Optimizing Levothyroxine Dose Adjustment After Thyroidectomy With a Decision Tree.

BACKGROUND: After thyroidectomy, patients require Levothyroxine (LT4). It may take years of dose adjustments to achieve euthyroidism. During this time, patients encounter undesirable symptoms associated with hypo- or hyper-thyroidism. Currently, providers adjust LT4 dose by clinical estimation, and no algorithm exists. The objective of this study was to build a decision tree that could estimate LT4 dose adjustments and reduce the time to euthyroidism. METHODS: We performed a retrospective cohort analysis on 320 patients who underwent total or completion thyroidectomy at our institution. All patients required one or more LT4 dose adjustments from their initial postoperative dose before attaining euthyroidism. Using the Classification and Regression Tree algorithm, we built various decision trees from patient characteristics, estimating the dose adjustment to reach euthyroidism. RESULTS: The most accurate decision tree used thyroid-stimulating hormone values at first dose adjustment (mean absolute error = 13.0 µg). In comparison, the expert provider and naïve system had a mean absolute error of 11.7 µg and 17.2 µg, respectively. In the evaluation dataset, the decision tree correctly predicted the dose adjustment within the smallest LT4 dose increment (12.5 µg) 79 of 106 times (75%, confidence interval = 65%-82%). In comparison, expert provider estimation correctly predicted the dose adjustment 76 of 106 times (72%, confidence interval = 62%-80%). CONCLUSIONS: A decision tree predicts the correct LT4 dose adjustment with an accuracy exceeding that of a completely naïve system and comparable to that of an expert provider. It can assist providers inexperienced with LT4 dose adjustment.

Comparison of Incident Cardiovascular Event Rates Between Generic and Brand l-Thyroxine for the Treatment of Hypothyroidism.

OBJECTIVE: To determine whether levothyroxine (L-T4) preparation (generic vs brand) affected hospitalization for cardiovascular events. PATIENTS AND METHODS: We performed a retrospective analysis using a large administrative claims database, OptumLabs Data Warehouse, creating two 1-to-1 propensity score-matched cohorts initiating generic or brand L-T4. Patients were followed for a mean of 1.0±1.2 years (range, 0-9.3 years). We included 87,902 propensity score-matched patients (43,951 patients per cohort) initiating generic or brand L-T4. Variables included in matching were age, sex, race/ethnicity, residence region, selected comorbidities, and Charlson-Deyo comorbidity score. Patients with previous use of any thyroid preparation, amiodarone, or lithium were excluded. Primary outcomes were the event rates for hospitalizations for incident atrial fibrillation, myocardial infarction, congestive heart failure, or stroke. RESULTS: In the generic L-T4 cohort, 35,242 (80.2%) were women and 7327 (16.7%) were 65 years of age or older; in the brand L-T4 cohort, 34,633 (78.8%) were women and 8092 (18.4%) were 65 years of age or older. We found no differences in event rates (events per 1000 person-years) for 4 outcomes comparing generic and brand L-T4 therapy: (1) atrial fibrillation (1.82 vs 2.19; hazard ratio [HR], 1.22; 95% CI, 0.90-1.65; P=.19); (2) myocardial infarction (2.12 vs 1.83; HR, 0.86; 95% CI, 0.64-1.17; P=.35); (3) congestive heart failure (2.27 vs 2.00; HR, 0.88; 95% CI, 0.66-1.18; P=.41); and (4) stroke (3.10 vs 2.38; HR, 0.77; 95% CI, 0.59-1.00; P=.05). Stratification by age group revealed no differences. CONCLUSION: In patients with newly treated hypothyroidism, cardiovascular event rates were similar for generic and brand L-T4.

Sexual function and depressive symptoms in young women with hypothyroidism receiving levothyroxine/liothyronine combination therapy: a pilot study.

