Assessing the effects of thyroid suppression on benign solitary thyroid nodules. A model for using quantitative research synthesis

Role of cytological characteristics of benign thyroid nodules on effectiveness of their treatment with levothyroxine

INTRODUCTION

Levothyroxine (LT4) therapy has been used for the treatment of euthyroid nodular goiter, but there are controversial results about its usefulness. We aimed to evaluate the possible role of benign nodules' cytological characteristics in response to LT4 therapy.

MATERIAL AND METHODS

In total, 93 patients with 128 nodules were included in the study; 74 of the nodules were treated with LT4 (group 1), and 54 of them had no medication (group 2). The subgroups consisted of adenomatous nodules, colloid nodules and cystic nodules.

RESULTS

In group 1, mean thyroid volume and mean nodule volume were reduced significantly (p = 0.002 and p = 0.022, respectively) with low-normal level thyrotropin (TSH) suppression (between 0.3 mIU/ml and 1.0 mIU/ml), while there were no significant changes in group 2. When we evaluated changes of the initial and last nodule volumes in cytological subgroups, only colloid nodules in group 1 had significant reduction (p = 0.040) and the others had no significant changes. By omitting the colloid nodules, when the other nodules were revaluated, there were no significant changes in either group.

CONCLUSIONS

On the basis of these results, obtained from a large sample of Anatolian patients, it is possible that LT4 therapy leads to significant reductions of both thyroid volume and nodule size in colloid nodules, but not in other kinds of benign nodules.

Thyroxine suppression therapy for benign, non-functioning solitary thyroid nodules: a quality-effects meta-analysis

Levothyroxine (LT4) suppressive therapy for solitary thyroid nodules is not popularly advocated presently because its clinical efficacy and safety are currently considered controversial. This meta-analysis aims to address efficacy issues by using rigorous methods to arrive at a pooled estimate. On the basis of the analysis, it is estimated that LT4 therapy is clearly associated with up to a two-fold increase in the chance of nodule reduction. This translates to a number needed to treat (NNT) of 6 or a 50% decrease in the risk of cancer given nodule reduction. Keeping this definition of efficacy in mind and a low incidence of adverse events with low level LT4 suppression, such an intervention might be appropriate in patients selected on the basis of a low risk for adverse effects.

American Association of Clinical Endocrinologists and Associazione Medici Endocrinologi medical guidelines for clinical practice for the diagnosis and management of thyroid nodules

Thyroid nodules are common and are frequently benign. Current data suggest that the prevalence of palpable thyroid nodules is 3% to 7% in North America; the prevalence is as high as 50% based on ultrasonography (US) or autopsy data. The introduction of sensitive thyrotropin (thyroid-stimulating hormone or TSH) assays, the widespread application of fine-needle aspiration (FNA) biopsy, and the availability of high-resolution US have substantially improved the management of thyroid nodules. This document was prepared as a collaborative effort between the American Association of Clinical Endocrinologists (AACE) and the Associazione Medici Endocrinologi (AME). Most Task Force members are members of AACE. We have used the AACE protocol for clinical practice guidelines, with rating of available evidence, linking the guidelines to the strength of recommendations. Key observations include the following. Although most patients with thyroid nodules are asymptomatic, occasionally patients complain of dysphagia, dysphonia, pressure, pain, or symptoms of hyperthyroidism or hypothyroidism. Absence of symptoms does not rule out a malignant lesion; thus, it is important to review risk factors for malignant disease. Thyroid US should not be performed as a screening test. All patients with a palpable thyroid nodule, however, should undergo US examination. US-guided FNA (US-FNA) is recommended for nodules > or = 10 mm; US-FNA is suggested for nodules < 10 mm only if clinical information or US features are suspicious. Thyroid FNA is reliable and safe, and smears should be interpreted by an experienced pathologist. Patients with benign thyroid nodules should undergo follow-up, and malignant or suspicious nodules should be treated surgically. A radioisotope scan of the thyroid is useful if the TSH level is low or suppressed. Measurement of serum TSH is the best initial laboratory test of thyroid function and should be followed by measurement of free thyroxine if the TSH value is low and of thyroid peroxidase antibody if the TSH value is high. Percutaneous ethanol injection is useful in the treatment of cystic thyroid lesions; large,symptomatic goiters may be treated surgically or with radioiodine. Routine measurement of serum calcitonin is not recommended. Suggestions for thyroid nodule management during pregnancy are presented. We believe that these guidelines will be useful to clinical endocrinologists, endocrine surgeons, pediatricians, and internists whose practices include management of patients with thyroid disorders. These guidelines are thorough and practical, and they offer reasoned and balanced recommendations based on the best available evidence.

