The difficult patient: drug interaction and the influence of concomitant diseases on the treatment of hypothyroidism

Adherence to thyroid therapy and depressive status among patients with hypothyroidism in the northern of Jordan: A cross-sectional study

Hypothyroidism is a chronic and progressive medical condition that requires extreme adherence to medication in order to effectively manage the disease. The aim of this study was to examine patients' adherence to their thyroid therapy and their depressive status and their associated predictors. This is a cross-sectional study that was conducted between April and June 2023 using a sample of chronic hypothyroidism patients visiting the Jordan University of Science and Technology Health Center in Irbid, along with the Family Medicine and Endocrine clinic at King Abdullah University Hospital. The 8-item Morisky Medication Adherence Scale (MMAS-8) and Patient Health Questionnaire (PHQ)-2 were used to examine patients' adherence level and mental status. A total of 296 patients were involved in this study. Around 35.5% of the patients found to have high level of adherence. Around 27.4% of the patients demonstrated a low level of adherence. The mean PHQ-2 score for the study sample was 2.00 (SD: 1.7) out of 6. Using a cutoff point of 3, we identified that 29.7% of the patients are at risk of developing major depressive disorder. Patients aged 31 to 50 years and married patients were identified to have higher adherence level compared to other patients (P < .05). This study observed a notable low to moderate level of adherence among patients diagnosed with hypothyroidism in Jordan with regards to their prescribed therapeutic regimen. Furthermore, a significant part of the individuals had a susceptibility to the development of major depressive disorder.

An Overview on Different L-Thyroxine (l-T4) Formulations and Factors Potentially Influencing the Treatment of Congenital Hypothyroidism During the First 3 Years of Life

Congenital hypothyroidism (CH) is a relatively frequent congenital endocrine disorder, caused by defective production of thyroid hormones (THs) at birth. Because THs are essential for the development of normal neuronal networks, CH is also a common preventable cause of irreversible intellectual disability (ID) in children. Prolonged hypothyroidism, particularly during the THs-dependent processes of brain development in the first years of life, due to delays in diagnosis, inadequate timing and dosing of levothyroxine (l-thyroxine or l-T₄), the non-compliance of families, incorrect follow-up and the interference of foods, drugs and medications affecting the absorption of l-T₄, may be responsible for more severe ID. In this review we evaluate the main factors influencing levels of THs and the absorption of l-T₄ in order to provide a practical guide, based on the existing literature, to allow optimal follow-up for these patients.

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.

Physiological Role and Use of Thyroid Hormone Metabolites - Potential Utility in COVID-19 Patients

Thyroxine and triiodothyronine (T3) are classical thyroid hormones and with relatively well-understood actions. In contrast, the physiological role of thyroid hormone metabolites, also circulating in the blood, is less well characterized. These molecules, namely, reverse triiodothyronine, 3,5-diiodothyronine, 3-iodothyronamine, tetraiodoacetic acid and triiodoacetic acid, mediate both agonistic (thyromimetic) and antagonistic actions additional to the effects of the classical thyroid hormones. Here, we provide an overview of the main factors influencing thyroid hormone action, and then go on to describe the main effects of the metabolites and their potential use in medicine. One section addresses thyroid hormone levels in corona virus disease 19 (COVID-19). It appears that i) the more potently-acting molecules T3 and triiodoacetic acid have shorter half-lives than the less potent antagonists 3-iodothyronamine and tetraiodoacetic acid; ii) reverse T3 and 3,5-diiodothyronine may serve as indicators for metabolic dysregulation and disease, and iii) Nanotetrac may be a promising candidate for treating cancer, and resmetirom and VK2809 for steatohepatitis. Further, the use of L-T3 in the treatment of severely ill COVID-19 patients is critically discussed.

L-T4 Therapy in the Presence of Pharmacological Interferents

Pharmacological interference on L-thyroxine (L-T4) therapy can be exerted at several levels, namely from the hypothalamus/pituitary through the intestine, where the absorption of exogenous L-T4 takes place. A number of medications interfere with L-T4 therapy, some of them also being the cause of hypothyroidism. The clinician should be aware that some medications simply affect thyroid function tests with no need of modifying the dose of L-T4 that the patient was taking prior to their prescription. Usually, the topic of pharmacological interference on L-T4 therapy addresses the patient with primary hypothyroidism, in whom periodic measurement of serum thyrotropin (TSH) is the biochemical target. However, this minireview also addresses the patient with central hypothyroidism, in whom the biochemical target is serum free thyroxine (FT4). This minireview also addresses two additional topics. One is the costs associated with frequent monitoring of the biochemical target when L-T4 is taken simultaneously with the interfering drug. The second topic is the issue of metabolic/cardiovascular complications associated with undertreated hypothyroidism.

Effect of l-thyroxine administration before breakfast vs at bedtime on hypothyroidism: A meta-analysis

PURPOSE

To compare the effects of l-thyroxine (L-T4) administration before breakfast and administration at bedtime on hypothyroidism.