Objective Even mild hypothyroidism in pre-menopausal women is accompanied by impaired sexual functioning. The study was aimed at comparing the effect of levothyroxine, administered alone or in combination with liothyronine, on sexual function and depressive symptoms in pre-menopausal women treated because of hypothyroidism. Methods This quasi-randomized, single-blind study included 39 young women receiving levothyroxine treatment who, despite thyrotropin and thyroid hormone levels within normal limits, still experienced clinical symptoms of hypothyroidism. These patients were divided into two groups: group A (n = 20) continued levothyroxine treatment, while group B (n = 19) received levothyroxine/liothyronine combination therapy. At the beginning of the study, and 6 months later, all participants of the study filled in questionnaires evaluating female sexual functioning (Female Sexual Function Index; FSFI) and the presence and severity of depressive symptoms (Beck Depression Inventory-Second Edition; BDI-II). Results The study was completed by 37 women. Baseline sexual functioning and depressive symptoms did not differ between the study groups. Neither the total FSFI score nor the domain scores changed throughout the study in women who continued levothyroxine treatment. Compared to levothyroxine administered alone, levothyroxine/liothyronine combination therapy increased scores for two domains: sexual desire and arousal, tended to increase the total FSFI score, as well as tended to decrease the overall BDI-II score. The effect of the combination therapy on sexual function correlated with a treatment-induced increase in serum levels of free triiodothyronine and testosterone. Conclusions The obtained results suggest that levothyroxine administered together with liothyronine is superior to levothyroxine administered alone in affecting female sexual functioning.

Effects of Levothyroxine Replacement or Suppressive Therapy on Energy Expenditure and Body Composition.

BACKGROUND: Thyrotropin (TSH)-suppressive doses of levothyroxine (LT4) have adverse effects on bone and cardiac function, but it is unclear whether metabolic function is also affected. The objective of this study was to determine whether women receiving TSH-suppressive LT4 doses have alterations in energy expenditure or body composition. METHODS: This study was a cross-sectional comparison between three groups of women: 26 women receiving chronic TSH-suppressive LT4 doses, 80 women receiving chronic replacement LT4 doses, and 16 untreated euthyroid control women. Subjects underwent measurements of resting energy expenditure (REE), substrate oxidation, and thermic effect of food by indirect calorimetry; physical activity energy expenditure by accelerometer; caloric intake by 24-hour diet recall; and body composition by dual X-ray absorptiometry. RESULTS: REE per kilogram lean body mass in the LT4 euthyroid women was 6% lower than that of the LT4-suppressed group, and 4% lower than that of the healthy control group (p = 0.04). Free triiodothyronine (fT3) levels were directly correlated with REE, and were 10% lower in the LT4 euthyroid women compared with the other two groups (p = 0.007). The groups of subjects did not differ in other measures of energy expenditure, caloric intake, or body composition. CONCLUSIONS: LT4 suppression therapy does not adversely affect energy expenditure or body composition in women. However, LT4 replacement therapy is associated with a lower REE, despite TSH levels within the reference range. This may be due to lower fT3 levels, suggesting relative tissue hypothyroidism may contribute to impaired energy expenditure in LT4 therapy.

[Historical aspects and new formulations of levothyroxine sodium for hypothyroidism treatment].

At the end of the 19th century symptoms and signs of hypothyroidism were described in the medical literature. At that time myxedema was a main clinical presentation of the hypothyroid patient. Today, the diagnosis of hypothyroidism is determined mainly by laboratory evaluation with most patients exhibiting only a few clinical signs of thyroid dysfunction. The treatment of hypothyroidism has progressed from partially purified extracts of bovine thyroid gland to an oral administration of synthetic hormone. Since 1981 the only thyroid hormone replacement drug approved by the Israeli Ministry of Health was the Eltroxin brand, made by GlaxoSmithKline. Levothyroxine has a narrow therapeutic range, thus a potential variance exists in the therapeutic efficacy among different levothyroxine preparations. In 2007 the Food and Drugs Administration (FDA) announced that the difference in potency of various levothyroxine brands should not exceed ten percent. In 2007 the GSK Company moved the manufacturing of Eltroxin from Canada to Germany. This resulted in a change of the inert ingredients of the drug. It is of interest to know that since the arrival of the new thyroxine formulation in the Israeli pharmaceutical market there has been a dramatic increase in reports of adverse reactions. The media coverage of adverse effects associated with Eltroxin became widespread in television, newspapers and internet sites. This led to a burden on the healthcare system, manifesting itself by an increase in thyroid blood tests, physician follow-up visits, as well as the importing and distribution of a new brand of thyroxine.

Thyroxine and triiodothyronine content in commercially available thyroid health supplements.