Changing Trends in Thyroid Practice: Understanding Nodular Thyroid Disease

OBJECTIVE

To describe changes that have occurred between 1952 and 2002 in the evaluation and management of nodular thyroid disease.

METHODS

A 30-year personal experience, institutional contributions, and the related published literature on evaluation of thyroid function and evolving strategies for management of thyroid nodules are reviewed.

RESULTS

Triiodothyronine (T(3)) was discovered in 1952, and measurement of plasma thyroxine by a competitive protein-binding technique became available in the 1960s. Late during that decade, the first radioimmunoassay for thyroid-stimulating hormone (TSH) was described, modified, and then used in clinical practice until the mid-1980s, when the more sensitive TSH assays became widely available. T(3) determination by radioimmunoassay was introduced early in the 1970s. Currently, sensitive thyroid function tests can detect early disease. In the general population, thyroid nodules have a prevalence higher than 50% after age 65 years, affecting more than 100 million people in the United States. Two important developments influenced thyroid nodule evaluation and management-- fine-needle aspiration (FNA) biopsy and ultrasonography. Because FNA biopsy has emerged as the most accurate test for nodule diagnosis, it has decreased the need for scanning and for thyroidectomy and thereby is likely to reduce health-care costs by more than $500 million annually in the United States. Thyroid ultrasonography is the imaging method of choice for evaluation of thyroid gland structure. Management of cytologically benign thyroid nodules remains controversial.

CONCLUSION

TSH seems to be only one of many factors in pathologic thyroid growth. FNA, because of its diagnostic accuracy, should be the initial procedure used in nodule evaluation.

Ultrasound thyroid nodule measurements: the "gold standard" and its limitations in clinical decision making

OBJECTIVE

To highlight the limitations associated with use of ultrasonography for the evaluation of thyroid nodule or gland volume for clinical decision making.

METHODS

We review the equipment (scanners and probes) used for ultrasonography and the appropriate measurements for assessment of thyroid nodules. The limitations of ultrasound thyroid measurements are summarized, particularly in reference to repeated measurements over time.

RESULTS

Thyroid ultrasonography is the recognized "gold standard" for an accurate and reliable assessment of gland volume and thyroid nodules. Many endocrinologists refer patients for surgical treatment because of detection of growth of thyroid nodules. In daily practice, they often make this decision by comparing ultrasound thyroid measurements determined over time. Although reliable, evaluation of thyroid nodule volume by ultrasonography has technologic, biologic, and examination technique limitations. These are particularly important in routine clinical practice, where ultrasound measurements are performed in less standardized settings than in experimental trials.

CONCLUSION

In daily medical office applications, ultrasound measurements of thyroid nodules should be used with caution in decision making.

Thyroid fine-needle aspiration biopsy: progress, practice, and pitfalls

OBJECTIVE

To provide an updated review of the current progress in, and the practice and pitfalls of, thyroid fine-needle aspiration (FNA) biopsy.

METHODS

The medical literature on the topic was reviewed, and the current methods, advantages, and controversies concerning FNA biopsy of thyroid nodules are summarized.

RESULTS

Thyroid nodules are a common clinical problem, with an estimated prevalence ranging from 19 to 35%. Most thyroid cancers manifest as thyroid nodules; however, only a small fraction of all thyroid nodules harbor malignant disease. Certain clinical features increase the likelihood of malignant involvement, but the absence of such features does not exclude the possibility of cancer. Of all currently available methods of evaluating nodular thyroid disease, FNA biopsy has been found to have the greatest diagnostic accuracy, approaching 95%, and its widespread use has resulted in substantial cost savings and has allowed a much better selection of patients in need of surgical treatment. The procedure, however, has two major limitations: nondiagnostic yield and indeterminate results. The approach to the management of patients with thyroid nodules is summarized.

