Test for recovery from hypothyroidism during thyroxine therapy in Hashimoto's thyroiditis

Clinical Outcomes After Discontinuation of Thyroid Hormone Replacement: A Systematic Review and Meta-Analysis

Background: Levothyroxine (LT4) is one of the most commonly prescribed medications. Although considered a life-long replacement therapy, LT4 therapy can be discontinued for some patients. This study aims at: (i) reviewing the evidence on clinical outcomes of patients undergoing thyroid hormone replacement discontinuation, (ii) identifying the predictors of successful discontinuation, and (iii) systematically appraising frameworks used for deprescribing thyroid hormone. Methods: We searched multiple bibliographic databases, including Ovid MEDLINE(R) and Epub Ahead of Print, In-Process & Other Non-Indexed Citations and Daily, Ovid Embase, Ovid Cochrane Central Register of Controlled Trials, Ovid Cochrane Database of Systematic Reviews, and Scopus, from inception to February 2020 for studies in which thyroid hormone replacement was discontinued. Clinical outcomes assessed included: proportion of patients that remained euthyroid or needed to restart thyroid hormone replacement after discontinuation and frequency of clinical symptoms of hypothyroidism and adverse effects. We also evaluated predictors for discontinuation and deprescribing frameworks. Reviewers (F.J.K.T., N.B., N.M.S.O., S.M.) evaluated studies for inclusion, extracted data, and assessed methodological quality independently and in duplicate. Results: Seventeen observational studies at moderate to high risk of bias met inclusion criteria, including a total of 1103 patients (86% women) with an age range of 2-81 years. Approximately a third of patients undergoing thyroid hormone discontinuation remained euthyroid at follow-up (37.2%, 95% confidence interval [CI 24.2-50.1%], I² 97.5%). Subgroup analysis showed that patients with a previous diagnosis of overt hypothyroidism (OH) were less likely to remain euthyroid (11.8% [CI 0.4-23.2%], I² 90.3%) than patients with a prior diagnosis of subclinical hypothyroidism (SCH) (35.6% [CI 8.2-62.9%], I² 94.0%). No study followed a framework for systematically deprescribing LT4. Conclusions: Low-quality evidence suggests that up to a third of patients remained euthyroid after thyroid hormone discontinuation, with a higher proportion of patients with an initial diagnosis of SCH remaining euthyroid than patients with an initial diagnosis of OH. A deprescribing framework focusing on adequate selection of patients for deprescribing LT4 and a systematic process is warranted to guide clinicians in re-evaluating the need for LT4 in their patients.

Clinical factors predicting the successful discontinuation of hormone replacement therapy in patients diagnosed with primary hypothyroidism

BACKGROUND

Although reversible in some patients, primary hypothyroidism is considered a permanent condition requiring lifelong hormone therapy. This study aimed to investigate the factors predicting the successful discontinuation of levothyroxine (L-T4) therapy in patients with primary hypothyroidism.

METHODS

A retrospective study was performed in primary hypothyroidism patients who met inclusion criteria: patients who maintained stable L-T4 therapy for more than 1 year, following gradual dose reduction of L-T4 based on the clinical decision (L-T4 tapering); patients receiving either no L-T4 or a fixed minimum dose for more than 1 year after L-T4 tapering. Reduction in L-T4 dosage by 12.5-50 μg within 3 months was considered as L-T4 tapering. Serum free T4, TSH, and clinical symptoms were evaluated before, during and after tapering. Logistic regression and decision tree analyses were performed to predict the successful discontinuation of L-T4.

RESULTS

Among 382 patients, 22.5% and 58.4% showed successful discontinuation (T4-Discontinued) and dose reduction (T4-Reduced) of L-T4 therapy, while other did not obtained any reduction of L-T4 dose (T4-Unchanged). The median number of tapering visit was 1.0 (range, 1.0-4.0). In T4-Discontinued group, the TSH level and the positive rate of anti-thyroperoxidase at the time of L-T4 initiation were lower, the duration of L-T4 therapy was shorter, and the maintenance dose of L-T4 at the time of tapering was lower than those in the T4-Unchanged group. In ultrasonography, normal parenchyma was preserved in the T4-Discontinued group while others showed higher rates of heterogeneous or hypoechoic parenchymal changes. Among those different characteristics, the longer duration of L-T4 therapy and the higher maintenance dose of L-T4 at the time of tapering significantly predicted the failure of discontinuation of L-T4 in multivariate analysis. A decision tree showed that patients with a duration of L-T4 therapy >4.6 years had lower success rate of discontinuation.

