Low serum thyroglobulin as a clue to the diagnosis of thyrotoxicosis factitia

Clinical use of thyroglobulin: not only thyroid cancer

Thyroglobulin (TG) is a dimeric glycoprotein produced exclusively by mature thyroid tissue and stored within the follicular lumen. It is essential for the organification of iodine and the production of thyroid hormones. The concentration of TG in the bloodstream varies between individuals and depends on factors such as thyroid mass, stimulation of the gland by thyrotropin or autoantibodies, and tissue destruction. TG is essential to monitor patients with differentiated thyroid cancer; however, its use is not limited only to this clinical entity. Measurement of circulating TG can provide better insight into numerous clinical scenarios, such as destructive thyroiditis, presence of ectopic thyroid tissue, thyroid trauma, factitious thyrotoxicosis, or iodine nutrition. Lately, TG has found its new clinical use in immune checkpoint-related thyroid dysfunction. TG measurement should be performed carefully in patients with antithyroglobulin antibodies due to possible laboratory interferences. In this review, we offer a summary of current knowledge about the clinical use of TG and the implications it brings to daily practice.

Toxicity from illegitimate slimming agents - a 10-year case series at a tertiary toxicology laboratory in Hong Kong

CONTEXT

This retrospective case-series study aims to provide an overview of the clinical, biochemical and analytical findings in patients who presented with toxicity related to the use of illegitimate slimming agents in Hong Kong from the perspective of a tertiary referral toxicology laboratory.

METHODS

All clinical cases referred to the Hospital Authority Toxicology Reference Laboratory, Hong Kong with clinical suspicion of illegitimate slimming agent-related toxicity between January 2008 and December 2017 were reviewed retrospectively. The use of illegitimate slimming agents included the use of (1) deregistered slimming agents, (2) drug analogues that were not registered drugs, (3) registered drugs not approved for the indication of weight reduction (whether prescribed by a doctor or not), and (4) prescription-only slimming agents without a doctor's prescription. Patients taking registered weight-reducing drugs prescribed by a doctor were excluded. Patient demographics, clinical features, relevant laboratory investigations, and toxicological findings were analyzed.

RESULTS

From 2008 to 2017, a total of 346 patients were analytically confirmed by our laboratory to have clinical toxicity related to the use of illegitimate slimming agents. The median age of the patients was 27 years and 92.5% of the patients were female. The most common clinical presentations included psychiatric features, sympathomimetic toxicity, hypokalemia, and abnormal thyroid function tests. Fatal or severe clinical toxicity was observed in 10% of the cases. The major classes of drugs detected on our analytical platforms were stimulants (e.g., sibutramine), laxatives (e.g., anthraquinones), diuretics (e.g., hydrochlorothiazide), and thyroid hormones (e.g., animal thyroid tissue). These illegitimate slimming agents were obtained from various sources including the Internet, over-the-counter in community pharmacy, or unspecified local sources.

DISCUSSION AND CONCLUSIONS

The use of slimming agents is common worldwide; apart from taking registered slimming agents prescribed by registered practitioners, many users obtain slimming agents from various illegitimate sources. The unregulated use of these drugs can be associated with significant clinical toxicity. This study provides a current landscape of illegitimate slimming agent toxicity in Hong Kong to frontline clinicians and other toxicology professionals. Collaboration between clinicians, laboratories, and government authorities would be imperative to prevent further health adversities related to the misuse of these agents.

Factitious thyrotoxicosis: how to find it

Background

Although the most common cause of thyrotoxicosis is Graves’ disease, the determination of the cause of thyrotoxicosis is important for establishing appropriate management. Diagnosis of surreptitious ingestion of thyroid hormones or factitious thyrotoxicosis often presents a difficult challenge especially in a patient with previously diagnosed Graves’ disease. The objective of this report was to demonstrate various approaches to support the diagnosis of factitious thyrotoxicosis.

Case presentation

We describe a patient with underlying Graves’ disease who underwent definitive therapy and needed long-term levothyroxine (LT4) replacement therapy. Later she developed thyrotoxicosis. Although factitious thyrotoxicosis was suspected because of very low thyroid uptake and low thyroglobulin (Tg) levels with the absence of thyroglobulin antibodies (TgAbs), she still refused any medication or substance use. After the administration of bile acid sequestrant, the thyroid hormone levels rapidly returned to normal within 1 month.

Conclusions

The diagnosis of factitious thyrotoxicosis is based upon the absence of goiter, suppressed serum Tg level, decreased radioactive iodine (RAI) uptake, and excellent response after cholestyramine treatment.

Thyroid detectives: on the trail of Munchausen's syndrome

Thyrotoxicosis factitia, a disorder frequently seen in young or middle-aged women with psychological disorders, most commonly results from surreptitious ingestion of excess thyroid hormones. In most patients, diagnosis is relatively straightforward and depends on the demonstration of biochemical thyrotoxicosis, suppressed endogenous thyroid function and absence of clinical features of underlying thyroid disease. However, at times, confounding factors can make the diagnosis particularly challenging and necessitate the investigating physician to don the detective's cap to get to the root of the problem. We discuss a patient whose diagnosis was reached with ingenuity after considerable effort from four endocrinologists having a total experience of 37 years in their field.