CONCLUSION

FNA is the most reliable and cost-effective method of distinguishing benign from suspicious or malignant thyroid nodules.

Management of simple nodular goiter: current status and future perspectives

The simple nodular goiter, the etiology of which is multifactorial, encompasses the spectrum from the incidental asymptomatic small solitary nodule to the large intrathoracic goiter, causing pressure symptoms as well as cosmetic complaints. Its management is still the cause of considerable controversy. The mainstay in the diagnostic evaluation is related to functional and morphological characterization with serum TSH and (some kind of) imaging. Because malignancy is just as common in patients with a multinodular goiter as patients with a solitary nodule, we support the increasing use of fine-needle aspiration biopsy (cytology). Most patients need no treatment after malignancy is ruled out. In case of cosmetic or pressure symptoms, the choice in multinodular goiter stands between surgery, which is still the first choice, and radioiodine if uptake is adequate. In addition to surgery, the solitary nodule, whether hot or cold, can be treated with percutaneous ethanol injection therapy. If hot, radioiodine is the therapy of choice. Randomized studies are scarce, and the side effects of nonsurgical therapy are coming into focus. Therefore, the use of the optimum option in the individual patient cannot at present be based on evidence. However, we are of the view that levothyroxine, although widely used, should no longer be recommended routinely for this condition. Within a few years, the introduction of recombinant human TSH and laser therapy may profoundly alter the nonsurgical treatment of simple nodular goiter.

Effect of low- and high-dose levothyroxine on thyroid nodule volume: a crossover placebo-controlled trial

OBJECTIVE

The efficacy and the effective dose of levothyroxine suppressive therapy in the treatment of benign thyroid nodules are controversial. In this study, we aimed to determine the response of solitary thyroid nodules to low- or high-level TSH suppression in a placebo-controlled, randomized crossover trial.

DESIGN

Forty-nine patients with solitary thyroid nodules on palpation were randomized to high-level and low-level TSH suppression groups. In each group, patients were further randomized to placebo and active levothyroxine subgroups. Patients in each subgroup were crossed over to placebo or active levothyroxine at the end of the first year and were then followed up for an additional year.

METHODS

TSH levels were suppressed to 0.4-0.6 mIU/ml and < or = 0.01 mIU/ml in the low-level and high-level TSH suppression groups, respectively. Nodule volumes were measured at baseline and every 6 months after the desired level of TSH was reached if the patients were in the active levothyroxine treatment group or every 6 months if they were in the placebo group.

RESULTS

In high-level TSH suppression groups, nodule volume decreased significantly at the end of the active treatment periods (4.99 +/- 2.02 ml vs. 3.20 +/- 1.50 ml, P < 0.01, in Group 1; and 3.72 +/- 1.79 ml to 2.05 +/- 0.64 ml, P < 0.001, in Group 2). In the low-level TSH suppression groups, nodule volume also decreased significantly at the end of the active treatment periods (4.43 +/- 1.76 ml vs. 3.04 +/- 1.32, P < 0.05, in Group 3; and 3.59 +/- 0.89 ml to 2.22 +/- 0.59 ml, P < 0.01, in Group 4). Nodule volumes regained their original volumes during the placebo treatment periods. The percentage decline in clinically relevant nodule volume reduction (> or = 50%) was similar in the low-level and high-level TSH suppression groups.

CONCLUSION

Low- and high-level TSH suppression were equally effective in reducing nodule volume and thus, considering the complications of high-level TSH suppression, low-level TSH suppression should be used if one considers levothyroxine suppressive therapy to reduce thyroid nodule size.

