2017 Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and the Postpartum

BACKGROUND

Thyroid disease in pregnancy is a common clinical problem. Since the guidelines for the management of these disorders by the American Thyroid Association (ATA) were first published in 2011, significant clinical and scientific advances have occurred in the field. The aim of these guidelines is to inform clinicians, patients, researchers, and health policy makers on published evidence relating to the diagnosis and management of thyroid disease in women during pregnancy, preconception, and the postpartum period.

METHODS

The specific clinical questions addressed in these guidelines were based on prior versions of the guidelines, stakeholder input, and input of task force members. Task force panel members were educated on knowledge synthesis methods, including electronic database searching, review and selection of relevant citations, and critical appraisal of selected studies. Published English language articles were eligible for inclusion. The American College of Physicians Guideline Grading System was used for critical appraisal of evidence and grading strength of recommendations. The guideline task force had complete editorial independence from the ATA. Competing interests of guideline task force members were regularly updated, managed, and communicated to the ATA and task force members.

RESULTS

The revised guidelines for the management of thyroid disease in pregnancy include recommendations regarding the interpretation of thyroid function tests in pregnancy, iodine nutrition, thyroid autoantibodies and pregnancy complications, thyroid considerations in infertile women, hypothyroidism in pregnancy, thyrotoxicosis in pregnancy, thyroid nodules and cancer in pregnant women, fetal and neonatal considerations, thyroid disease and lactation, screening for thyroid dysfunction in pregnancy, and directions for future research.

CONCLUSIONS

We have developed evidence-based recommendations to inform clinical decision-making in the management of thyroid disease in pregnant and postpartum women. While all care must be individualized, such recommendations provide, in our opinion, optimal care paradigms for patients with these disorders.

Fetal/Neonatal Thyrotoxicosis in a Newborn From a Hypothyroid Woman With Hashimoto Thyroiditis

CONTEXT

Fetal/neonatal thyrotoxicosis is a rare but potentially life-threatening condition. It is most commonly observed in poorly controlled Graves disease during pregnancy.

CASE DESCRIPTION

Here we describe a fetus/newborn patient with thyrotoxicosis who was born of a woman with Hashimoto thyroiditis and levothyroxine-treated hypothyroidism. Transplacental passage of stimulating thyrotropin (TSH) receptor antibodies, which were measured by a cell-based bioassay, was the underlying mechanism of fetal/neonatal thyrotoxicosis, although the mother had no history of hyperthyroidism.

CONCLUSION

Diagnosis and management of fetal hyperthyroidism can be challenging. TSH receptor antibody testing should be considered in pregnant women with any history of autoimmune thyroid disease and symptoms of fetal hyperthyroidism.

Thyrotoxicosis Presenting as Unilateral Drop Foot

Neuromuscular disorders associated with hyperthyroidism have several variations in their clinical phenotype, such as ophthalmopathy, periodic paralysis, and thyrotoxic myopathy. We herein report an unusual case of thyrotoxic myopathy presenting as unilateral drop foot. Histopathological examinations of the left tibialis anterior muscle showed marked variation in the fiber size, mild inflammatory cell infiltration, and necrotic and regenerated muscle fibers with predominantly type 1 fiber atrophy. Medical treatment with propylthiouracil resulted in complete improvement of the left drop foot. This case expands the phenotype of thyrotoxicosis and suggests that thyrotoxicosis be considered as a possible cause of unilateral drop foot.

Partial prediction of postpartum Graves' thyrotoxicosis by sensitive bioassay for thyroid-stimulating antibody measured in early pregnancy

Graves' disease often occurs after delivery. However, it has been difficult to predict who will develop Graves' hyperthyroidism. We attempted to predict postpartum onset of Graves' disease by measuring anti-TSH receptor antibodies (TRAb) and thyroid-stimulating antibodies (TSAb) in early pregnancy. TRAb was measured by a third generation assay and TSAb was measured by a newly developed sensitive bioassay. In 690 early pregnant women, 2 showed borderline TRAb positive reactions. However, none of them developed Graves' disease after delivery. Thirty-eight of 690 pregnant women were positive for anti-thyroid peroxidase antibodies (TPOAb) and 4 were positive for TSAb. Two of these 4 women developed postpartum Graves' hyperthyroidism. These findings indicate that the third generation TRAb assay was not useful, but that the sensitive TSAb bioassay was moderately useful for predicting the postpartum onset of Graves' hyperthyroidism.