Factors associated with serum thyroglobulin in a Ukrainian cohort exposed to iodine-131 from the accident at the Chernobyl Nuclear Plant

BACKGROUND

Serum thyroglobulin (Tg) is associated with the presence of thyroid disease and has been proposed as a biomarker of iodine status. Few studies have examined factors related to serum Tg in populations environmentally exposed to ionizing radiation and living in regions with endemic mild-to-moderate iodine deficiency.

METHODS

We screened 10,430 individuals who were living in Ukraine and under 18 years of age at the time of the 1986 Chernobyl Nuclear Power Plant accident for thyroid disease from 2001 to 2003. We estimated the percent change (PC) in serum Tg associated with demographic factors, iodine-131 thyroid dose, and indicators of thyroid structure and function using linear regression. We also examined these relationships for individuals with and without indications of thyroid abnormality.

RESULTS

Mean and median serum Tg levels were higher among participants with abnormal thyroid structure/function. Percent change in serum Tg increased among females, smokers and with older age (p-values<0.001), and Tg increased with increasing thyroid volume, and serum thyrotropin (p-values for trend<0.001). We found no evidence of significant associations between iodine-131 thyroid dose and Tg. Serum Tg levels were inversely associated with iodized salt intake (PC=-7.90, 95% confidence interval: -12.08, -3.52), and over the range of urinary iodine concentration, the odds of having elevated serum Tg showed a U-shaped curve with elevated Tg at low and high urinary iodine concentrations.

CONCLUSION

Serum Tg may be a useful indicator of population iodine status and a non-specific biomarker of structural and functional thyroid abnormalities in epidemiological studies.

2016 American Thyroid Association Guidelines for Diagnosis and Management of Hyperthyroidism and Other Causes of Thyrotoxicosis

BACKGROUND

Thyrotoxicosis has multiple etiologies, manifestations, and potential therapies. Appropriate treatment requires an accurate diagnosis and is influenced by coexisting medical conditions and patient preference. This document describes evidence-based clinical guidelines for the management of thyrotoxicosis that would be useful to generalist and subspecialty physicians and others providing care for patients with this condition.

METHODS

The American Thyroid Association (ATA) previously cosponsored guidelines for the management of thyrotoxicosis that were published in 2011. Considerable new literature has been published since then, and the ATA felt updated evidence-based guidelines were needed. The association assembled a task force of expert clinicians who authored this report. They examined relevant literature using a systematic PubMed search supplemented with additional published materials. An evidence-based medicine approach that incorporated the knowledge and experience of the panel was used to update the 2011 text and recommendations. The strength of the recommendations and the quality of evidence supporting them were rated according to the approach recommended by the Grading of Recommendations, Assessment, Development, and Evaluation Group.

RESULTS

Clinical topics addressed include the initial evaluation and management of thyrotoxicosis; management of Graves' hyperthyroidism using radioactive iodine, antithyroid drugs, or surgery; management of toxic multinodular goiter or toxic adenoma using radioactive iodine or surgery; Graves' disease in children, adolescents, or pregnant patients; subclinical hyperthyroidism; hyperthyroidism in patients with Graves' orbitopathy; and management of other miscellaneous causes of thyrotoxicosis. New paradigms since publication of the 2011 guidelines are presented for the evaluation of the etiology of thyrotoxicosis, the management of Graves' hyperthyroidism with antithyroid drugs, the management of pregnant hyperthyroid patients, and the preparation of patients for thyroid surgery. The sections on less common causes of thyrotoxicosis have been expanded.

CONCLUSIONS

One hundred twenty-four evidence-based recommendations were developed to aid in the care of patients with thyrotoxicosis and to share what the task force believes is current, rational, and optimal medical practice.

Pseudohyperthyroxinemia in a hypothyroid patient secondary to chronic phlegmon

Background: Elevated free thyroxine could be primary or secondary, endogenous or exogenous and often presents with symptoms of hyperthyroidism. Thyroxine levels are low in hypothyroidism, where the individual requires exogenous supplementation to maintain a euthyroid state. However, thyroxine levels may be elevated in a hypothyroid patient because of over-supplementation/over-suppression with exogenous agent(s) or secondary to other pathologies and rarely, laboratory error or assay interference may cause alteration in the levels of the thyroid hormones.

Case report: A 44-year-old man with well controlled hypothyroidism was referred for assessment of markedly elevated TSH and free thyroxine levels with low free T3. Clinically the patient was hypothyroid with symptoms of fatigue and weight gain of 30 pounds over the past 3-months and the TSH levels were consistent with marked hypothyroidism. However, free thyrxoine was markedly elevated, opposite of what to be expected. A systematic evaluation, presented here, was helpful in the diagnosis of pseudohyperthyroxinemia secondary to assay interferences in a timely fashion, avoiding unnecessary further investigations.

Conclusions: Interference in immunoassays is an important clinical problem that is underestimated and can have important clinical consequences. It is important to recognize the possibility of such interferences early in the diagnostic process and to implement protocols to identify these whenever possible, in a timely fashion, to prevent untoward consequences. Vigilance by both the clinician and the laboratory staff is important.

The Brazilian consensus for the diagnosis and treatment of hyperthyroidism: recommendations by the Thyroid Department of the Brazilian Society of Endocrinology and Metabolism

INTRODUCTION

Hyperthyroidism is characterized by increased synthesis and release of thyroid hormones by the thyroid gland. Thyrotoxicosis refers to the clinical syndrome resulting from excessive circulating thyroid hormones, secondary to hyperthyroidism or due to other causes. This article describes evidence-based guidelines for the clinical management of thyrotoxicosis.