CONCLUSION

Shorter duration of L-T4 therapy and lower L-T4 dose at the time of tapering are the predictable factors for successful L-T4 tapering in stably maintained primary hypothyroidism patients.

Hypothesis: Persistently normal TSH levels may be used to recognize patients with transient forms of hypothyroidism and to suggest treatment withdrawal

There are no text-book recommendations on when or if treatment should or could be stopped in patients with a diagnosis of hypothyroidism, and these patients usually receive lifelong thyroxine therapy (despite the fact that some of them may have forms of transient hypothyroidism that will later recover function). Since TSH fluctuations during thyroxine treatment are common and a lack of this fluctuation might be used to identify patients who no longer need thyroxine treatment, we hypothesize that by offering patients with persistently controlled TSH levels a withdrawal trial of thyroxine treatment we may identify those who no longer need life-long treatment.

Rheumatic and autoimmune thyroid disorders: a causal or casual relationship?

A number of dysfunctions may affect the thyroid gland leading either to hyper- or hypothyroidism which are mediated by autoimmune mechanisms. Thyroid abnormalities may represent an isolated alteration or they may be the harbinger of forthcoming disorders as is the case of well-characterized polyendocrine syndromes. Also, they may precede or follow the appearance of rheumatic manifestations in patients affected with connective tissue diseases or rheumatoid arthritis. The mechanisms by which autoimmune thyroid disorders may be linked to systemic autoimmune diseases have not been fully unraveled yet, however alterations of common pathways are suggested by shared genetic variants affecting autoantigen presentation and regulation of the immune response. On the other hand, the higher prevalence of autoimmune thyroid disorders over rheumatic diseases compels the chance of a mere causal concomitancy in the same patient. The aim of our paper is to provide an overview of available data on thyroid involvement in different rheumatic diseases and to go over the main rheumatic manifestations in the context of autoimmune thyroid diseases.

Case report: rapid spontaneous recovery from severe hypothyroidism in 2 teenage girls

Background

While it is recognized that patients sometimes recover from autoimmune hypothyroidism, little is known about how rapidly this may occur.

Case reports

Two 13 year old girls had severe primary hypothyroidism (total T4 14.2 nmol/L with TSH 468 miU/L and total T4 7.7 nmol/L with TSH 183 miU/L) accompanied by goiter and positive thyroid peroxidase antibodies. There were delays in starting thyroid hormone replacement, and complete reversal of hypothyroidism was documented within 2 months in both cases. One of the girls had recurrence of severe hypothyroidism after being euthyroid for 18 months.

Review of literature

There are few published studies which have looked systematically at reversibility of acquired hypothyroidism, but one Japanese study found that recovery from autoimmune hypothyroidism may occur within weeks. Other causes of primary hypothyroidism (TSH-blocking antibodies, iodine excess, medications) seem less likely, so this probably represents rapid spontaneous reversal of autoimmune hypothyroidism.

Conclusion

Patients with severe autoimmune hypothyroidism may have spontaneous normalization of thyroid tests within weeks to months after diagnosis. This suggests that reevaluating the need for thyroid hormone replacement in selected patients with persistently normal TSH during therapy should be considered.

Does recovery of adrenal function occur in patients with autoimmune Addison's disease?

OBJECTIVE

We earlier discovered partial recovery in a patient with autoimmune Addison's disease. The aim of this study was to assess the occurrence of adrenocortical recovery in patients with autoimmune adrenalitis.

DESIGN

Cross-sectional study.

PATIENTS

Twenty-seven adult patients with autoimmune Addison's disease on stable glucocorticoid and mineralocorticoid replacement therapy (RT) attending the Department of Endocrinology of a university teaching hospital were included in this study.