METHODS

The PubMed, EMBASE, Cochrane Library, Web of Science, China National Knowledge Infrastructure (CNKI) and Wanfang databases were searched to identify relevant articles. All prospective or randomized controlled studies (RCTs) comparing L-T4 administration before breakfast to the administration at bedtime in patients with hypothyroidism were included in the analysis.

RESULTS

Initially, 2884 articles were retrieved from the databases, and 10 articles were included in the quantitative analysis. The effect of L-T4 administration before breakfast compared with administration at bedtime had no statistically significant association with hormone thyrotropin (TSH) (Standardized mean differences [SMD] = 0.09, 95% confidence intervals (CI): -0.12, 0.30; P = .39), or free triiodothyronine (FT3) (SMD=-0.19, 95% CI: -0.53, 0.15; P = .28) in patients with hypothyroidism. However, the result of FT4 level was favourable for L-T4 bedtime administration group (SMD=-0.27, 95% CI: -0.52, -0.02; P = .03).

CONCLUSION

Our meta-analysis revealed that L-T4 administration at bedtime is as effective as administration before breakfast for patients with hypothyroidism. Taking L-T4 at bedtime may be an attractive option for patients with hypothyroidism.

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.

Thyroid hormones, metabolic syndrome and Vitamin D in middle-aged and older euthyroid subjects: a preliminary study

AIM

To explore the relationship between thyroid hormones, Vitamin D (Vit.D) serum concentrations and metabolic syndrome (MetS) in euthyroid subjects.

METHODS

123 community-dwelling subjects were enrolled. According to thyroid-stimulating hormone (TSH) values the sample was divided into: (1) group 1 (TSH ≤ 2 mU/L); (2) group 2 (TSH > 2 mU/L).

RESULTS

Group 2 showed higher percentage of subjects with MetS (p = 0.003) and hypertension (p = 0.031), higher values of waist circumference (WC) (p = 0.007), parathyroid hormone (p = 0.016), glycaemia (p = 0.045), triglycerides (p = 0.034) and free T4 (fT4) (p = 0.013). Correlation analysis showed several weak significant correlations: MetS with TSH (r = 0.202, p = 0.031) and fT3 (r = - 0.206, p = 0.028); THS with body mass index (r = 0.187, p = 0.047) and hypertension (r = 0.199, p = 0.034); Vit.D with WC (r = - 0.185, p = 0.04).

CONCLUSIONS

Our results showed a possible association between thyroid hormones and MetS. Visceral fat and insulin resistance may be an interesting link between Vit.D and TSH levels.

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.

Diagnosis and Management of Hypothyroidism: Addressing the Knowledge-Action Gaps

Hypothyroidism presents a large epidemiological burden in India. As a result of subtle and nonspecific clinical symptoms and signs, the condition often goes undiagnosed and is not adequately treated when it is detected. There is heterogeneity in the diagnostic and treatment approaches to hypothyroidism. As a result of the physiological changes in thyroid hormones with age and illness, it is important to tailor the diagnosis and management of this condition in specific populations including pregnant women, infants, children, geriatric patients, and those with comorbid conditions. Enhanced understanding and education of physicians and patients can help to improve the outcomes of treatment in hypothyroidism which should be focused on patient-centered care. Policies and reforms should be crafted and implemented at the national level to curb public health challenges of hypothyroidism. This publication summarizes the recommendations of a national advisory board meeting to identify and bridge the gaps in understanding of the diagnosis and treatment of hypothyroidism in India. As a complement to clinical judgment, these recommendations will foster the diagnosis and management of hypothyroidism in the community and clinics for the benefit of the patients.

FUNDING

Merck Ltd, India.

Phosphate binders as a cause of hypothyroidism in dialysis patients: practical indications from a review of the literature

BACKGROUND

Although fatigue is common in dialysis patients, polypharmacy is seldom listed among its causes. In this report, we describe a dialysis patient who developed severe fatigue due to pharmacological interaction between two commonly prescribed drugs, phosphate binders and levothyroxine.

CASE PRESENTATION

A 65-year old woman, on dialysis for 17 years, complained of fatigue (weight 54 Kg, height 1.55 m, BMI: 23 Kg/m2; malnutrition inflammation index: 10; Charlson index 9). She had been treated with lithium for about 20 years. A heavy smoker, she was obese and diabetic when young, but stopped treatment after weight loss. She had undergone thyroidectomy for papillary carcinoma, left hemicolectomy for colon adenocarcinoma, left quadrantectomy followed by radiotherapy for ductal mammary adenocarcinoma, subtotal parathyroidectomy for tertiary hyperparathyroidism. At the time of this report, she was on thrice-weekly hemodiafiltration (Daugirdas 2 Kt/V: 1.6-1.8). Her recent treatment included spironolactone, amlodipine, perindopril, valproate, lamotrigine, levothyroxine, vitamin D, calcium carbonate, sodium polystyrene and sevelamer. After she questioned her doctor about whether her fatigue might be the result of a drug interaction, levothyroxine interference was identified (TSH, previously normal, increased to 13.07 mU/L, after increasing sevelamer dose, and normalized after change of drug schedule).