OBJECTIVE

This consensus, developed by Brazilian experts and sponsored by the Department of Thyroid Brazilian Society of Endocrinology and Metabolism, aims to address the management, diagnosis and treatment of patients with thyrotoxicosis, according to the most recent evidence from the literature and appropriate for the clinical reality of Brazil.

MATERIALS AND METHODS

After structuring clinical questions, search for evidence was made available in the literature, initially in the database MedLine, PubMed and Embase databases and subsequently in SciELO - Lilacs. The strength of evidence was evaluated by Oxford classification system was established from the study design used, considering the best available evidence for each question.

RESULTS

We have defined 13 questions about the initial clinical approach for the diagnosis and treatment that resulted in 53 recommendations, including the etiology, treatment with antithyroid drugs, radioactive iodine and surgery. We also addressed hyperthyroidism in children, teenagers or pregnant patients, and management of hyperthyroidism in patients with Graves' ophthalmopathy and various other causes of thyrotoxicosis.

CONCLUSIONS

The clinical diagnosis of hyperthyroidism usually offers no difficulty and should be made with measurements of serum TSH and thyroid hormones. The treatment can be performed with antithyroid drugs, surgery or administration of radioactive iodine according to the etiology of thyrotoxicosis, local availability of methods and preferences of the attending physician and patient.

Munchausen syndrome and factitious disorder: the role of the laboratory in its detection and diagnosis

The term Munchausen syndrome is used to describe the patient who chronically fabricates or induces illness with the sole intention of assuming the patient role. Such persons often have a close association with the medical profession and thus use their knowledge to falsify symptoms and laboratory specimens to mimic disease. Cases of factitious disease have appeared in the literature originating from all medical specialties, and include such rare disorders as phaeochromocytoma and Bartter's syndrome. The laboratory can play a key role in the detection and diagnosis of factitious disorders. Indeed discrepant biochemistry results may provide the first clue to the diagnosis. Laboratory staff should be particularly aware of highly variable test results and extreme abnormalities that are not consistent with the wider biochemical profile, suggesting sample tampering. Factitious disorder should also be included in the clinician's differential diagnosis when disease presentation is unusual or an underlying cause cannot be found. Investigation to exclude or confirm factitious disorder at an early stage can prevent unnecessary testing in the search for increasingly rare diseases. Appropriate analyses may include screening tests for the detection of surreptitious drug administration or replication of a fabricated sample to confirm the method used. In all cases close communication between the clinician and laboratory is essential. This will ensure that appropriate tests are conducted particularly with regard to time critical and repeat tests.

Factors associated with serum thyroglobulin levels in a population living in Belarus

OBJECTIVE

Serum thyroglobulin (Tg) has been associated with a number of thyroid disorders and has been proposed as an indicator of iodine deficiency in a population. However, few studies have addressed the epidemiology of Tg in a population-based setting or in the context of exposure to radioactive iodine-131 (I-131). Our objective was to evaluate baseline levels of Tg in relation to sociodemographic characteristics, iodine status and thyroid function for individuals exposed to I-131.

DESIGN

A population-based cohort assembled in Belarus following the Chornobyl accident provided demographic factors, clinical data and physiological measurements.

PARTICIPANTS

Our analytical sample included 10,344 subjects of whom 7890 had no thyroid disease and 2454 had evidence of structural or functional thyroid abnormality.

MEASUREMENTS

Standardized assays were used to measure serum Tg, urinary iodine, TSH and antibodies to Tg and thyroid peroxidase. Ultrasound was used to assess the presence of nodules and estimate thyroid volume.

RESULTS

In the fully adjusted model, percent change in Tg was significantly increased among females, smokers and subjects of older age and Tg increased with decreasing urinary iodine concentration, increasing serum TSH and increasing thyroid volume (P-values for trend <0·0001), and presence of thyroid nodules (P < 0·05). We found a complex interaction between region of residence, rural/urban living, presence/absence of thyroid abnormalities and serum Tg (P < 0·0001).

CONCLUSIONS

In residents of Belarus, serum Tg is significantly related to presence of thyroid abnormalities as well as indicators of thyroid function and iodine deficiency and, therefore, could be used to characterize the iodine status and thyroid function of individuals in the context of epidemiological study.

Can we interpret serum thyroglobulin results?

Thyroglobulin (Tg) is a tumour marker for differentiated thyroid cancer. Interpretation requires a knowledge of the current thyrotropin (TSH) concentration as secretion is TSH-dependent. While a raised serum Tg may be indicative of residual or recurrent thyroid cancer, trauma to the thyroid (e.g. surgical, biopsy or due to radioiodine treatment) also causes an increase. Tg may be measured when TSH is suppressed and also following recombinant TSH (rhTSH) stimulation. Interpretation of results in pregnancy and in children is discussed. Assay bias and interference by endogenous Tg antibodies (Abs) are the main confounders in the interpretation of results. Although there is an international standard for Tg, there are large differences in results and yet there are few assay-specific clinical decision limits. Patients should therefore be monitored with the same assay. Endogenous TgAbs may cause false-negative interference in immunometric assays and may cause false-positive results in radioimmunoassay. Although the measurement of TgAbs has been advocated for predicting interference, it is now clear that interference can still occur when TgAbs have not been detected, the effect being TgAb-assay-specific. Approaches to identifying those samples where there may be interference are discussed. The laboratory should have a protocol for the investigation of possible interferences and data on the bias of the Tg assay that they use. An appreciation of the clinical uses of the service is required as an understanding by endocrinologists, oncologists and endocrine surgeons of the analytical limitations of the service.