METHODS

Adrenocortical function was assessed by performing an adrenocorticotrophic hormone (ACTH) (250 μg Synacthen) stimulation test (SST) after interruption of current glucocorticoid and mineralocorticoid RT. A normal adrenal response was defined as a serum cortisol concentration ≥500 nm 30 or 60 min after stimulation. Partial recovery was defined as a cortisol concentration ≥100 and ≤500 nm after stimulation.

RESULTS

In 17 patients (63%), serum cortisol concentrations remained undetectable 30 and 60 min after the administration of ACTH. None of the remaining 10 participants had a normal response. Only one patient reached a cortisol concentration of 100 nm after 60 min, but this could not be confirmed during a second SST.

CONCLUSIONS

In this cross-sectional study among 27 patients with autoimmune adrenalitis, no new cases of adrenocortical recovery were found.

The frequency of Hashimoto thyroiditis in children and the relationship between urinary iodine level and Hashimoto thyroiditis

The aim of this study was to determine the frequency of thyroid autoimmunity in second grade primary school students and to examine the relationship between iodine and Hashimoto thyroiditis (HT). This was a cohort study performed with 1000 students. Urinary iodine levels, antithyroid peroxidase (anti-TPO) and antithyroglobulin (anti-Tg) antibodies were determined in all children. Children with anti-TPO or anti-Tg antibody positivity or with goiter were summoned for detailed examinations. In total, 36 cases (3.6%) were diagnosed as HT. The goiter frequency was found in 17.5% of the whole cohort. Additionally, iodine deficiency was found in 64.2% of all children. The median urinary iodine excretion was determined as 132 microg/L (range 382 microg/L) in the HT group, whereas it was 73 microg/L (range 390 microg/L) in children with goiter but without HT and 81 microg/L (range 394 microg/L) in normal children. The urinary iodine level of HT cases was significantly higher than the other two groups (p < 0.001). HT was also determined in 2% of patients with low urinary iodine levels, in 6.2% of patients with normal urinary iodine levels, and in 7.5% of patients with high urinary iodine levels. Our data demonstrates the close relationship between excessive iodine levels and autoimmunity.

Hashimoto's thyroiditis: TGAb, TPOAb, TRAb and recovery from hypothyroidism

Hashimoto described four patients with goiter. The histology of the goiter was characterized by diffuse lymphocytic infiltration, fibrosis and epithelial cell destruction. Thyroglobulin antibody (TGAb) and thyroid peroxidase antibody (TPOAb) have been used to diagnose Hashimoto's thyroiditis. Patients with positive TGAb and/or TPOAb have been assumed to have Hashimoto's thyroiditis. Approximately 10% of those with positive TGAb and/or TPOAb have hypothyroidism. There are two types of autoimmune thyroiditis: goitrous Hashimoto's thyroiditis and atrophic thyroiditis. The latter patients have blocking antibody (thyroid-stimulating hormone [TSH]-stimulation blocking antibody [TSBAb]). TSBAb is a TSH-receptor antibody (TRAb). TSBAb causes thyroid atrophy and hypothyroidism. TGAb and/or TPOAb do not necessarily cause hypothyroidism. Hypothyroid patients with Hashimoto's thyroiditis usually receive life-long l-thyroxine therapy. However, spontaneous recovery from hypothyroidism has been reported. Patients who had Hashimoto's hypothyroidism and then Graves' hyperthyroidism (and vice versa), have also been reported. Hashimoto's hypothyroidism and Graves' hyperthyroidism could be the opposite spectrums of one disease.

Assessment of thyroid function during the long course of Hashimoto's thyroiditis in children and adolescents

CONTEXT

The prognosis of Hashimoto's thyroiditis (HT) in children and adolescents is not well known and studies reporting long-term outcome of the disease are scarce.

OBJECTIVE

To assess the thyroid hormone status during long-term follow-up and to establish the prognosis of children and adolescents with HT.

PATIENTS

One hundred and twenty-nine patients with HT were re-evaluated for thyroid hormone status after a mean follow-up period of 50 months.