LITERATURE REVIEW

only 5 relevant papers on levothyroxine and phosphate binders on dialysis were found on Pubmed and EMBASE (out of 351 titles retrieved). Information was therefore inferred from studies in normal volunteers or in other diseases.

DISCUSSION AND CONCLUSIONS

Our case differs from other reports on lower TSH at diagnosis, underlining the need for awareness of the importance of early diagnosis. Integrating the scant literature on dialysis patients with data available in the general population, some working conclusions can be reached: while all phosphate binders potentially interfere with levothyroxine absorption, interference seems to be highest for sevelamer; interference is limited but not excluded by increasing the intervals between drugs; morning fast is usually indicated but, when clashing with the timing of other drugs, a bedtime dose and liquid preparations may be indicated. In the absence of an agreed control schedule, our case supports close monitoring of TSH (1-3 months if unstable, twice-yearly in stable patients).

MANAGEMENT OF ENDOCRINE DISEASE: Pitfalls on the replacement therapy for primary and central hypothyroidism in adults

Hypothyroidism is one of the most common hormone deficiencies in adults. Most of the cases, particularly those of overt hypothyroidism, are easily diagnosed and managed, with excellent outcomes if treated adequately. However, minor alterations of thyroid function determine nonspecific manifestations. Primary hypothyroidism due to chronic autoimmune thyroiditis is largely the most common cause of thyroid hormone deficiency. Central hypothyroidism is a rare and heterogeneous disorder characterized by decreased thyroid hormone secretion by an otherwise normal thyroid gland, due to lack of TSH. The standard treatment of primary and central hypothyroidism is hormone replacement therapy with levothyroxine sodium (LT4). Treatment guidelines of hypothyroidism recommend monotherapy with LT4 due to its efficacy, long-term experience, favorable side effect profile, ease of administration, good intestinal absorption, long serum half-life and low cost. Despite being easily treatable with a daily dose of LT4, many patients remain hypothyroid due to malabsorption syndromes, autoimmune gastritis, pancreatic and liver disorders, drug interactions, polymorphisms in DIO2 (iodothyronine deiodinase 2), high fiber diet, and more frequently, non-compliance to LT4 therapy. Compliance to levothyroxine treatment in hypothyroidism is compromised by daily and fasting schedule. Many adult patients remain hypothyroid due to all the above mentioned and many attempts to improve levothyroxine therapy compliance and absorption have been made.

Is Parenteral Levothyroxine Therapy Safe in Intractable Hypothyroidism?

CASE

A 32-year old woman was admitted to the hospital due to intractable hypothyroidism refractory to high dose of oral l-thyroxine therapy. She underwent total thyroidectomy and radioactive iodine therapy due to papillary thyroid cancer. After excluding poor adherence to therapy and malabsorption, levothyroxine absorption test was performed. No response was detected. Transient neurologic symptoms developed during the test. She developed 3 attacks consisting of neurologic symptoms during high dose administration. The patient was considered a case of isolated l-thyroxine malabsorption. She became euthyroid after intramuscular twice weekly l-thyroxine therapy.

DISCUSSION

There are a few case reports regarding isolated l-thyroxine. We report successful long term results of twice weekly administered intramuscular l-thyroxine therapy. We also draw attention to neurologic side effects of high dose l-thyroxine therapy.

Diagnosis and management of treatment-refractory hypothyroidism: an expert consensus report

There is a frequently encountered subset of hypothyroid patients who are refractory to standard thyroid hormone replacement treatment and require unexpectedly high doses of levothyroxine. In addition to clinical situations where hypothyroid patients are non-compliant, or where there is the possibility of excipient-induced disease exacerbation (gluten/celiac disease), therapeutic failure may be due to impaired absorption of the administered drug. The common approach to managing patients with unusual thyroxine needs is to escalate the dose of levothyroxine until targeted TSH levels are achieved. This approach can increase the risk for prolonged exposure to supratherapeutic doses of levothyroxine, which increase the chances of adverse outcomes. Repeated adjustments of levothyroxine can also escalate the costs of treatment, as frequent office visits and laboratory tests are required to determine and maintain the desired dose. Clinicians should take a systematic approach to managing patients whom they suspect of having treatment-refractory hypothyroidism. This may include searching for, and adjusting, occult medical conditions and/or other factors that may affect the absorption of levothyroxine, before up-titrating the dose of traditional levothyroxine therapy. Depending on the underlying pathology, another approach that may be considered is to try alternative formulations of levothyroxine that are less susceptible to intolerance issues related to excipients, or, in some cases, to malabsorption. The early discovery of these factors via a thoughtful patient work-up may avoid unnecessary thyroid medication adjustments and their consequences for both patients and clinicians.