Thyrotoxicosis

Hyperthyroidism describes the sustained increase in thyroid hormone biosynthesis and secretion by a thyroid gland with increased metabolism. Although the use of radioiodine scanning serves as a useful surrogate that may help characterize the cause of thyrotoxicosis, it only indirectly addresses the underlying physiologic mechanism driving the increase in serum thyroid hormones. In this article, thyrotoxic states are divided into increased or decreased thyroid metabolic function. In addition to the diagnosis, clinical presentation, and treatment of the various causes of hyperthyroidism, a section on functional imaging and appropriate laboratory testing is included.

Hyperthyroidism and other causes of thyrotoxicosis: management guidelines of the American Thyroid Association and American Association of Clinical Endocrinologists

OBJECTIVE

Thyrotoxicosis has multiple etiologies, manifestations, and potential therapies. Appropriate treatment requires an accurate diagnosis and is influenced by coexisting medical conditions and patient preference. This article describes evidence-based clinical guidelines for the management of thyrotoxicosis that would be useful to generalist and subspeciality physicians and others providing care for patients with this condition.

METHODS

The development of these guidelines was commissioned by the American Thyroid Association in association with the American Association of Clinical Endocrinologists. The American Thyroid Association and American Association of Clinical Endocrinologists assembled a task force of expert clinicians who authored this report. The task force examined relevant literature using a systematic PubMed search supplemented with additional published materials. An evidence-based medicine approach that incorporated the knowledge and experience of the panel was used to develop the text and a series of specific recommendations. The strength of the recommendations and the quality of evidence supporting each was rated according to the approach recommended by the Grading of Recommendations, Assessment, Development, and Evaluation Group.

RESULTS

Clinical topics addressed include the initial evaluation and management of thyrotoxicosis; management of Graves' hyperthyroidism using radioactive iodine, antithyroid drugs, or surgery; management of toxic multinodular goiter or toxic adenoma using radioactive iodine or surgery; Graves' disease in children, adolescents, or pregnant patients; subclinical hyperthyroidism; hyperthyroidism in patients with Graves' ophthalmopathy; and management of other miscellaneous causes of thyrotoxicosis.

CONCLUSIONS

One hundred evidence-based recommendations were developed to aid in the care of patients with thyrotoxicosis and to share what the task force believes is current, rational, and optimal medical practice.

Thyrotoxicosis-induced acute myocardial infarction due to painless thyroiditis

BACKGROUND

Thyrotoxicosis influences cardiovascular hemodynamics and can induce coronary vasospasm. Patients with thyrotoxicosis-induced acute myocardial infarction (AMI) are unusual and almost all reported cases have been associated with Graves' disease. Patients with painless thyroiditis show a thyrotoxic phase during the early stages. Here we describe a very rare case of thyrotoxicosis with painless thyroiditis-induced AMI.

SUMMARY

A 35-year-old Korean man visited the emergency room for a 2-hour duration of typical AMI chest pain. The patient did not have any coronary artery disease (CAD) risk factors. The electrocardiogram showed 3 mm of ST-segment elevation in leads II, III, and aVF, which is consistent with inferior AMI. We immediately treated the patient with aspirin, clopidogrel, and nitroglycerine and performed emergent coronary angiography. Coronary angiography showed normal coronary arteries without any stenotic lesions. Consistent with AMI, cardiac enzyme levels of serum creatine kinase (CK), CK-MB, and troponin-I were also elevated. Laboratory findings showed thyrotoxicosis without any thyroid autoantibodies. A 99m-technetium scintigraphy showed markedly decreased thyroid uptake compatible with thyroiditis. We treated the patient with calcium channel blockers and nitrates. The patient spontaneously recovered normal thyroid function after 6 weeks of observation and did not complain of chest pain.

CONCLUSION

Thyrotoxicosis due to painless thyroiditis provoked AMI in a young man who had no atherosclerotic coronary lesions and no CAD risk factors.

Hyperthyroidism from autoimmune thyroiditis in a man with type 1 diabetes mellitus: a case report

Introduction

The presentation, diagnosis, clinical course and treatment of a man with hyperthyroidism secondary to autoimmune thyroiditis in the setting of type 1 diabetes mellitus has not previously been described.

Case presentation

A 32-year-old European-American man with an eight-year history of type 1 diabetes mellitus presented with an unintentional 22-pound weight loss but an otherwise normal physical examination. Laboratory studies revealed a suppressed thyroid-stimulating hormone concentration and an elevated thyroxine level, which are consistent with hyperthyroidism. His anti-thyroid peroxidase antibodies were positive, and his thyroid-stimulating immunoglobulin test was negative. Uptake of radioactive iodine by scanning was 0.5% at 24 hours. The patient was diagnosed with autoimmune thyroiditis. Six weeks following his initial presentation he became clinically and biochemically hypothyroid and was treated with thyroxine.