RESULTS

Seventy-seven per cent of the euthyroid patients were still euthyroid, while 21.1% of these patients became hypothyroid at the time of re-evaluation. However, 69.5% of hypothyroid patients remained hypothyroid (overt or subclinical) and 30.5% recovered.

CONCLUSION

HT is a dynamic process. Thyroid functions can show variation during follow-up. Therefore, thyroid function tests should be repeated periodically to detect progression to hypothyroidism in initially euthyroid patients as well as reversibility of hypothyroidism.

The clinical significance of subclinical thyroid dysfunction

Subclinical thyroid disease (SCTD) is defined as serum free T(4) and free T(3) levels within their respective reference ranges in the presence of abnormal serum TSH levels. SCTD is being diagnosed more frequently in clinical practice in young and middle-aged people as well as in the elderly. However, the clinical significance of subclinical thyroid dysfunction is much debated. Subclinical hyper- and hypothyroidism can have repercussions on the cardiovascular system and bone, as well as on other organs and systems. However, the treatment and management of SCTD and population screening are controversial despite the potential risk of progression to overt disease, and there is no consensus on the thyroid hormone and thyrotropin cutoff values at which treatment should be contemplated. Opinions differ regarding tissue effects, symptoms, signs, and cardiovascular risk. Here, we critically review the data on the prevalence and progression of SCTD, its tissue effects, and its prognostic implications. We also examine the mechanisms underlying tissue alterations in SCTD and the effects of replacement therapy on progression and tissue parameters. Lastly, we address the issue of the need to treat slight thyroid hormone deficiency or excess in relation to the patient's age.

Role of fine needle aspiration cytology in thyroiditis

Fine needle aspiration (FNA) of thyroid is a cost-effective, simple, diagnostic tool in the initial screening of patients with thyroid lesions. Its role in a minimally enlarged thyroid in a symptomatic patient suspected of thyroid dysfunction is now well known. It plays an important role in the medical management of all nonpalpable/minimally enlarged thyroid (goiter) in patients suspect for thyroid pathology and/or in combination with thyroid-stimulating hormone, T3 and T4 levels by diagnosing early cases of thyroiditis. FNA may be of assistance in the early detection of subclinical hypothyroidism, which is of utmost importance in pregnant women, and further makes possible the availability of baseline values for future reference. With the implementation of this protocol of FNA thyroid with/without imaging, we affirm that the practice of cytology has differed in different geographic areas and from country to country, depending on economy and availability of infrastructure.

Autoimmune thyroid disease with fluctuating thyroid function

The authors describe the case of a woman with autoimmune thyroid disease, who presented with hypothyroidism but went on to develop hyperthyroidism.

Chronic autoimmune thyroiditis and rheumatic manifestations

A variety of rheumatic manifestations have been described in association with autoimmune thyroiditis. In the past, most of these manifestations were attributed to the underlying thyroid dysfunction, in particular hypothyroidism. However, a responsibility of the mechanisms involved in the autoimmunity rather than a direct action of thyroid hormones seems supported by the evidences that some rheumatic manifestations may occur even in euthyroid patients, or that they are more frequent in hypothyroid patient with autoimmune thyroiditis than in those without this disease. Rheumatic manifestations could be sometimes attributable to the autoimmune rheumatic diseases frequently associated with autoimmune thyroiditis, such as Sjögren's syndrome, rheumatoid arthritis, systemic lupus erythematosus, or scleroderma. Among the most important or frequent rheumatic manifestations there are a mild non-erosive variety of arthritis, polyarthralgia, myalgia, and sicca syndrome without a true Sjögren's syndrome. Although the possible pathogenesis of these manifestations is not completely established, some hypotheses may be proposed, including a role of autoantibodies characteristics of autoimmune thyroiditis, a possible overlap between autoimmune thyroiditis and some autoimmune rheumatic diseases, and a systemic inflammatory reaction associated with thyroiditis.

Clinical manifestations and outcome of polyarthralgia associated with chronic lymphocytic thyroiditis

OBJECTIVES

Arthralgia is among the most frequent musculoskeletal symptoms occurring in patients with chronic lymphocytic thyroiditis (CLT), often causing pain and physical impairment over extended periods of time. Our study aims to characterize arthralgia and, in particular, polyarthralgia (PA) associated with CLT and to evaluate the influence of thyroid replacement therapy.