A cooperation project between hospital pharmacists and general practitioners about drug interactions in clinical practice

Objectives

(1) To evaluate drug-drug interactions (DDIs) in general practitioners' (GPs) prescriptions; (2) to implement a cooperation project between pharmacists and GPs to improve DDI management and patient care.

Methods

In 2013, pharmacists from the Community Drug Assistance ASL TO1 launched a cooperation project involving 48 GPs. As a first step, GPs were asked to select, from a list, drug associations for which they recommended analysis of occurrence in their prescriptions. The pharmacists (1) analysed GPs' prescriptions dated 2012-2014, according to the list of DDIs selected (n= 9); (2) evaluated solutions for DDI management, using the Micromedex DDI checker database and literature analysis; they then (3) disseminated DDI-related information to GPs through training meetings and (4) assessed the efficacy of these actions through a questionnaire submitted to the GPs in 2013.

Results

(1) Prescriptions analysis: a reduction in the number of DDIs was observed (-14% in 2013 vs 2012, -9% in 2014 vs 2012); in some cases these reductions were statistically significant (calcium carbonate + proton pump inhibitors (PPIs) -50%, p<0.0041, amoxicillin+lansoprazole -42%, p<0.0088). (2) Questionnaire: this was completed by 75% of GPs. The literature analysis was considered interesting by 94% of GPs; solutions were adopted by 89% of GPs and 34% of GPs affirmed that clinical improvements after application of the measures were observed in their patients, even if they could not provide quantitative data for this outcome.

Conclusion

The cooperation project between pharmacists and GPs was effective because it established a professional exchange between the two health professionals. The pharmacist gave support to GPs, which benefited the patients, who gained clinical improvements and improved satisfaction with their medical care, as declared by the GPs in answers to the questionnaire.

[Once weekly L-thyroxine treatment in non-compliance: A case report]

INTRODUCTION

The non-adherence to substitutive treatment by L-thyroxine is the main cause of the discordance between high thyrotropin values and high doses of the drug.

OBSERVATION

In a 36-year-old patient with post-surgery hypothyroidism, thyrotropin values ranged between 100 and 400 mUI/L, although daily replacement therapy included 300 μg of L-thyroxine and 75 μg of L-triiodothyronine. The oral loading test with L-thyroxine was normal and thyrotropin serum level returned to normal values under weekly oral administration of 1000 μg L-thyroxine.

CONCLUSION

The strategy of non-adherence treatment in hypothyroidism is well defined with oral testing of L-thyroxine, followed by oral or parenteral weekly administration of the drug. The L-thyroxine oral test is the gold standard for diagnosis after eliminating of the other conventional causes: drug interactions or digestive malabsorption. L-thyroxine treatment should be discussed on a case-by-case basis, either daily under surveillance or once weekly oral or parenteral high dose.

Retrospective Study of Patients Switched from Tablet Formulations to a Gel Cap Formulation of Levothyroxine: Results of the CONTROL Switch Study

INTRODUCTION

Medication changes involving levothyroxine-either dose titrations or switching formulations-occur frequently in patients with erratic thyroid-stimulating hormone (TSH) levels and persistent hypothyroid symptoms. We investigated whether switching patients from levothyroxine tablets to a gel cap formulation of levothyroxine might reduce dose adjustments and improve tolerability and efficacy outcomes.

OBJECTIVES

Primary study objectives included quantifying the percentage of patients achieving TSH levels within a pre-specified range, median dose changes experienced, and the percentage of patients with improved hypothyroid symptom control after switching from levothyroxine tablets to levothyroxine gel caps.

METHODS

A retrospective medical chart review was conducted among 99 randomly selected hypothyroid patients who were switched from a tablet to a gel cap formulation of levothyroxine. Patients were required to have been on levothyroxine monotherapy for ≥1 year prior to the medication switch. Data was collected for 6 months pre-switch and up to 6 months post-switch.

RESULTS

Of the 99 patients studied, the majority (51.5%) experienced no documented change in TSH status after the switch (P < 0.0001). However, there was a decrease in the mean number of dose changes experienced (1.61 ± 0.96 vs. 0.73 ± 0.96; P < 0.0001). Improved hypothyroid symptom control was reported among 61.6% of patients (61 of 99; P < 0.0001).

CONCLUSION

The results of CONTROL Switch support a strategy of switching patients who may experience tolerability or efficacy problems with standard levothyroxine tablets to the levothyroxine gel cap formulation.

The Economic Impact of Levothyroxine Dose Adjustments: the CONTROL HE Study

Background

In general, hypothyroidism can be adequately treated with a consistent daily dose of levothyroxine. However, the need for levothyroxine dose adjustments is frequent in clinical practice. The extent to which levothyroxine dose adjustments increase the utilization of healthcare resources has not previously been described in the clinical literature.

Objective

The primary objective of our study was to measure the effect of levothyroxine dose adjustments in terms of their utilization of healthcare resources including direct and indirect costs. A secondary goal was to identify any differences in patient characteristics that may be responsible for levothyroxine dose adjustments.