Conclusion

This report demonstrates that autoimmune thyroiditis presenting as hyperthyroidism can occur in a man with type 1 diabetes mellitus. Autoimmune thyroiditis may be an isolated manifestation of autoimmunity or may be part of an autoimmune polyglandular syndrome. Among patients with type 1 diabetes mellitus who present with hyperthyroidism, Graves' disease and other forms of hyperthyroidism need to be excluded as autoimmune thyroiditis can progress quickly to hypothyroidism, requiring thyroid hormone replacement therapy.

Hyperthyroidism and other causes of thyrotoxicosis: management guidelines of the American Thyroid Association and American Association of Clinical Endocrinologists

BACKGROUND

Thyrotoxicosis has multiple etiologies, manifestations, and potential therapies. Appropriate treatment requires an accurate diagnosis and is influenced by coexisting medical conditions and patient preference. This article describes evidence-based clinical guidelines for the management of thyrotoxicosis that would be useful to generalist and subspeciality physicians and others providing care for patients with this condition.

METHODS

The development of these guidelines was commissioned by the American Thyroid Association in association with the American Association of Clinical Endocrinologists. The American Thyroid Association and American Association of Clinical Endocrinologists assembled a task force of expert clinicians who authored this report. The task force examined relevant literature using a systematic PubMed search supplemented with additional published materials. An evidence-based medicine approach that incorporated the knowledge and experience of the panel was used to develop the text and a series of specific recommendations. The strength of the recommendations and the quality of evidence supporting each was rated according to the approach recommended by the Grading of Recommendations, Assessment, Development, and Evaluation Group.

RESULTS

Clinical topics addressed include the initial evaluation and management of thyrotoxicosis; management of Graves' hyperthyroidism using radioactive iodine, antithyroid drugs, or surgery; management of toxic multinodular goiter or toxic adenoma using radioactive iodine or surgery; Graves' disease in children, adolescents, or pregnant patients; subclinical hyperthyroidism; hyperthyroidism in patients with Graves' ophthalmopathy; and management of other miscellaneous causes of thyrotoxicosis.

CONCLUSIONS

One hundred evidence-based recommendations were developed to aid in the care of patients with thyrotoxicosis and to share what the task force believes is current, rational, and optimal medical practice.

Toxic multinodular goiter with low radioactive iodine uptake

A 74-year-old woman was referred to our hospital for goiter and persistent thyrotoxicosis. She had no signs of ophthalmopathy. She was not taking thyroid hormone. Thyroid CT revealed multiple nodules. The thyroid gland was not detected on (99m)Tc scintigraphy, (123)I uptake rate was 4.5% at 24 hours without hot nodules, and aberrant goiter was negative. After partial thyroidectomy, she was treated with levothyroxine. TRAb was undetectable during the disease course, and focal destructive change or chronic lymphocytic thyroiditis on the pathological specimens was not evident. We report a rare case of toxic multinodular goiter with low radioactive iodine uptake.

Outbreak of exogenous Cushing's syndrome due to unlicensed medications

OBJECTIVE

Despite the widespread medical use of glucocorticoids, reports of factitious administration of these hormones have been uncommon. We herein report an outbreak of Cushing's syndrome in Tehran among the addicts using Tamgesic (a brand of Buprenorphine) to help them through the narcotic withdrawal stage, without knowledge of the glucocorticoid content of the black-market drug.

DESIGN AND MEASUREMENTS

Case histories of 19 patients with a final diagnosis of iatrogenic Cushing's syndrome were reviewed. Liquid chromatography/mass spectrometry (LC-Mass) method was used to evaluate glucocorticoid existence in the brand. High performance liquid chromatography was used to determine plasma dexamethasone level.

RESULTS

No buprenorphine was present in the vials. Each Tamgesic vial contained 0.4 mg of Dexamethasone disodium phosphate; Heroin was also found in them. The duration of injection abuse and the total dexamethasone intake was 4.5 (1-18) months and 2.6 (0.8-8) mg/day, respectively. Median plasma dexamethasone concentration was 5.8 nmol/l, with a range of 5-8.7. Physical findings of the cases were not different from those of the classic endogenous Cushing's syndrome but their serum cortisol and urinary free cortisol were suppressed. Severe life-threatening complications were demonstrated in five cases.

CONCLUSION

Surreptitious use of steroids resulting in Cushing's syndrome may be more common in opium addicts; a high degree of suspicion is needed to uncover this disorder. Whenever facing a cushingoid appearance in addicts, the possibility of using black market drugs with corticosteroid contents should be kept in mind.

Thyrotoxicosis factitia masquerading as recurrent Graves' disease: endogenous antibody immunoassay interference, a pitfall for the unwary

Antibody interference in immunoassays is an underestimated problem, which has the potential to cause patient harm and waste health-care resources. We report a case where thyroglobulin antibodies generated a false-positive thyroglobulin result delaying the diagnosis of thyrotoxicosis factitia masquerading as recurrent Graves' disease. A high index of clinical suspicion and good laboratory-clinician communication underpins effective clinical and laboratory strategies to detect potentially erroneous laboratory results due to endogenous antibody interference in immunoassays.