BACKGROUND: As defined by the Dietary Supplement Health and Education Act 1997, such substances as herbs and dietary supplements fall under general Food and Drug Administration supervision but have not been closely regulated to date. We examined the thyroid hormone content in readily available dietary health supplements marketed for "thyroid support." METHODS: Ten commercially available thyroid dietary supplements were purchased. Thyroid supplements were dissolved in 10 mL of acetonitrile and water with 0.1% trifloroacetic acid and analyzed using high-performance liquid chromatography for the presence of both thyroxine (T4) and triiodothyronine (T3) using levothyroxine and liothyronine as a positive controls and standards. RESULTS: The amount of T4 and T3 was measured separately for each supplement sample. Nine out of 10 supplements revealed a detectable amount of T3 (1.3-25.4 µg/tablet) and 5 of 10 contained T4 (5.77-22.9 µg/tablet). Taken at the recommended dose, 5 supplements delivered T3 quantities of greater than 10 µg/day, and 4 delivered T4 quantities ranging from 8.57 to 91.6 µg/day. CONCLUSIONS: The majority of dietary thyroid supplements studied contained clinically relevant amounts of T4 and T3, some of which exceeded common treatment doses for hypothyroidism. These amounts of thyroid hormone, found in easily accessible dietary supplements, potentially expose patients to the risk of alterations in thyroid levels even to the point of developing iatrogenic thyrotoxicosis. The current study results emphasize the importance of patient and provider education regarding the use of dietary supplements and highlight the need for greater regulation of these products, which hold potential danger to public health.

A population-based assessment of the drug interaction between levothyroxine and warfarin.

Most drug interaction resources suggest that levothyroxine can dramatically potentiate the effect of warfarin. However, the mechanistic basis of the interaction is speculative, and little evidence supports a meaningful drug interaction. We conducted a population-based nested case-control study to examine the risk of hospitalization for hemorrhage following the initiation of levothyroxine in a cohort of 260,076 older patients receiving warfarin. In this group, we identified 10,532 case subjects hospitalized for hemorrhage and 40,595 controls. In the primary analysis, we found no association between hospitalization for hemorrhage during warfarin therapy and initiation of levothyroxine in the preceding 30 days (adjusted odds ratio 1.11, 95% confidence interval 0.67-1.86). Secondary analyses using more remote initiation of levothyroxine also found no association. These findings suggest that concerns about a clinically meaningful levothyroxine-warfarin drug interaction are not justified. Drug interaction resources that presently characterize this interaction as important should reevaluate this classification.

Prevalence of atrial fibrillation in patients taking TSH suppression therapy for management of thyroid cancer.

BACKGROUND: Suppression of thyroid stimulating hormone (TSH) below the normal range with administration of L-thyroxine has been shown to improve survival in patients treated for thyroid cancer (TC). Although most TC patients require long-term TSH suppression therapy, the effect of this treatment on cardiac rhythm remains unknown. A cross-sectional study was conducted to determine the prevalence of atrial fibrillation (AF) in TC patients on TSH suppressive therapy. METHODS: All TC patients seen between June 2009 and March 2010 through a multidisciplinary thyroid oncology clinic, Halifax, Nova Scotia, Canada, for whom TSH suppressive therapy had previously been recommended, were recruited into the study. Each patient underwent an electrocardiogram and filled out a questionnaire relevant to causes, signs/symptoms of AF and/or its complications. The prevalence of AF in this population then was compared against the published prevalence of AF in general populations. RESULTS: A total of 351 patients were seen in the thyroid clinic of which 136 patients met the inclusion criteria for the study. The mean age was 52 years, 85% were female, and mean follow-up duration prior to recruitment was 11 years. The mean TSH was 0.17 mIU/L (Normal: 0.35 - 5.5 mIU/L). There were 14 patients found to have AF (two patients had long-standing persistent AF and 12 patients had paroxysmal AF). The mean ages of patients with and without AF were 61.6 years and 51.4 years, respectively (P = 0.01). Prevalence of AF in the study group was 10.3%; the rate of AF in the TC patients aged 60 years and over (17.5%) was higher than the rate of AF in published data in people 60 years and over (P < 0.001). AF was diagnosed after the initiation of the TSH suppression therapy in all except one patient. CONCLUSION: TSH suppression in thyroid cancer is associated with a high prevalence of AF, particularly in older individuals.

[Levothyroxine and the problem of interchangeability of drugs with narrow therapeutic index]. / Levotiroxina e o problema da permutabilidade de drogas de estreito intervalo terapêutico.

The exchange of a prescribed drug by other similar, by generic products and even by custom products has become common practice in our country, often ignoring basic tenets of bioequivalence, interchangeability, stability and characteristics of the pharmaceutical compounds. In the case of drugs of narrow therapeutic index, such as levothyroxine, these problems are intensified, putting the effectiveness of treatment and patient health at serious risk. We review the pertinent legislation, emphasizing the characteristics of levothyroxine and adverse effects that limit the interchangeability of the compound.