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.

Thyrotoxicosis presenting as hypokalaemic paralysis and hyperlactataemia in an oriental man

A 35-year-old Malaysian man presented with rapid onset of flaccid quadriparesis associated with nausea and vomiting. General blood tests revealed severe hypokalaemia (serum potassium 1.5 mmol/L) and hypophosphataemia (serum phosphate 0.29 mmol/L) as a potential cause of the flaccid paralysis. Arterial blood gases showed mixed acid base disturbance of respiratory alkalosis and metabolic acidosis with hyperlactataemia. Thyrotoxic periodic paralysis (TPP) was suspected as the underlying cause of this presentation and thyroid function tests showed severe hyperthyroid results (free T4 > 77.2 pmol/L, free T3 19.3 pmol/L, thyroid-stimulating hormone [TSH] < 0.05 mIU/L). Treatment with intravenous potassium and phosphate infusion and oral propranolol resulted in rapid resolution of his symptoms. A discussion of the clinical and pathophysiological features and treatment of TPP (a very rare encounter in UK clinical practice) is presented, and to our knowledge associated hyperlactataemia has not been previously described.

Hyperthyroidism

Hyperthyroidism is characterised by increased thyroid hormone synthesis and secretion from the thyroid gland, whereas thyrotoxicosis refers to the clinical syndrome of excess circulating thyroid hormones, irrespective of the source. The most common cause of hyperthyroidism is Graves' disease, followed by toxic nodular goitre. Other important causes of thyrotoxicosis include thyroiditis, iodine-induced and drug-induced thyroid dysfunction, and factitious ingestion of excess thyroid hormones. Treatment options for Graves' disease include antithyroid drugs, radioactive iodine therapy, and surgery, whereas antithyroid drugs are not generally used long term in toxic nodular goitre, because of the high relapse rate of thyrotoxicosis after discontinuation. β blockers are used in symptomatic thyrotoxicosis, and might be the only treatment needed for thyrotoxicosis not caused by excessive production and release of the thyroid hormones. Thyroid storm and hyperthyroidism in pregnancy and during the post-partum period are special circumstances that need careful assessment and treatment.

The presence of anti-thyroglobulin (TgAb) and/or anti-thyroperoxidase antibodies (TPOAb) does not exclude the diagnosis of type 2 amiodarone-induced thyrotoxicosis

PURPOSE

It is widely accepted that type 2 amiodarone-induced thyrotoxicosis (AIT) generally occurs in patients with a normal thyroid gland without signs of thyroid autoimmunity. However, it is currently unknown if the presence of anti-thyroglobulin (TgAb) and/or anti-thyroperoxidase antibodies (TPOAb) in AIT patients without other signs of an underlying thyroid disease may impair the response to glucocorticoid therapy.

METHODS

We performed a pilot retrospective cohort study with matched-subject design and an equivalence hypothesis, comparing the response to glucocorticoid therapy between 20 AIT patients with a normal thyroid gland, low radioiodine uptake, undetectable TSH receptor antibodies and positive TgAb and/or TPOAb (Ab+ group), and 40 patients with the same features and absent thyroid antibodies (Ab- group).

RESULTS

The mean cure time was 54 ± 68 days in the Ab+ group and 55 ± 49 days in the Ab- group (p = 0.63). The equivalence test revealed an equivalent cure rate after 60, 90 and 180 days (p = 0.67, 0.88 and 0.278, respectively). The occurrence of permanent hypothyroidism was higher in the Ab+ group than in the Ab- group (26.3 vs 5.13 %, p = 0.032).