Pharmacotherapy for thyroid nodules. A systematic review and meta-analysis

The review highlights the uncertainty in the management of nodular thyroid disease. Thyroxine suppressive treatment is given in the hope that nodules might decrease in size, sometimes assuming that dependency on TSH is different in benign and malignant nodular disease. Follow-up of benign nodules over 10 years suggested that most remain the same, shrink, or disappear [14]. TSH suppression may lead to hyperthyroidism, reduced bone density [37.39], and atrial fibrilation; however, apart from reduction of nodule size or arrest in nodule growth, thyroxine therapy may benefit patients by reducing perinodular volume. Consequently, both pressure symptoms and cosmetic complaints could improve. Unfortunately, no information concerning symptoms or well-being is available from published randomized trials. In conclusion, more high quality studies of sufficient duration with adequate power estimation are needed. Uncertainty about predictors of response or the impact on outcomes that are important to patients leaves considerable doubt about the wisdom of applying suppressive therapy. Future studies shoudl include patient-important outcomes including thyroid cancer incidence, health-related quality of life and costs.

Effects of thyroid hormone suppression therapy on adverse clinical outcomes in thyroid cancer

BACKGROUND

Long-term thyroid hormone (TH) therapy aiming at the suppression of serum thyrotropin (TSH) has been traditionally used in the management of well differentiated thyroid cancer (ThyrCa). However, formal validation of the effects of thyroid hormone suppression therapy (THST) through randomized controlled trials is lacking. Additionally, the role - if any - of TSH effect at low ambient concentrations upon human thyroid tumorigenesis remains unclear.

AIM

Evaluation of the effect of THST on the clinical outcomes of papillary and/or follicular ThyrCa.

METHODS

By using a quantitative research synthesis approach in a cumulative ThyrCa cohort, we evaluated the effect of THST on the likelihood of major adverse clinical events (disease progression/recurrence and death). A total of 28 clinical trials published during the period 1934-2001 were identified; only 10 were amenable to meta-analysis. Causality was assessed by Hill criteria.

RESULTS

Out of 4, 174 patients with ThyrCa, 2, 880 (69%) were reported as being on THST. Meta-analysis showed that the group of patients who received THST had a decreased risk of major adverse clinical events (RR = 0.73; Cl = 0.60-0.88; P < 0.05). Further, by applying a Likert scale, 15/17 interpretable studies showed either a 'likely' or 'questionable' beneficial effect of THST. Assessment of causality between TSHT and reduction of major adverse clinical events suggested a probable association.

CONCLUSIONS

THST appears justified in ThyrCa patients following initial therapy. As most primary studies were imperfect, future research will better define the effect of THST upon ThyrCa clinical outcomes.

Exaggerated levothyroxine malabsorption due to calcium carbonate supplementation in gastrointestinal disorders

OBJECTIVE

To describe a patient with primary hypothyroidism in whom ingestion of levothyroxine with calcium carbonate led to markedly elevated serum thyrotropin concentrations.

CASE SUMMARY

A 61-year-old white woman with primary hypothyroidism, systemic lupus erythematosus, celiac disease, and history of Whipple resection for pancreatic cancer was euthyroid with levothyroxine 175-188 micrograms/d. After taking a high dose of calcium carbonate (1250 mg three times daily) with levothyroxine, she developed biochemical evidence of hypothyroidism (thyrotropin up to 41.4 mU/L) while remaining clinically euthyroid. Delaying calcium carbonate administration by four hours returned her serum thyrotropin to a borderline high concentration (5.7 mU/L) within a month. Serum concentrations of unbound and total thyroxine and triiodothyronine tended to decrease, but remained borderline low to normal while the patient concomitantly received levothyroxine and calcium carbonate.

DISCUSSION

Concomitant administration of levothyroxine and calcium carbonate often results in levothyroxine malabsorption. While in most patients the clinical consequences of this interaction, even with prolonged exposure, are relatively small, overt hypothyrodism may develop in patients with preexisting malabsorption disorders. However, as the current case illustrates, the clinical manifestations of the initial levothyroxine deficit may not always be apparent and, of all usual laboratory thyroid function tests, only thyrotropin measurement will reliably uncover the exaggerated levothyroxine malabsorption.

CONCLUSIONS

Decreased absorption of levothyroxine when given with calcium carbonate may be particularly pronounced in patients with preexisting malabsorption disorders. Once recognized, a change in drug administration schedule usually minimizes or eliminates this interaction.