METHODS

Of 130 patients affected with CLT attending the Division of Rheumatology for rheumatic complaints, the authors sequentially selected 20 patients with PA without any known rheumatic diseases. Of these 20 patients, 8 were euthyroid, 2 hyperthyroid, and 10 hypothyroid. The last group had never undergone therapy for thyroid disease; then, they were treated with thyroxine and followed up for 24 months. Clinical assessment included the number of joints affected by pain (NAJ), the visual analogic scale of pain (VAS), the duration of PA (number of days), and the intake of acetaminophen.

RESULTS

At baseline, the only correlations in the 20 patients with PA were between NAJ and antithyroid microsomal antibodies (r =.782; P <.001), thyroid stimulation hormone (r =.651; P =.001), and erythrocyte sedimentation rate (r =.511; P = 0.021), respectively. During follow-up, although symptoms improved in the 10 hypothyroid patients treated with thyroxine, a statistical significance was reached only after 12 months.

CONCLUSIONS

Patients with CLT may be affected with PA severely, even in absence of hypothyroidism. Replacement therapy with thyroxine in hypothyroid patients with CLT induced a progressive but gradual improvement of symptoms.

Thyroid ultrasound

Evaluation of the thyroid gland can be performed by several imaging techniques. Although ultrasound (US) lacks specificity for tissue diagnosis and can rarely distinguish benign from malignant disease, it can distinguish solid nodules from simple and complex cysts. It allows accurate estimation of thyroid size, gives a rough estimate of tissue density (echogenicity), shows vascular flow and velocity (color-flow Doppler), can identify regional lymphadenopathy, and aids in the accurate placing of needles for diagnostic or therapeutic purposes. In addition, it is widely available, relatively rapid and cheap, visualizes the whole anterior neck, and does not involve ionizing irradiation. This article aims at clarifying the role of US in clinical thyroidology by pointing to areas where the technology can aid in clinical decision making. It is argued that more clinician endocrinologists should master and use this technology for diagnostic and therapeutic purposes.

[Chronic autoimmune thyroiditis in the child]

OBJECTIVE

The aim of the study was to describe the clinical characteristics and long-term follow-up of a group of children with chronic autoimmune thyroiditis.

PATIENTS AND METHODS

Sixty children (age: 11.9 +/- 2.7 years) were studied in a retrospective analysis.

RESULTS

At diagnosis, 34 of the children were hypothyroid (compensated hypothyroidism, n = 15; true hypothyroidism, n = 19) and 26 euthyroid. Thyroid ultrasonography showed characteristic features of heterogenicity and/or hypoechogenicity in all patients. Other autoimmune diseases were found in ten subjects (17%) and 23% had a family history of thyroid disease. At the end of the follow-up, nine of 45 children (20% of the cases) followed up for at least one year (mean follow-up 4.4 +/- 3.7 years), demonstrated a change in thyroid function. Hypothyroidism was detected in two initially euthyroid patients. Among initially hypothyroid patients, seven (28%) recovered normal thyroid function, allowing L-thyroxine withdrawal for four weeks, after 1.5 to 8.4 years. No factor was found to be predictive of the course of the disease. All subjects treated with L-thyroxine for hypothyroidism reached normal final height.

CONCLUSION

The natural course of chronic lymphocytic thyroiditis is variable and unpredictable. Recovery from hypothyroidism does occur and can be aided by the L-thyroxine withdrawal test. The disease requires lifelong thyroid surveillance, especially in women during pregnancy, in order to avoid a potential adverse effect on the future child.

Differences in the levels of TSH-binding inhibitor immunoglobulins in goitrous and agoitrous autoimmune thyroiditis after twelve months of L-thyroxine therapy

OBJECTIVE

The aims were to study the prevalence of TSH binding inhibitor immunoglobulins (TBII) in newly diagnosed patients with autoimmune hypo-thyroidism, to determine if clinical and biochemical parameters in these patients differed, and to study the course of these antibodies after 12 months of L-thyroxine (LT4) therapy.