Methods

A retrospective medical chart review was conducted among patients of selected healthcare providers in the USA. Patients who were recently started on levothyroxine therapy (<6 months) were excluded to avoid situations that were more likely attributable to treatment initiation than inadequate therapeutic effect. Trained nurses extracted data from patient charts and electronic medical record systems for review. We analyzed the cost of resources consumed by the frequency of levothyroxine dose changes over 24 months: 0 dose changes (no dose adjustment group); one dose change, two dose changes, three or more dose changes (≥1 dose adjustment group).

Results

The study included 454 patients. Overall estimated resource utilization was higher per patient in the ≥1 dose adjustment group (US$5824) vs. the no dose adjustment group (US$3166) during the 24-month study period. When direct and indirect costs were combined, overall costs of care were greatest in patients requiring three or more dose adjustments (US$8220/patient). Patients in this cohort incurred 2.5-fold greater total costs compared with patients requiring no dose adjustments (US$8220 vs. US$3166). Among the 58 patients in the group requiring three or more dose adjustments, mean direct medical costs were significantly higher than in the patients requiring no dose adjustments (US$6387 vs. US$2182). Patients with at least one dose adjustment experienced a 40.3% increase in lost productivity vs. patients who had no dose adjustments (US$1381 vs. US$984). Loss of productivity was highest among patients with three or more levothyroxine dose adjustments. Among this cohort, there was an 86.4% increase in lost productivity vs. patients who had no levothyroxine dose adjustments (US$1833 vs. US$984).

Conclusions

Patients experiencing multiple levothyroxine dose adjustments were shown to consume more healthcare resources, resulting in higher costs than those who required no dose adjustments. Each care episode contributed to lost time and wages with total estimated lost productivity escalating with increasing levothyroxine dose adjustments over a 24-month period.

Electronic supplementary material

The online version of this article (doi:10.1007/s40261-016-0462-3) contains supplementary material, which is available to authorized users.

Factors Affecting Gastrointestinal Absorption of Levothyroxine: A Review

PURPOSE

Levothyroxine (LT4) is a drug with a narrow therapeutic index, applied in small amounts (micrograms), which makes interactions in the absorption phase clinically significant. The main aim of this article was to review and present the latest information on factors that affect the gastrointestinal absorption of this drug.

METHODS

Relevant data were collected by using the MEDLINE, PubMed, EMBASE, Web of Science, Science Direct, and Scopus databases with the key words levothyroxine and absorption. Searches were not limited to specific publication types, study designs, dates, or languages. The reports were highly variable in the amount of information provided regarding study design and methods. Because of the heterogeneity of studies, no statistical analysis was performed.

FINDINGS

Many gastrointestinal disorders, such as celiac disease, atrophic gastritis, lactose intolerance, and Helicobacter pylori infection, may impede the absorption of levothyroxine. During treatment of these disorders, it is necessary to monitor serum thyroid-stimulating hormone and free T4 values to reduce the risk of developing iatrogenic hyperthyroidism. Soybeans and coffee have the greatest impact on the reduction of absorption, whereas vitamin C has the ability to increase it. Conversely, the effect of dietary fiber on the absorption of LT4 is not yet fully understood; further research is needed on this topic. A decrease in the absorption of LT4 is established and clinically significant when administered concomitantly with cholestyramine, colesevelam, lanthanum, calcium carbonate, calcium citrate, calcium acetate, iron sulfate, ciprofloxacin, aluminum hydroxide, sevelamer, or proton pump inhibitors. This effect should be taken into consideration when prescribing these drugs concomitantly with LT4. The effects of Giardia lamblia infection and the influence of orlistat, polystyrene sulfonate, raloxifene, and simethicone on absorption of LT4 have been poorly documented. For bariatric surgery, sucralfate and H₂-antagonist interactions are not well founded or contradictory evidence is available regarding their existence; additional research should be conducted.

IMPLICATIONS

The majority of the interactions are clinically significant. They are based on the LT4 adsorption on interfering substances in the digestive tract, as well as a consequently reduced amount of the drug available for absorption. These interactions can be avoided by separating the administration of LT4 and the interfering substance.

Out-of-Reference Range Thyroid-Stimulating Hormone Levels in Levothyroxine-Treated Primary Hypothyroid Patients: A Multicenter Observational Study

OBJECTIVE

Although levothyroxine (LT4) replacement therapy for hypothyroidism has been established as safe, inexpensive and effective, many studies from different countries reported out-of-reference range thyroid-stimulating hormone (TSH) values for the hypothyroid patients under LT4 treatment. The aim of this study was to determine TSH levels of primary hypothyroid patients under LT4 treatment and to assess self-reported compliance with daily LT4 intake in tertiary care centers in Turkey.

DESIGN

In this cross-sectional, observational study, adult patients with primary hypothyroidism, receiving LT4 treatment for at least 6 months, were included. The patients were from 12 tertiary care centers in 9 cities of Turkey. TSH and free T4 levels were recorded from patient files and self-reported compliance with daily LT4 intake was assessed by interviewing the subjects at the last visit.