Levotiroxina e o problema da permutabilidade de drogas de estreito intervalo terapêutico / Levothyroxine and the problem of interchangeability of drugs with narrow therapeutic index

Tem se tornado prática comum em nosso país a troca de medicamentos prescritos por outros similares, por produtos genéricos e até mesmo por produtos manipulados, muitas vezes ignorando-se preceitos básicos de bioequivalência, permutabilidade, estabilidade e características específicas do composto farmacêutico. No caso de drogas de índice terapêutico estreito, como a levotiroxina, esses problemas se agravam colocando em sério risco a eficácia do tratamento e a saúde do paciente. Revemos a legislação pertinente ressaltando as características da levotiroxina e os efeitos adversos que limitam a permutabilidade do composto.

The exchange of a prescribed drug by other similar, by generic products and even by custom products has become common practice in our country, often ignoring basic tenets of bioequivalence, interchangeability, stability and characteristics of the pharmaceutical compounds. In the case of drugs of narrow therapeutic index, such as levothyroxine, these problems are intensified, putting the effectiveness of treatment and patient health at serious risk. We review the pertinent legislation, emphasizing the characteristics of levothyroxine and adverse effects that limit the interchangeability of the compound.

Thyroid cancer: possible role of telemedicine.

Telemedicine is extremely useful when distance could hinder diagnostic procedures, disease management, or when severe side-effects may occur in patients not within easy reach of medical care and requiring prompt action and specific therapies. Telemedicine has been successfully adopted in the management of chronic patients, particularly in those with cardiologic or oncologic diseases. In the treatment of differentiated thyroid cancer, requiring long-term check-ups and visits as well as administration of high doses of levothyroxine (TSH - thyroid-stimulating hormone - suppression), also in elderly patients, telemedicine seems particularly indicated. Moreover, these distant monitoring techniques could not only reduce long-term management costs but also considerably decrease cardiovascular risks associated with these patients. The present review aims to provide some general information on telemedicine and its possible fields of action with regard to distant monitoring of patients with differentiated thyroid carcinoma.

Thyroid hormone withdrawal in patients with differentiated thyroid carcinoma: a one hundred thirty-patient pilot survey on consequences of hypothyroidism and a pharmacoeconomic comparison to recombinant thyrotropin administration.

The study objective was to elucidate clinical, quality-of-life, and pharmacoeconomic effects of hypothyroidism secondary to thyroid hormone withdrawal (withdrawal) in athyroid patients with differentiated thyroid cancer (DTC). We also intended to compare societal costs of withdrawal and recombinant human thyroid-stimulating hormone administration (rhTSH) in this population. We mailed a 13-item pilot survey to patients with DTC who had undergone withdrawal before diagnostic whole-body scan (dxWBS). Using survey results and actual and estimated cost data, we retrospectively constructed a societal cost model comparing withdrawal versus rhTSH and performed a sensitivity analysis by increasing the conservatism of 8 assumptions about withdrawal costs. One hundred thirty (55%) of 236 patients answered the questionnaire. Among respondents, 92% had symptomatic and 85% multisymptomatic hypothyroidism. Almost half sought medical attention for hypothyroid complaints. Approximately one third drove motor vehicles while hypothyroid. Median absence from salaried work was 11 days per withdrawal. In the pharmacoeconomic model, societal costs per dxWBS were approximately 326 euro (25%) greater for withdrawal than for rhTSH. In the sensitivity analysis, societal costs of rhTSH exceeded those of withdrawal by approximately 307 euro (30%). In conclusion, hypothyroidism secondary to withdrawal causes important morbidity, safety risks, and productivity impairment. rhTSH avoids these drawbacks at roughly equivalent societal cost to that of withdrawal.

Assessment of levothyroxine sodium bioavailability: recommendations for an improved methodology based on the pooled analysis of eight identically designed trials with 396 drug exposures.