CONCLUSIONS

The presence of TgAb and/or TPOAb does not affect the response to glucocorticoid therapy, suggesting that the patients with features of destructive form of AIT should be considered as having a type 2 AIT irrespective of the presence of TGAb or TPOAb. These patients have a higher risk of developing hypothyroidism after the resolution of thyrotoxicosis and should be monitored accordingly.

Recurrent Takotsubo Cardiomyopathy Related to Recurrent Thyrotoxicosis

Takotsubo cardiomyopathy, or transient left ventricular apical ballooning syndrome, is characterized by acute left ventricular dysfunction caused by transient wall-motion abnormalities of the left ventricular apex and mid ventricle in the absence of obstructive coronary artery disease. Recurrent episodes are rare but have been reported, and several cases of takotsubo cardiomyopathy have been described in the presence of hyperthyroidism. We report the case of a 55-year-old woman who had recurrent takotsubo cardiomyopathy, documented by repeat coronary angiography and evaluations of left ventricular function, in the presence of recurrent hyperthyroidism related to Graves disease. After both episodes, the patient's left ventricular function returned to normal when her thyroid function normalized. These findings suggest a possible role of thyroid-hormone excess in the pathophysiology of some patients who have takotsubo cardiomyopathy.

Clinical Features and Surgical Treatment of Thyroid Pathology in Patients Over 65 Years

INTRODUCTION

The significant increase in the average lifespan of the general population lead to a proportional enhacement in the prevalence of benign and malignant thyroid conditions and equally the number of surgeries for this pathology.

PATIENTS AND METHOD

In a personal series of 464 thyroid disorders undergoing surgery over a two decades period we registered 51 patients (10.9%) aged over 65 years of which 11 (2.4%) having over 75 years. Demographic, clinical and diagnostic characteristics of these cases were analysed together with indications, management practice and outcome. Retrospective statistical analysis reaearching risk factor and confidence interval has not identified factors predicting higher risk of complication in this age group.

RESULTS

There have been recorded 33 females and 18 males (R1=1,8/1) with clinically, laboratory and histologically confirmed diagnosis of 24 (multi)nodular goiters (47.0%), 18 thyrotoxicosis (35.2%) and also 9 (17.6%) thyroid carcinomas. Thirty-four total or near total thyroidectomies and 17 conservative exeresis were performed. There were not postoperative deaths but we recorded three cases of prolonged hypocalcemia, and two cases each of recurrent laryngeal nerve paresis and recurrences. In all benign cases we obtained a stable in time cure while in carcinomas survivals of 3-5 years were obtained in only 4 papillary tumors.

CONCLUSIONS

Despite some difficulties in diagnostic and additional risks related to comorbidity benign and malignant pathology installed in patients over 65 years, may benefit of all types of conservative or radical thyroidectomies in terms of strict monitoring individualized in each case.

Onset of ulcerative colitis after thyrotoxicosis: a case report and review of the literature

OBJECTIVE

Ulcerative colitis is a chronic disease that could be triggered by acute stressful events, such as gastrointestinal infections or emotional stress.

PATIENTS AND METHODS

We reported the case of the onset of an ulcerative colitis after a thyrotoxicosis crisis and reviewed the literature about the relationships between thyroid dysfunctions and ulcerative colitis.

RESULTS

A 38-year-old woman was diagnosed with ulcerative colitis after her third thyrotoxicosis crisis, two years after the diagnosis of Graves' disease. In this case, thyrotoxicosis acted as a trigger for ulcerative colitis onset.

CONCLUSIONS

Hyperthyroidism could be a trigger able to elicit ulcerative colitis in susceptible patients.

Postpartum thyroid dysfunction in women with autoimmune thyroiditis

INTRODUCTION

Autoimmune thyroiditis (AIT) is a predisposing factor for developing postpartum thyroid dysfunction (PPTD).

AIM

To study the characteristics of PPTD in women with AIT.