RESULTS

A total of 1,755 subjects (46 ± 13 years; F/M: 89.9/10.1%) with primary hypothyroidism were enrolled. Of the hypothyroid subjects, 44.8% had out-of-reference range serum TSH levels. TSH values were over the reference range (TSH > 4 mIU/L) in 26.2% and were under the reference range (TSH < 0.5 mIU/L) in 18.6% of the patients. Total duration of LT4 treatment was 5.9 ± 4.7 years and mean dose was 1.2 ± 0.6 μg/kg/day. Non-compliant patients (31.1%) had higher TSH levels (6.9 ± 16 vs 3.8 ± 0.9 mIU/L, P = 0.01) compared to compliant patients.

CONCLUSION

The results of this study revealed that nearly half of the hypothyroid patients had out-of-reference range serum TSH values, despite under LT4 treatment. Compliance with LT4 treatment seems to be one of the major determinants to reach the target TSH levels in hypothyroid patients.

Comorbidities, Concomitant Medications, and Diet as Factors Affecting Levothyroxine Therapy: Results of the CONTROL Surveillance Project

Background

The CONTROL Surveillance Project was a comprehensive patient-based survey conducted among hypothyroid patients undergoing treatment. The primary objective of the study was to specifically quantify the prevalence of factors adversely affecting levothyroxine therapy.

Methods

Participants were selected from a large proprietary database. Those eligible for the study completed a 21-question survey.

Results

Of the eligible hypothyroid patients, 925 (92.5 %) were being treated with levothyroxine monotherapy. The mean age was 60.4 years; 755 (81.6 %) were female and 168 (18.2 %) were male. Almost half of those receiving levothyroxine (435, 47.0 %) had at least one comorbid condition that could adversely affect its absorption: gastroesophageal reflux disease (33.8 % of patients), irritable bowel syndrome (9.7 %), lactose intolerance (7.8 %), or a history of gastric bypass surgery or bowel resection (3.0 %). Other factors reported by many patients that could adversely affect levothyroxine absorption included use of prescription medications (20.6 %) and over-the-counter medications (34.3 %) used to treat comorbid gastrointestinal (GI) conditions; use of dietary supplements (51.8 %, primarily calcium and iron); and intake of foods/beverages high in fiber, iodine, or soy (68.0 %). Of the 13.4 % who reported difficulty controlling their hypothyroid symptoms, significantly more patients with comorbid GI conditions reported such difficulty (7.8 versus 5.6 %, P < 0.01). Frequent changes in levothyroxine dosing (two or more dose changes in the past year) were reported by 8.0 % of survey participants. Those with GI comorbidities were nearly twice as likely to have such changes (5.0 versus 3.0 %, P < 0.01).

Conclusion

Better initial workup of patients, including identification of relevant GI comorbidities and allergies, may help in the early detection of factors that may affect the performance of levothyroxine.

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.

Thyroid hormone (levothyroxine) replacement via the respiratory route by inhalation: in vitro exploratory studies

OBJECTIVES

To conduct proof of principle studies that will enable development of noninvasive (respiratory) delivery systems for levothyroxine (T4).

METHODS

Preformulation (solubility, stability), formulation and biopharmaceutical (in vitro absorption, transport, gene expression) studies were conducted. Calu-3 cell line was used for permeation studies.

RESULTS

Solubility profiles of T4 were established in aqueous (PBS, HBSS, isotonic saline) and non-aqueous solvents (PEG 400, PEG 600, propylene glycol, glycerine). Transport of the compound across Calu-3 cells suggested involvement of active transport systems. This correlated with expression of thyroxine transporters (MCT8, MCT10, OATP1A2, LAT1 and LAT2) in the cell line. Diffusion characteristics showed significant absorption with no detection of T4 metabolite (triiodothyronine). Formulation studies revealed that stable formulations could be prepared using a combination of aqueous and non-aqueous solvents.

CONCLUSIONS

Results of the studies indicated that T4 can be absorbed effectively from the respiratory mucosa. Factors affecting stability such as pH and temperature should be taken into account during formulation development of this compound for the respiratory route.

Celiac disease detection in hypothyroid patients requiring elevated thyroid supplementation: A prospective cohort study

BACKGROUND

Celiac disease (CD) is associated with hypothyroidism, but the disease prevalence is not thought to be great enough to warrant testing all hypothyroid patients. We hypothesized that hypothyroid patients with concomitant CD would require elevated doses of levothyroxine, and there is a threshold daily dose, above which, hypothyroid patients should be tested for CD.

METHODS

Hypothyroid patients presenting to the endoscopy or endocrinology clinics at the University of Vermont Medical Center were included. Patients were categorized by whether or not they required ≥125mcg/day of levothyroxine. A serum tissue transglutaminase (tTG) was performed on enrolled patients. Patients with an elevated serum tTG underwent endoscopy with duodenal biopsies. Symptoms were assessed by the Gastrointestinal Symptom Rating Scale.