BACKGROUND: Assessment of dosage form performance in delivering endogenous compounds, such as hormones, in vivo requires a specific approach. OBJECTIVES: Assessment of relative bioavailability of levothyroxine sodium (L-T4) from eight solid preparations, compared with a liquid formulation, by using pharmacological doses, and critical evaluation of trial methodology based on the pooled analysis of individual data. DESIGN: Eight open-label, randomised, single-dose, crossover phase I studies using eight solid L-T4 dosage forms (25, 50, 75, 100, 125, 150, 175, 200 microg per tablet; administered total doses 600, 625 or 700 microg) and a liquid formulation; assessment of relative bioavailability by 90% confidence intervals for the relative area under the concentration-time curve (AUC) of total thyroxine (TT4), i.e. protein-bound plus free thyroxine, calculated by using the recommended log AUC four-way analysis of variance models for crossover designs. For the pooled analysis, general linear models were applied to assess the validity of model assumptions, to identify potential sources of effect modification, to discuss alternative modelling approaches with respect to endogenous hormone secretion and to give recommendations for future designs and sample sizes. PARTICIPANTS: One hundred and sixty-nine healthy males; 29 of these individuals participating in two studies. INTERVENTIONS: Single oral doses of L-T4 tablets and the liquid formulation administered after fasting, separated by at least 6 weeks; a total of 396 drug exposures. MAIN OUTCOME MEASURES: TT4 AUC from 0 to 48 hours and peak plasma concentration with and without baseline correction. RESULTS: Each study demonstrated equivalence of the tablets to the drinking solution, independent of the chosen analysis model. Sequence effects that could devalidate the chosen crossover approach were not found. Period effects with changing directions that could best be explained by seasonal variation were detected. While the pre-specified method of baseline correction of simply subtracting individual time-zero TT4 values was disadvantageous, the analysis of total AUC could be improved considerably by covariate adjustment for baseline TT4. With this approach, sample sizes could have been substantially reduced or, alternatively, the recommended equivalence ranges could be reduced to +/-6%. CONCLUSION: Using a single pharmacological dose of L-T4 in two-period crossover designs is a safe and reliable procedure to assess L-T4 dosage form performance. With an adequate statistical modelling approach, the design is efficient and allows general conclusions with moderate sample sizes.

A longitudinal assessment of bone loss in women with levothyroxine-suppressed benign thyroid disease and thyroid cancer.

To determine if differing degrees of levothyroxine (LT4) suppression therapy for benign and malignant thyroid disease are associated with proportionately increased rates of bone loss, this longitudinal assessment of bone densitometry changes (single-photon and dual-photon absorptiometry) was conducted in three groups of subjects: 24 thyroid cancer patients who were treated with near-total thyroidectomy, radioiodine ablation, and aggressive LT4-suppression; 44 patients who were treated with more conservative LT4-suppression for benign thyroid disorders; and 24 normal controls. Bone densitometry values were adjusted for age, weight, height, and menopausal status. The rates of bone loss in benign LT4-suppressed patients were greater than those in controls at the midradius, distal radius, lumbar spine, and femoral neck. The rates of loss in the thyroid cancer patients were also greater than those in the controls at all four sites and greater than in the benign LT4-suppressed patients at the midradius, distal radius, and femoral neck but not in the lumbar spine. Rates of bone loss were not significantly correlated with LT4 dose or with the serum level of T4 or TSH. LT4-suppression therapy for benign thyroid disease is associated with accelerated bone loss. More aggressive LT4-suppression for thyroid cancer is associated with even greater bone loss, particularly in cortical bone regions. These risks must be weighed against the benefits of LT4 therapy in individual patients.

Two cases of therapeutic failure associated with levothyroxine brand interchange.

OBJECTIVE: To report the loss of therapeutic control in 2 hypothyroid patients and remind clinical pharmacists and other healthcare professionals to remain cognizant of possible product quality differences within or bioequivalency differences between levothyroxine products. CASE SUMMARIES: Two patients with stable hypothyroidism experienced symptoms of hypothyroidism with increased serum thyroid-stimulating hormone (TSH) concentrations after switching from 1 levothyroxine product to another. One tablet from 1 of the patient's levothyroxine prescriptions was assayed, and its levothyroxine content was 74.5% of the label claim, a value outside of the United States Pharmacopeia requirements of 90-110%. DISCUSSION: Two patients with hypothyroidism had remained euthyroid and stable while receiving 1 levothyroxine product, but became symptomatic with dramatically increased serum TSH concentrations while receiving what were thought to be comparable dosages of another levothyroxine product. Therapeutic control was reestablished in both patients after therapy with the original levothyroxine product was reinstated. CONCLUSIONS: Clinical pharmacists and other healthcare professionals should remain cognizant of possible product quality differences within or bioequivalency differences between levothyroxine products. These differences necessitate close monitoring of hypothyroid patients, counseling these patients about the clinical signs of sub- and supratherapeutic levothyroxine dosages, and prudence when switching patients with stable hypothyroidism to alternative levothyroxine products. If there are inconsistencies between levothyroxine products, resultant deleterious effects on the therapeutic stability of patients with hypothyroidism may undermine cost savings that might be incurred by such a change. If these patients are switched to alternative levothyroxine products, it is recommended that thyroid function tests be repeated after equilibration to the new product.