METHODS

Thirty-eight women with pre-existing AIT were included in the study. Thyroid-stimulating hormone, free triiodthyronine, free thyroxine, thyroid peroxidase antibodies, thyroglobulin antibodies were measured and ultrasound evaluation of the thyroid gland was performed in the first trimester of pregnancy and during the first year following delivery.

RESULTS

Thyroid dysfunction was recognized in 68.4% of the patients - 28.9% presented with hypothyroidism and 39.5 % with thyrotoxicosis. The immunological and morphological parameters did not differ between euthyroid women and those with thyroid dysfunction. At the end of the postpartum period restoration of euthyroid state (being on the treatment before pregnancy) was observed in 15.4% of patients with PPTD, while 84.6% required increase of the levothyroxine dose. The analysis found a significantly lower volume of the thyroid gland, shorter duration of the disease, a lower dose of levothyroxine before and during gestation in patients with impaired thyroid function at the end of the postpartum period.

CONCLUSION

The risk of PPTD in women with AIT predating pregnancy is higher among women with preserved thyroid functional capacity motivating a thorough assessment of thyroid hormone levels and close follow-up of those women during the postpartum period.

An Unusual Case of Acute Muscle Weakness

A previously healthy 35-year old man presented to hospital with acute leg weakness following an alcohol binge. On assessment, tachycardia, urinary retention and bilateral upper and lower limb proximal weakness with preserved peripheral power were noted. Biochemistry revealed marked hypokalaemia, which responded to intravenous replacement, and biochemical thyrotoxicosis, leading to the diagnosis of Thyrotoxic Periodic Paralysis (TPP). Anti-thyroid therapy and beta-blockers were commenced and his neurological symptomatology resolved as he became progressively euthyroid. TPP is a rare acquired subtype of hypokalaemic periodic paralysis, typically causing proximal muscle weakness associated with thyrotoxicosis. It is most common in young Asian males. Acute treatment requires cautious oral potassium supplementation, beta-blockade, and anti-thyroid therapy. TPP is prevented by maintaining euthyroidism; otherwise recurrence is likely.

PREGNANCY, THYROTOXICOSIS AND POLYMYOSITIS

A young pregnant lady of 26 years age, presented with recent onset weaKness of legs. On examination, she was only able to move legs from side to side and lift the arms with difficulty. Rest of neurological and systemic examination did not reveal any abnormality. On investigations, there were raised serum muscle enzyme levels, hyperthyroid hormone profile, myopathy on electromyography and myositis on muscle biopsy. Common conditions of myositis were excluded. She was given glucocorticoids and methimazole to which she responded well.

Anginalike pain and normal coronary arteries

Atherosclerotic CAD is the most common cause of cardiac chest pain in Western countries. Other cardiac syndromes may also cause anginalike pain and may be difficult to differentiate from atherosclerotic CAD. It is essential to make this distinction, because management and prognosis of these conditions are entirely different. A detailed history and, in some cases, special diagnostic methods can help make the diagnosis. When evaluating patients with anginalike chest pain and normal coronary arteries, physicians need to consider this group of diseases and tailor workup and diagnosis on an individual basis.

Neonatal thyrotoxicosis with severe supraventricular tachycardia: case report and review of the literature

Neonatal thyrotoxicosis is a rare condition caused by the transplacental passage of thyroid stimulating immunoglobulins from mothers with Graves' disease. We report a case of neonatal thyrotoxicosis with concurrent supraventricular tachycardia (SVT). The female infant, who was born by section due to breech delivery and meconium in the amniotic fluid at 36 weeks of gestation, presented with tachycardia on day 7. Her heart rate was between 260 and 300 beats/min, and an electrocardiogram revealed ongoing SVT. Sotalol was effective after two cardioversions in maintaining sinus rhythm. Thyroid function studies revealed hyperthyroidism in the infant, and her mother was found to have Graves' disease. Since symptoms and signs can vary, especially in preterm infants with neonatal hyperthyroidism, we want to emphasize the importance of prenatal care and follow-ups of Graves' disease associated pregnancies and management of newborns after birth.

Serum human chorionic gonadotropin levels and thyroid hormone levels in gestational transient thyrotoxicosis: Is the serum hCG level useful for differentiating between active Graves' disease and GTT?

