We concluded that levothyroxine should remain the standard of care for treating hypothyroidism. We found no consistently strong evidence for the superiority of alternative preparations (e.g., levothyroxine-liothyronine combination therapy, or thyroid extract therapy, or others) over monotherapy with levothyroxine, in improving health outcomes. Some examples of future research needs include the development of superior biomarkers of euthyroidism to supplement thyrotropin measurements, mechanistic research on serum triiodothyronine levels (including effects of age and disease status, relationship with tissue concentrations, as well as potential therapeutic targeting), and long-term outcome clinical trials testing combination therapy or thyroid extracts (including subgroup effects). Additional research is also needed to develop thyroid hormone analogs with a favorable benefit to risk profile.

The administration of L-thyroxine as soft gel capsule or liquid solution

INTRODUCTION

Levothyroxine (l-T4) is the mainstay of treating hypothyroidism. The tablet is the traditional formulation of l-T4. Tablet l-T4 malabsorption results from either hindered gastric dissolution of the tablet or binding of l-T4 by sequestrants in the intestinal lumen.

AREAS COVERED

This review provides an overview of the pharmacokinetics of l-T4 formulations available in the market: the tablet, the soft gel capsule and the oral solution. We review literature on the new formulations and anticipate the areas of future research.

EXPERT OPINION

Failure of l-T4 treatment to reach target serum thyroid-stimulating hormone levels generally prompts the physicians to increase l-T4 daily dose. In vitro studies have shown that the soft gel capsule releases the active ingredient more consistently at varying pH than the tablet. In addition, in vivo studies have confirmed the in vitro data and have demonstrated that both the soft gel capsule and the liquid formulation are capable to solve tablet l-T4 malabsorption caused by certain drugs, bariatric surgery or coffee. These new formulations may be attractive also for patients who cannot/do not want to change their (improper) habits of l-T4 ingestion. Finally, the oral solution l-T4 could be suitable for patients who cannot swallow the solid formulations.

Comparison between liquid and tablet levothyroxine formulations in patients treated through enteral feeding tube

BACKGROUND

The majority of clinicians suggest that enteral feedings should be held 1-2 h prior to and after L-T4 administration despite lack of data for continuous enteral nutrition.

AIM

The aim of this study was to: (1) compare the thyroid hormonal profile in patients submitted to L-T4 treatment in tablets or liquid formulation with an enteral feeding tube; (2) evaluate the nursing compliance with the two different formulations.

SUBJECTS AND METHODS

20 euthyroid patients submitted to total laryngectomy and thyroidectomy consecutively started L-T4 treatment in tablets (Group T) or in liquid formulation (Group L) with enteral feeding tube the day after surgery. Tablets were crushed before administration and enteral feeding was stopped for 30 min before and after L-T4 treatment, whereas liquid formulation was placed into the nasoenteric tube immediately. A questionnaire about the preparation and administration of thyroxine replacement therapy was given to the nurses.

RESULTS

No difference of TSH, fT4 and fT3 before and after L-T4 treatment was observed among patients of Group L. A slightly serum TSH increase was observed in Group T, but not reaching statistical significance (2.50 ± 1.18 vs 2.94 ± 1.22 mUI/L), whereas no difference in fT4 and fT3 levels was found. Preparation and administration of liquid L-T4 was considered excellent by 12/13 nurses, whereas tablet formulation was considered poor by 10/13.

CONCLUSIONS

Our data showed that liquid L-T4 formulation can be administered directly through feeding tube with no need for an empty stomach, with a significant improvement in therapy preparation and administration by nurses.

Oral liquid formulation of levothyroxine is stable in breakfast beverages and may improve thyroid patient compliance

Patients on treatment with levothyroxine (T4) are informed to take this drug in the morning, at least 30 min before having breakfast. A significant decrease of T4 absorption was reported, in fact, when T4 solid formulations are taken with food or coffee. According to preliminary clinical study reports, administration of T4 oral solution appears to be less sensitive to the effect of breakfast beverages on oral bioavailability. In the present study, stability of T4 oral solution added to breakfast beverages was investigated. A 1 mL ampoule of single-dose Tirosint® oral solution (IBSA Farmaceutici Italia, Lodi, Italy) was poured into defined volumes of milk, tea, coffee, and coffee with milk warmed at 50 °C, as well as in orange juice at room temperature. Samples were sequentially collected up to 20 min and analyzed by validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods. The results of the study demonstrated that T4 is stable in all beverages after 20 min incubation. Demonstration of T4 stability is a prerequisite for a thorough evaluation of the effect of breakfast beverages on the bioavailability of T4 given as oral solution and for a better understanding of the reasons underlying a decreased T4 bioavailability administered as solid formulations.