SUBJECTS AND DESIGN

In a prospective study, 111 consecutive patients with newly diagnosed auto-immune hypothyroidism were enrolled. Patients were divided into groups according to the presence or absence of a goitre and TBII levels. Clinical and biochemical differences in these patients were analysed. Patients were then treated with L-thyroxine (LT4) for 12 months and changes in their TBII monitored.

MEASUREMENTS

Free T4 and TSH levels were measured at baseline and then 6-weekly during the titration of LT4 doses. Once TSH levels had normalized, these measurements were performed 3 monthly. TBII levels were measured in patients at baseline and 12 months. Thyroid stimulating blocking antibody (TSBAb) levels were measured 12-18 months after initiation of LT4 therapy.

RESULTS

Twenty patients were TBII-positive, 10 goitrous and 10 agoitrous. Agoitrous TBII-positive patients were found to have similar characteristics: these included TBII levels > 100 U/l, potent thyroid stimulating blocking antibody (TSBAb) activity and a tendency for TBII levels to remain unchanged or to rise after LT4 therapy. The degree of hypothyroidism seen in these cases was significantly greater than in all other groups. In contrast, goitrous TBII-positive patients were heterogenous, most did not have significant TSBAb activity and TBII disappeared in 5 out of 10 cases after a year of LT4 treatment. While TBII disappeared in 6 of the 20 patients after a year, remission of hypothyroidism occurred in only 3 cases.

CONCLUSIONS

The degree of hypothyroidism in agoitrous TSH-binding inhibitor immunoglobulins-positive patients appears to be more severe than that seen in other forms of AIT. The differences in thyroid stimulating blocking antiboby activity and response to LT4 therapy in agoitrous and goitrous autoimmune thyroiditis suggest that the TSH-binding inhibitor immunoglobulins in these patients are fundamentally different. The disappearance of TSH-binding inhibitor immunoglobulins in hypothyroid patients was not accompanied by the reversal of hypothyroidism in 50% of patients.

High prevalence and little change in TSH receptor blocking antibody titres with thyroxine and antithyroid drug therapy in patients with non-goitrous autoimmune thyroiditis

OBJECTIVE

We have reevaluated the prevalence and pathogenetic importance of TSH receptor blocking antibodies (TRBAb) in autoimmune hypothyroidism, and investigated the changes in TRBAb activities during thyroxine and antithyroid drug treatment.

DESIGN

Serum TSH binding inhibitor immunoglobulin (TBII) and thyroid stimulation blocking antibody (TSBAb) were measured serially in all patients with non-goitrous autoimmune thyroiditis (AT) and measured monthly during methimazole treatment in 6 patients.

PATIENTS

Ninety patients with non-goitrous AT and 95 patients with goitrous AT were entered consecutively into this study. All patients with non-goitrous AT were treated with thyroxine and followed at intervals of 6 months for 2 years initially and then yearly intervals. The duration of follow-up was 1-8 years. Six patients from the TRBAb-positive non-goitrous AT group who were treated with thyroxine were randomly selected and given additional treatments with methimazole (40 mg per day) for 6 months.

MEASUREMENTS

Serum TBII was measured by a radioreceptor assay, TSBAb by using FRTL-5 cells, and antithyroid peroxidase and antithyroglobulin antibodies by radioimmunoassay.

RESULTS

The prevalences of TBII and TSBAb is non-goitrous AT were 47.8 and 58.9%, respectively, which were significantly higher than those in goitrous AT (6.3% for TBII, 10.5% for TSBAb). All but one patient showed persistent TBII and TSBAb activities during the thyroxine treatment for up to 8 years. A high dose of methimazole (40 mg per day) did not affect the titres of TBII and TSBAb in 5 out of 6 patients with non-goitrous AT tested. However, antithyroid peroxidase and antithyroglobulin antibodies activities were significantly decreased during the methimazole treatment.

CONCLUSION

The high prevalence of TSH receptor blocking antibodies (TRBAb) suggests that TRBAb may play a major role in the development of hypothyroidism and thyroid atrophy in the vast majority of patients with non-goitrous autoimmune thyroiditis. Most TRBAb activities are stable for at least 8 years and are now affected by thyroxine and antithyroid drug treatment.