Gestational transient thyrotoxicosis (GTT) is defined as transient thyrotoxicosis caused by the stimulating effect of human chorionic gonadotropin (hCG) during pregnancy. We attempted to identify the serum hCG level that causes GTT, and we compared the serum hCG levels and thyroid hormone levels of GTT patients according to whether they had a background of thyroid disease. We also evaluated serum hCG as a parameter for differentiating between active Graves' disease (GD) and GTT. We reviewed the 135 cases of pregnant women who came to our hospital to be evaluated for thyrotoxicosis during their 7th to 14th week of pregnancy, and their serum hCG level was measured at that time. Among the 135 pregnant women with thyrotoxicosis; 103 of the women had GTT, and the other 32 women had active GD. There were no correlations between their serum hCG levels and free thyroid hormone levels. There were no significant differences in thyroid hormone levels or hCG levels among the GTT groups with different thyroid disease backgrounds; i.e., the GTT group without thyroid disease, GTT group with chronic thyroiditis, GTT group with non-functioning thyroid nodules, and GTT group with GD in remission. The serum hCG level of the GTT group was significantly higher than in the active GD group, but it was not a good parameter for differentiating between the two groups. The FT3/FT4 ratio of the active GD was significantly higher than in GTT group, and was a better parameter for differentiation.

Sunitinib-induced thyrotoxicosis - a not so rare entity

BACKGROUND/AIM

The tyrosine kinase inhibitor (TKI) sunitinib malate is nowadays a standard first-line treatment option for patients with metastatic clear-cell renal cell carcinoma (mRCC). The aim of this study was to evaluate the incidence and clinical course of thyrotoxicosis in our cohort of patients treated with sunitinib.

PATIENTS AND METHODS

Medical records of all patients treated with first-line sunitinib for mRCC at our Institution between November 2008 and March 2014 were retrospectively reviewed. Thyroid function was assessed after every 2 cycles of therapy, during the 2 weeks off period.

RESULTS

Out of the 62 included patients, hypothyroidism has developed during therapy in 12 patients (19%) and it was preceded by thyrotoxicosis in 2 (3.2%).

CONCLUSION

Sunitinib-induced thyrotoxicosis (SIT), a not so rare entity, was followed by hypothyroidism. The patterns of occurrence and possible significance of SIT, as predictive marker of better treatment response to sunitinib, need to be validated in further studies.

Thyrotoxic, hypokalemic periodic paralysis (THPP) in adolescents

INTRODUCTION

Periodic paralysis associated with hyperthyroidism and hypokalemia is an uncommon disorder reported primarily in Asian males and rarely in children. We report three Hispanic adolescent males who were seen with Graves' disease (GD) and THPP.

METHODS

The method used was chart review.

RESULTS

Two of these boys presented with episodes of paralysis and were diagnosed with GD. The third was initially seen with hyperthyroidism and developed weakness and paralysis when his disease progressed because of therapeutic noncompliance. Hypokalemia was documented in two of the three patients with the third not seen during paralysis. Intravenous K⁺ was required in only one case. All three boys were treated with antithyroid medications and β blockers, and the musculoskeletal symptoms resolved in all three when hyperthyroidism was controlled after 2 weeks of treatment. The duration for each episode of weakness and paralysis varied in each case and resolved within 15 min to 2 h in case 1, 1-5 h in case 2, and 24 h in case 3.

CONCLUSIONS

THPP is considered uncommon except in Asian males and rare in childhood and adolescence. Its occurrence in these three Hispanic boys suggests that it may occur more frequently in the young and in the USA than has been suspected, especially with the changing national demographics. We believe that our experience should raise the awareness of THPP among pediatric care providers.