Serum thyroglobulin levels after fine-needle aspiration of thyroid nodules

OBJECTIVE

To investigate whether a minor insult to the thyroid gland attributable to fine-needle aspiration (FNA) or external thyroid palpation can cause a release of serum thyroglobulin (Tg) into the circulation.

METHODS

We determined serum Tg levels before and at 60 minutes and 15 days after FNA in 25 patients with thyroid nodules. Results were compared with those obtained in 25 patients with thyroid nodules, in whom serum Tg concentrations were determined before and 60 minutes after palpation of the thyroid, and in 15 healthy subjects without thyroid disease, who had no thyroid palpation and no FNA, from whom 2 blood specimens were obtained 60 minutes apart. All participants had normal results of thyroid function tests and no detectable antithyroglobulin or thyroid peroxidase antibodies.

RESULTS

After FNA, 22 of 25 patients had significant elevation of serum Tg concentrations. The Tg levels returned to baseline values 15 days after FNA. In 4 of the 25 patients with thyroid nodules who had palpation of the thyroid, a significant increase in serum Tg levels was elicited. None of the 15 healthy subjects with normal thyroid glands (and with no FNA or thyroid palpation) had significant Tg elevations.

CONCLUSION

FNA causes a significant increase in serum Tg concentrations, which may persist for 15 days. Therefore, Tg assay should not be scheduled prematurely after FNA.

Thyroglobulin autoantibody levels below the cut-off for positivity can interfere with thyroglobulin measurement

Antithyroglobulin antibodies can interfere with the measurement of thyroglobulin yielding spuriously high or low levels depending on the method used. Interference is unrelated to the antibody concentration and can occur at very low concentrations. We report a patient in whom antithyroglobulin antibodies below the cut-off for positivity nearly led to an incorrect diagnosis of thyrotoxicosis factitia.

Importance of the Detection Method for Thyroglobulin Antibodies for the Validity of Thyroglobulin Measurements in Sera from Patients with Graves Disease

Background: The use of recovery tests has been proposed to disclose interferences from anti-thyroglobulin antibodies (TgAbs) in thyroglobulin (Tg) assays. We studied the value of a recovery test in Tg measurement by a new commercial IRMA.

Methods: Blood samples were collected from 153 patients with untreated Graves disease. Tg and TgAbs were measured by IRMA and RIA, respectively (Dynotest Tg-plus and Dynotest anti-Tgn; Brahms Diagnostica). The recoveries of added amounts of Tg were calculated for each serum.

Results: TgAbs were detected in 72 of the 153 patients (47%). The recovery test results for the 81 TgAb-negative sera (median, 101%; range, 80–115%) were identical to the results for the 91 controls (median, 102%; range, 80–124%). By contrast, significantly lower recovery test results were observed for the 72 TgAb-positive sera (median, 79%; range, 60–103%; Z = −8.363; P &lt;0.0001). In the 34 of the 72 TgAb-positive sera with a normal recovery test, Tg concentrations were significantly lower (median Tg, 13.6 μg/L; range, 1.1–360 μg/L) than those measured in the TgAb-negative sera (median, 107 μg/L; range, 1.2–700 μg/L; Z = −3.797; P &lt;0.0001).

Conclusions: Tg values were decreased in TgAb-positive sera even when the results of the recovery tests were normal. This test should not be used alone to determine the validity of a serum Tg measurement in Graves disease.

Serum thyroglobulin measurement. Utility in clinical practice

Serum thyroglobulin measurement has greatly facilitated the clinical management of patients with differentiated thyroid cancer and a variety of other thyroid disorders. Thyroglobulin autoantibodies remain a significant obstacle to the clinical use of thyroglobulin measurement. The interpretation of any given thyroglobulin value requires the careful synthesis of all pertinent clinical and laboratory data available to the clinician. The diagnostic use of rhTSH-stimulated thyroglobulin levels has greatly facilitated the follow-up of low-risk patients with thyroid cancer. Although the measurement of thyroglobulin mRNA from peripheral blood is likely to affect the future management of these patients, it is expected that serum thyroglobulin measurement will continue to have a principal role in the care of patients with differentiated thyroid cancer.

Serum and tissue thyroglobulin measurement: clinical applications in thyroid disease

Since the first demonstration by Van Herle et al. that thyroglobuling (Tg), the main iodo-protein of the thyroid gland, was detectable in the circulation of normal subjects by using specific radioimmunoassay, an impressive amount of papers has been produced, describing several clinical applications of Tg measurements. Now, measurement of Tg is the mainstay in the post-surgical follow-up of differentiated thyroid cancer and an integral part in the diagnostic evaluation of patients with benign thyroid diseases. In this article we will review the most relevant clinical application of Tg measurements in the blood and in other biological material, including: a) serum Tg in perinatal age and congenital hypothyroidism; b) serum Tg measurements in thyrotoxicosis factitia and in other thyrotoxic conditions associated with low iodine uptake; c) differential diagnosis of thyroid and parathyroid cysts; and d) clinical relevance of Tg measurement in thyroid cancer.