RESULTS

Overall, 500 patients were enrolled and 29% (144 patients) required ≥125mcg/day of levothyroxine. CD was detected in 9 patients. The prevalence of CD ranged from 1.8% in our entire cohort to 12.5% in patients requiring ≥200mcg/day of levothyroxine. Eight patients with CD (89%) required ≥125mcg/day of levothyroxine. Patients who required ≥125mcg/day of levothyroxine had a significantly increased risk of CD (p<0.001). CD was detected in 5.6% of patients requiring ≥125mcg/day of levothyroxine.

CONCLUSIONS

Hypothyroid patients requiring elevated daily doses of levothyroxine are more likely to have CD. Hypothyroid patients requiring ≥125mcg/day of levothyroxine should undergo serologic testing for CD.

Do Not Forget Nephrotic Syndrome as a Cause of Increased Requirement of Levothyroxine Replacement Therapy

Nephrotic syndrome increases L-thyroxine requirements because of urinary loss of free and protein-bound thyroid hormones. We report 2 hypothyroid patients referred to us because of high serum TSH, even though the L-thyroxine daily dose was maintained at appropriate levels or was increased. The cause of nephrotic syndrome was multiple myeloma in one patient and diabetic glomerulosclerosis in the other patient. As part of the periodic controls for diabetes, urinalysis was requested only in the second patient so that proteinuria could be detected. However, as in the first patient, facial puffiness and body weight increase were initially attributed to hypothyroidism, which was poorly compensated by L-thyroxine therapy. In the first patient, the pitting nature of the pedal edema was missed at the initial examination. An endocrinologist consulted over the phone by the practitioner hypothesized some causes of intestinal malabsorption of L-thyroxine. This diagnosis would have been accepted had the patient continued taking a known sequestrant of L-thyroxine, i.e. calcium carbonate. The diagnostic workup of patients with increasing requirements of L-thyroxine replacement therapy should not be concentrated on the digestive system alone. Careful history taking and physical examination need to be thorough. Endocrinologists should not forget nephrotic syndrome that, in turn, can be secondary to serious diseases.

Hypothyroidism in clinical practice

Background:

Hypothyroidism is the most common endocrine disease that was seen in the clinical practice especially for family physicians.

Methods:

This review article covered the important practical clinical issues for managing overt hypothyroidism, subclinical hypothyroidism and hypothyroidism during pregnancy.

Conclusions:

The clinical issues were addressed by clinical scenario followed by questions and stressed on the important clinical points.

Clinical practice guidelines for the management of hypothyroidism

INTRODUCTION

Hypothyroidism has long been known for its effects on different organ systems, leading to hypometabolism. However, subclinical hypothyroidism, its most prevalent form, has been recently related to cardiovascular risk and also to maternal-fetal complications in pregnant women.

OBJECTIVES

In these clinical practice guidelines, several aspects of this field have been discussed with the clear objectives of helping physicians treat patients with hypothyroidism, and of sharing some of our Latin American-based clinical experience.

MATERIALS AND METHODS

The Latin American Thyroid Society commissioned a Task Force on Hypothyroidism to develop evidence-based clinical guidelines on hypothyroidism. A systematic review of the available literature, focused on the primary databases of MedLine/PubMed and Lilacs/SciELO was performed. Filters to assess methodological quality were applied to select the best quality studies. The strength of recommendation on a scale from A-D was based on the Oxford Centre for Evidence--based Medicine, Levels of Evidence 2009, allowing an unbiased opinion devoid of subjective viewpoints. The areas of interest for the studies comprised diagnosis, screening, treatment and a special section for hypothyroidism in pregnancy.

RESULTS

Several questions based on diagnosis, screening, treatment of hypothyroidism in adult population and specifically in pregnant women were posed. Twenty six recommendations were created based on the answers to these questions. Despite the fact that evidence in some areas of hypothyroidism, such as therapy, is lacking, out of 279 references, 73% were Grade A and B, 8% Grade C and 19% Grade D.

CONCLUSIONS

These evidence-based clinical guidelines on hypothyroidism will provide unified criteria for management of hypothyroidism throughout Latin America. Although most of the studies referred to are from all over the world, the point of view of thyroidologists from Latin America is also given.

When thyroid hormone replacement is ineffective?

PURPOSE OF REVIEW

In this article, we will consider the failure of thyroid hormone replacement therapy to normalize serum thyroid stimulating hormone concentrations. We will review circumstances and causes for failures, discuss pertinent unpublished personal cases of didactical value, and provide practical suggestions for providers encountering patients with similar presentations.

RECENT FINDINGS

Recent data are available on the benefit of novel formulations of levothyroxine therapy on malabsorption.

SUMMARY

Most frequently, reasons for ineffectiveness are noncompliance, inappropriate administration of levothyroxine, gastrointestinal disorders, and drug interactions. The diagnostic work-up should include careful history to elucidate the potential reasons for the ineffective therapy.