[Apathetic hyperthyroidism with heart failure in an elderly patient with Plummer's disease]

We report a case of apathetic hyperthyroidism associated with unrecognized slowly growing functional thyroid adenoma (Plummer's disease), atrial fibrillation and heart failure. An 81-year-old woman with worsening thyroid dysfunction was admitted to our hospital for the treatment of heart failure. The patient had developed heart failure associated with chronic atrial fibrillation at 76 years of age, and one year later was found to have asymptomatic hyperthyroidism. Anti-thyroid autoantibodies were negative, but thyroid echography showed a 32-mm tumor devoid of internal blood flow in the left lower lobe. Free thyroxine 4 (FT4) decreased from 3.30 to 2.60 ng/dl without treatment. The patient was diagnosed with transient thyroiditis and was followed-up without treatment. However, a repeat thyroid echography showed growth of the tumor to 41 mm in 4 years. Thyroid scintigraphy showed uptake that matched the thyroid mass. Based on these findings, the established diagnosis was Plummer's disease complicated with heart failure. The patient was treated with anti-thyroid drugs, which resulted in improvement of FT4 and reduced the severity of heart failure. In this rare case of an elderly patient, Plummer's disease was associated with a slowly-growing functional thyroid adenoma, apathetic hyperthyroidism, repeated episodes of atrial fibrillation and heart failure. Since symptoms of thyrotoxicosis are likely to be missed in the elderly, it is necessary to include hyperthyroidism in the pathoetiology of heart failure and atrial fibrillation in this population.

Amiodarone-related thyroid dysfunction

Nowadays, amiodarone is the most commonly used antidysrhythmic drug in clinical practice. It is highly effective in the management of recurrent ventricular dysrhythmias, paroxysmal supraventricular dysrhythmias, including atrial fibrillation and flutter, and in the maintenance of sinus rhythm after electrical cardioversion of atrial fibrillation. Moreover, it has the added benefit of being well tolerated in patients with both normal and impaired left ventricular systolic function. Despite amiodarone's potent antidysrhythmic actions, its use is hampered by numerous adverse effects on various organs, including the thyroid. Adverse effects are becoming more prevalent given the increasing incidence of dysrhythmias and wider amiodarone use. Thus, physicians and patients should both be aware of the potential thyroid-specific sequelae. However, amiodarone is likely to remain a significant problem for endocrinologists as concerns exist over the use of the new alternative antiarrhythmic agent, dronedarone, especially in patients with heart failure and left ventricular dysfunction because of the risk of hepatic injury and increased mortality. The final diagnostic and therapeutic approaches must be discussed among the patient, the general practitioner, the cardiologist, and the endocrinologist.

Animal models of disease: feline hyperthyroidism: an animal model for toxic nodular goiter

Since first discovered just 35 years ago, the incidence of spontaneous feline hyperthyroidism has increased dramatically to the extent that it is now one of the most common disorders seen in middle-aged to senior domestic cats. Hyperthyroid cat goiters contain single or multiple autonomously (i.e. TSH-independent) functioning and growing thyroid nodules. Thus, hyperthyroidism in cats is clinically and histologically similar to toxic nodular goiter in humans. The disease in cats is mechanistically different from Graves' disease, because neither the hyperfunction nor growth of these nodules depends on extrathyroidal circulating stimulators. The basic lesion appears to be an excessive intrinsic growth capacity of some thyroid cells, but iodine deficiency, other nutritional goitrogens, or environmental disruptors may play a role in the disease pathogenesis. Clinical features of feline toxic nodular goiter include one or more palpable thyroid nodules, together with signs of hyperthyroidism (e.g. weight loss despite an increased appetite). Diagnosis of feline hyperthyroidism is confirmed by finding the increased serum concentrations of thyroxine and triiodothyronine, undetectable serum TSH concentrations, or increased thyroid uptake of radioiodine. Thyroid scintigraphy demonstrates a heterogeneous pattern of increased radionuclide uptake, most commonly into both thyroid lobes. Treatment options for toxic nodular goiter in cats are similar to that used in humans and include surgical thyroidectomy, radioiodine, and antithyroid drugs. Most authorities agree that ablative therapy with radioiodine is the treatment of choice for most cats with toxic nodular goiter, because the animals are older, and the disease will never go into remission.