The age of patients with thyrotoxicosis factitia in Italy from 1973 to 1996

Thyrotoxicosis factitia, a syndrome due to the surreptitious ingestion of excess thyroid hormones, has generally been diagnosed in young or middle-aged women with psychopathological disturbances. We reviewed all the cases seen at our Institution over a 24-yr period, from 1973 to 1996. All 25 patients were women. Analysis was restricted to 17 patients who were born and lived in Tuscany (our region), since only these patients were distributed during the whole observation period. Diagnosis of thyrotoxicosis factitia was based on the following parameters: elevated serum total and/or free thyroid hormone levels, undetectable serum thyrotropin levels, low/undetectable serum thyroglobulin concentration, normal urinary iodine excretion, low/suppressed thyroidal radioactive iodine uptake (RAIU), absence of goiter, absence of circulating anti-thyroid antibodies. Surreptitious ingestion of thyroid hormone pill was eventually admitted by all patients. Age at diagnosis was >50 yr in 7/17 patients (41%): 6 of them were distributed in the period 1995-1996, and one in 1988. Patients older than 60 yr were 5/17 (29%), all in the last two years of the period under investigation. There was an increase in the age of patients with thyrotoxicosis factitia (p=0.02), which lost a statistical significance when the patients of the 1995-1996 period were excluded from analysis (p=0.88). This study provides evidence of an increased age of patients with thyrotoxicosis factitia in more recent years. From a practical standpoint, our study suggests that thyrotoxicosis factitia should be suspected and adequately looked for even in old patients with thyrotoxicosis of inexplicable origin, especially in the absence of goiter and thyroid autoimmune phenomena, and when common causes of low-RAIU hyperthyroidism, such as a load with iodine-containing drugs or subacute thyroiditis, have been excluded.

Syndromes of thyrotoxicosis with low radioactive iodine uptake

It is very important to diagnose correctly the etiology of thyrotoxicosis, because the course and treatment of thyrotoxicosis with low radioactive iodine uptake differ significantly from that of hyperthyroidism due to Graves' disease or toxic nodular goiter. Many causes of subacute thyroiditis have been identified producing a characteristic course of transient hyperthyroidism, followed by hypothyroidism, and usually recovery. Ectopic hyperthyroidism includes factitious thyroid hormone ingestion, struma ovarii, and, rarely, large deposits of functioning thyroid cancer metastases. Iodine-induced hyperthyroidism may be associated with low radioiodine uptakes. Amiodarone-associated hyperthyroidism may be the result of subacute thyroiditis or iodine-induced hyperthyroidism; assessment and treatment can be quite challenging.

Rational use of thyroid function tests

In this era of cost containment, it is necessary to efficiently select the most important laboratory investigations for diagnostic and management purposes, with patient benefit as the ultimate objective. Thyroid function tests collectively represent a very costly item for laboratory services and have tended to be unselectively overutilized virtually until the present. Tests available for thyroid function testing include both in vitro and in vivo tests. Virtually all physicians are familiar with the free thyroxine (fT4) or its equivalents (fT4E), total and free triiodothyronine (TT3 and fT3), and sensitive thyrotrophin (TSH) assays, to which may be added plasma thyroglobulin (Tg), and thyroid autoantibodies (TAb) (including thyroid stimulating antibody [TSAb]). In vitro tests include thyroidal uptakes and scans, as well as other imaging techniques (e.g., ultrasound). Other less commonly used or obsolete techniques are not discussed. For screening or case finding where there is little probability that the patient(s) has thyroid dysfunction, a sensitive TSH assay is all that is initially required. If, however, the TSH result is elevated, a fT4E and TAb should then be performed. If the TSH is subnormal, then a fT4E, TT3, and (if still necessary) TSH response to TRH would determine if that patient was truly hyperthyroid (in elderly patients, a low TSH is often not associated with hyperthyroidism!). Conversely, not all patients with elevated fT4 are truly hyperthyroid. Uptakes and scans are primarily of importance in the correct diagnosis of unusual cases of hyperthyroidism and for nodular disease. When patients already diagnosed are being followed, proper selection of testing is again important, sometimes emphasizing one test over others (e.g., TT3); for example, in patients with Graves' Disease on anti-thyroid drugs, the fT4E and TSH values may not reflect the true status of the patient. On the one hand, the TSH may remain low for months after the patient has become euthyroid, and on the other hand, the fT4E may drop even below normal, whereas the T3 remains elevated (and the patient still hyperthyroid). The many other vagaries of these tests are also mentioned.

Color flow Doppler sonography in thyrotoxicosis factitia

Color flow doppler sonography (CFDS) is a powerful technique which displays tissue blood flow and vascularity. Hyperthyroidism due to Graves' disease is characterized by variable degrees of increased blood flow at CFDS. The purpose of this study was to evaluate CFDS patterns in five women with thyrotoxicosis factitia, a condition due to surreptitious ingestion of excess thyroid hormone. Diagnosis was supported by the finding of elevated free thyroxine (FT4), ranging 24.2-67.6 pmol/L (normal values: 8.3-20.5), elevated free triiodothyronine (FT3), ranging 9.9-26.7 pmol/L (normal values: 3.8-8.4), undetectable thyrotropin (TSH), absent anti-thyroid antibodies, undetectable serum thyroglobulin (Tg) concentrations, very low/suppressed thyroidal radioiodine uptake and normal/low urinary iodine excretion. Moreover, all patients admitted thyroid hormone pills intake. All patients had normal thyroid volume and echogenicity at conventional sonography (mean estimated volume, 9.4 ml, range, 6-11 ml), and absent hypervascularity or minimal intrathyroidal vascular spots at CFDS. The peak systolic velocity (PSV) was at the lower limit of normal values (mean, 4 cm/sec, range 3-5 cm/sec). Twenty-six women with untreated Graves' disease had an increase in the mean PSV, (mean 12.9 cm/sec, range 8-20, p < 0.001) and diffuse hypervascularity. CFDS pattern in 24 normal women residing in the same area did not differ from that found in patients with thyrotoxicosis factitia. Thus, due to the nonthyroidal origin of excess thyroid hormone, CFDS showed absent hypervascularity and normal PSV in spite of a thyrotoxic status. These findings well correlate with the etiology of thyrotoxicosis factitia and may represent an additional, useful tool to confirm the diagnosis. For its easiness, rapidity (10 min) and noninvasive features, CFDS can be considered a first line test during office examination when thyrotoxicosis factitia is suspected.