Subcutaneous application of levothyroxine as successful treatment option in a patient with malabsorption

Background:

Hypothyroidism can usually be treated effectively by oral levothyroxine supplementation. There are, however, some rare circumstances, when oral levothyroxine application is not sufficient, for example malabsorption, interactions with food or other medications, or various gastrointestinal diseases.

Case Report:

We present a 42 year old woman with refractory and severe symptomatic hypothyroidism after subtotal thyroidectomy in spite of high dose oral levothyroxine supplementation. By stepwise increasing oral levothyroxine dosage up to 2200 micrograms plus 80 micrograms of thyronine, no sufficient substitution could be achieved. After suspicion of enteral malabsorption due to a pathological D-Xylose-test, subcutaneous levothyroxine supplementation was started. Finally, a sustained euthyroid state could be achieved.

Conclusions:

For selected patients who do not respond to oral treatment subcutaneous application of levothyroxine can be a suitable and effective therapy.

CYP2C9 and VKORC1 polymorphisms influence warfarin dose variability in patients on long-term anticoagulation

OBJECTIVES

The main aim of this study was to determine whether CYP2C9 and VKORC1 polymorphisms influence warfarin dose variability during initial dose-finding phase and during maintenance treatment after 360 days.

METHODS

Two hundred and six consecutive patients who were beginning warfarin therapy were selected. They were assessed for general and clinical characteristics; prescribed warfarin dose; response to therapy on days 7-10, 30, 60, 180, and 360; adverse events; and CYP2C9 2, 3, 5, 6, 8, 11, and VKORC1 1639G >A assays.

RESULTS

During the first 30 days of anticoagulation, the relative variability of warfarin dose was significantly associated with CYP2C9*2 and CYP2C9*3 polymorphisms (p = 0.02) and with VKORC1 1639G >A genotypes (p = 0.04). Warfarin variability was also statistically different according to predicted metabolic phenotype and to VKORC1 genotypes after 360 days of treatment, and in the phase between 180 and 360 days (long-term dose variability). Both CYP2C9 and VKORC1 polymorphisms were associated with the international normalized ratio (INR) made between 7 and 10 days/initial dose ratio, adjusted for covariates (p < 0.01 and p = 0.02, respectively). Patients carrying VKORC1 and CYP2C9 variants presented lower required dose (at the end of follow-up of 360 days) compared to patients carrying wild-type genotypes (p = 0.04 and p = 0.03, respectively).

CONCLUSIONS

Genetic information on CYP2C9 and VKORC1 is important both for the initial dose-finding phase and during maintenance treatment with warfarin.

Celiac disease and hypothyroidism

BACKGROUND

Celiac disease is more common in patients with hypothyroidism. Malabsorption of levothyroxine has not been studied in this population. We sought to determine if levothyroxine dosing was influenced by the presence and treatment of celiac disease.

METHODS

This retrospective study was conducted at an academic medical center. Cases had hypothyroidism and celiac disease. Controls had hypothyroidism alone and were selected randomly through the endocrinology clinic records. Celiac disease was defined as representative pathology with positive serology. Age, sex, height, weight, body mass index, creatinine, and medical comorbidity were assessed for cases and controls. The levothyroxine dose and weight-based levothyroxine dose necessary to maintain a euthyroid state was evaluated for controls, and before and after celiac disease therapy for cases.

RESULTS

Celiac disease was identified in 152 patients, and 22 patients had concomitant hypothyroidism (14.5%). Seven cases met inclusion criteria. Overall, 200 control patients were identified. The mean celiac disease pretreatment levothyroxine dose and weight-based levothyroxine dose needed to maintain a euthyroid state were higher in cases than in controls (154 μg vs 106 μg, P=.007, and 2.6 μg/kg vs 1.3 μg/kg, P <.001). Doses decreased significantly after treatment of celiac disease (154 μg vs 111 μg, P=.03; and 2.64 μg/kg vs 1.89 μg/kg, P=.04). All cases required at least 125 μg of levothyroxine initially to maintain a euthyroid state.

CONCLUSIONS

Levothyroxine malabsorption likely occurs with hypothyroidism and untreated celiac disease. Absorption may improve after celiac disease treatment. Screening for celiac disease in patients with hypothyroidism requiring elevated levothyroxine doses warrants further investigation.

Increased levothyroxine requirement in a woman with previously well-controlled hypothyroidism and intestinal giardiasis

The most common cause of apparent inefficiency or resistance to oral therapy with levothyroxine for hypothyroidism is nonadhesion. However, in some subjects in whom the control of hypothyroidism is extremely difficult, levothyroxine bioavailability defects should be considered. We report here the case of a 57-year-old woman with hypothyroidism that was well-controlled for the previous 6 years but suddenly presented with poor hormonal control and abdominal symptoms, despite repeatedly reporting good compliance to therapy. Adequate control of thyroid function was only obtained after intestinal giardiasis was diagnosed and treated.