Isohormonal therapy of endocrine autoimmunity

For most autoimmune disorders, the site (if any) of chronic immunization required for perpetuation of autoimmunity is unknown. However, one possible site is the target organ itself. If this were the case, feedback regulation of target cell activity might influence autoimmunity. Here, Nanette Schloot and George Eisenbarth review several recent studies suggesting that therapies that inhibit hormonal secretion of target endocrine organs, and/or modulate immunity by therapy with the isohormone, are associated with disease suppression.

Frequency of Hashimoto's thyroiditis in children with type 1 diabetes mellitus

A total of 1419 children with type 1 diabetes mellitus was investigated in order to assess the true frequency of Hashimoto's thyroiditis (HT), diagnosed by microsomal and/or thyroglobulin autoantibodies, by ultrasound and in many cases also by fine needle biopsy. According to these criteria, 55 cases (3.9%) of HT were identified, a number significantly higher (P < 0.0001) than the distribution reported in the normal paediatric population. No typical antibody pattern was seen prior to the onset of HT, nor was an antibody threshold level found which could have been diagnostic for this disease. Patients with subclinical hypothyroidism were treated with L-thyroxine and were investigated regarding the behaviour of anti-thyroid autoantibodies; however, no significant changes were seen. The data showed a high frequency of HT in diabetic children, and therefore we recommend that children with type 1 diabetes mellitus should be screened for thyroid autoantibodies and those positive should undergo periodic thyroid function testing.

Two cases of therapeutic failure associated with levothyroxine brand interchange

OBJECTIVE

To report the loss of therapeutic control in 2 hypothyroid patients and remind clinical pharmacists and other healthcare professionals to remain cognizant of possible product quality differences within or bioequivalency differences between levothyroxine products.

CASE SUMMARIES

Two patients with stable hypothyroidism experienced symptoms of hypothyroidism with increased serum thyroid-stimulating hormone (TSH) concentrations after switching from 1 levothyroxine product to another. One tablet from 1 of the patient's levothyroxine prescriptions was assayed, and its levothyroxine content was 74.5% of the label claim, a value outside of the United States Pharmacopeia requirements of 90-110%.

DISCUSSION

Two patients with hypothyroidism had remained euthyroid and stable while receiving 1 levothyroxine product, but became symptomatic with dramatically increased serum TSH concentrations while receiving what were thought to be comparable dosages of another levothyroxine product. Therapeutic control was reestablished in both patients after therapy with the original levothyroxine product was reinstated.

CONCLUSIONS

Clinical pharmacists and other healthcare professionals should remain cognizant of possible product quality differences within or bioequivalency differences between levothyroxine products. These differences necessitate close monitoring of hypothyroid patients, counseling these patients about the clinical signs of sub- and supratherapeutic levothyroxine dosages, and prudence when switching patients with stable hypothyroidism to alternative levothyroxine products. If there are inconsistencies between levothyroxine products, resultant deleterious effects on the therapeutic stability of patients with hypothyroidism may undermine cost savings that might be incurred by such a change. If these patients are switched to alternative levothyroxine products, it is recommended that thyroid function tests be repeated after equilibration to the new product.

Effects of thyroid status on thyroid autoimmunity expression in euthyroid and hypothyroid patients with Hashimoto's thyroiditis

OBJECTIVE

In patients with hypothyroid goitrous Hashimoto's thyroiditis, the recovery from hypothyroidism seems to be due to a spontaneous decrease of antibodies (Ab) to the TSH-receptor (R). In contrast, in patients with Graves' disease made euthyroid by antithyroid drug therapy, the suppression of TSH secretion by thyroid hormone during antithyroid drug treatment decreases the production of Ab to TSH-R. We investigated in patients with initially euthyroid or hypothyroid goitrous Hashimoto's thyroiditis the relationships between thyroid status and the serum TSH-R, peroxidase (TPO) and thyroglobulin (Tg) Ab concentrations in untreated or L-thyroxine (T4) treated patients.