Ablation of thyroid function with radioactive iodine after recurrent episodes of silent thyroiditis

We report the history of a 44-year-old woman, who had four episodes of thyrotoxicosis in 4 years. The clinical findings and laboratory results were all indicative of recurrent silent thyroiditis. Because silent thyroiditis is self-limiting, treatment is usually symptomatic. In this patient radioiodine therapy was eventually prescribed to obviate further recurrences. We were unable to find reports of this number of recurrences.

The measurement of fecal thyroxine in the diagnosis of thyrotoxicosis factitia

Two patients with prolonged thyrotoxicosis are presented with low radioiodide uptake, low-normal serum thyroglobulin concentrations, and low iodide content of the neck on x-ray fluorescence studies. The surreptitious intake of thyroid hormone was directly proven by a high fecal concentration of T4 (12.38 and 23.99 nmol/g) compared with low concentrations in healthy subjects (1.03 +/- 0.64 nmol/g; mean +/- SD, n = 6) and in patients with hyperthyroidism due to Graves' disease (1.93 +/- 1.86; n = 8). Fecal thyroid hormone measurement may help to provide formal proof of factitious thyrotoxicosis.

Occupational thyroid disease

A case of thyrotoxicosis due to the occupational exposure to cosmetics in a 35-year-old beautician is reported. The hormonal pattern was consistent with exogenous thyroid hormone administration, but not with iodine hyperthyroidism. The patient denied she was using thyroid hormones; also, she lacked the typical features of patients with thyrotoxicosis factitia. Her occupational history was carefully reviewed: A heavy exposure of the unprotected skin to cosmetic creams containing iodine, thyroid hormones, and thyroid extracts had occurred in the previous months. The patient was advised to refrain from the exposure, and a persistent remission of thyrotoxicosis was observed thereafter. This case suggests that percutaneous absorption of thyromimetic substances though never described before, may occur in an occupational setting. We advise that such cosmetics be handled with care, not only by patients with thyroid disease but by euthyroid subjects as well; close medical surveillance over the use of such preparations seems appropriate.

Graves' disease. Current concepts

Graves' disease is an organ-specific autoimmune disorder. There is no universal agreement on the mechanism of Graves' disease, but the over-activity of the thyroid is due to an antibody capable of attaching to and activating the TSH receptor of follicular cells. There are other extrathyroidal features that are not caused either by this antibody or by hyperthyroidism. The clinical diagnosis is generally straightforward and can be confirmed by in vitro measurement of thyroid hormones and TSH. A measurement of radioiodine uptake is also valuable. Treatment is not specific for the immunologic defect, but its purpose is to lower the thyroid hormone levels to normal. This can be achieved with antithyroid medication, radioiodine iodine-131, or thyroidectomy. In most clinical situations, a strong argument can be made for iodine-131 therapy, which is safe and definitive, although posttreatment hypothyroidism and the need for lifelong thyroxine are to be expected.

Iodine-induced subacute thyroiditis with thyrotoxicosis presenting as fever of unknown origin

A 26-year-old woman with features of bulimia nervosa presented with fever of unknown origin, hepatomegaly, marked leukocytosis, and increased erythrocyte sedimentation rate. Following prolonged observation, slight tenderness over the thyroid gland and signs of thyrotoxicosis occurred. A thyroid scan demonstrated no isotope uptake and the patient admitted abusing an organic iodine preparation in order to control her weight. The diagnosis of iodine-induced subacute thyroiditis with thyrotoxicosis was, therefore, considered. A brief course of low-dose steroids normalized both thyroid function and hematological parameters. On followup evaluation, urinary iodine excretion and thyroid function tests were normal.

Therapeutic potential of two over-the-counter thyroid hormone preparations

Various brands of over-the counter (OTC) exogenous thyroid hormones are available in health food stores and retail pharmacies. Two commercially available OTC thyroid products were analyzed for total thyroxine (T4) and triiodothyronine (T3) content. The strength of a liquid thyroid gland extract was unlabeled and that of the solid oral preparation was 45 mg per table. The T4 concentration of the liquid preparation was less than 10 micrograms/dL; that of T3 was below the analytical sensitivity of our assay (less than 15 ng/dL). Tablet content of T4 and of T3 was up to 0.5 micrograms and up to 50 ng, respectively. Preliminary data on these OTC thyroid gland extracts cannot be extrapolated to all OTC thyroid products, but they suggest that such products generally contain concentrations of T4 and T3 below clinical effectiveness. Further analytical study is warranted.