PATIENTS

A prospective study of 174 consecutive patients, referred with goitrous Hashimoto's disease in an initially euthyroid (group I, n = 78) or hypothyroid (group II, n = 96) state. The patients with positive (> or = 7%) TSH-RAb (group I, n = 18; group II, n = 22) were reinvestigated 12 months after the initiation of L-T4 therapy. After which, (1) L-T4 was continued and an evaluation performed 2 months later (i.e. 14 months after L-T4 initiation) in 9 patients of group I and in 11 patients of group II or (2) L-T4 was withdrawn and an evaluation performed 2 months later in 9 patients of group I and in 11 patients of group II.

MEASUREMENTS

Measurements of basal plasma TSH, free T4 (FT4) and total T3 and serum TSH-R, TPO and TgAb.

RESULTS

The prevalence of positive TSH-RAb levels did not differ between group I (23.1%) and group II (22.9%). However, the mean TSH-RAb level in group I (9.4 +/- 0.4%) was lower (P < 0.01) than in group II (11.6 +/- 0.5%). In the patients with positive TSH-R Ab, (1) the prevalences of positive TSH-RAb decreased (P < 0.001) under L-T4 therapy (group I = 22.2%, group II = 21.2%) and increased again (P < 0.01) 2 months after L-T4 cessation (group I = 77.7%, group II = 63.6%) to reach lower levels (group I, P < 0.05; group II, P < 0.01) than those obtained prior to L-T4 treatment. Statistical analysis of TSH levels through the course of the study confirmed these results. (2) In contrast to the variations of the mean TgAb values, the variations of the mean TPOAb levels in each group were in good agreement with those of TSH-RAb through the course of the study. (3) There were significant correlations between some parameters of thyroid status and both TSH-RAb (TSH, r = 0.43, P < 0.001; FT4, r = -0.35, P < 0.01) and TPOAb (TSH, r = 0.42, P < 0.001; FT4, r = -0.31; P < 0.01) levels. In contrast, no correlations were found between thyroid status and TgAb values.

CONCLUSIONS

This study demonstrates that thyroid status can modulate thyroid autoimmunity expression, such as TSH-RAb and TPOAb, in patients with euthyroid or hypothyroid goitrous Hashimoto's thyroiditis. Similar results have been reported in patients with Graves' disease made euthyroid by the administration of thyroid hormone during antithyroid drug treatment.

Disappearance of thyrotropin-blocking antibodies and spontaneous recovery from hypothyroidism in autoimmune thyroiditis

BACKGROUND

Hypothyroidism may result from the production of antibodies that block the actions of thyrotropin. How often these thyrotropin-blocking antibodies are a cause of hypothyroidism and whether their production may cease, causing hypothyroidism to disappear, have not been extensively studied.

METHODS

We determined the frequency with which thyrotropin-blocking antibodies were present in 172 hypothyroid patients with goitrous autoimmune thyroiditis (Hashimoto's disease) and 64 hypothyroid patients with atrophic autoimmune thyroiditis (idiopathic primary hypothyroidism). For 6 to 11 years we then followed 21 of these patients who were found to have thyrotropin-blocking antibodies. They received levothyroxine therapy for 3.5 to 8 years, after which it was discontinued. At frequent intervals during this time we measured the patients' serum concentrations of thyroxine, triiodothyronine, thyrotropin, and thyrotropin-blocking antibodies (measured as immunoglobulins that inhibit thyrotropin binding and immunoglobulins that inhibit thyrotropin bioactivity).

RESULTS

Thyrotropin-blocking antibodies were detected in 9 percent of the patients with goitrous autoimmune thyroiditis and in 25 percent of those with atrophic autoimmune thyroiditis. Among the 21 patients studied serially while receiving levothyroxine, thyrotropin-blocking antibodies disappeared in 15 (group 1), 7 of whom had goiter initially, and persisted in 6 (group 2), none of whom had goiter initially. Levothyroxine therapy was subsequently discontinued in these 21 patients. Six of those in group 1 (four with goiter) remained euthyroid (mean follow-up after discontinuation of therapy, 2.1 years), and nine became hypothyroid again within 3 months. All six patients in group 2 remained hypothyroid.

CONCLUSIONS

Hypothyroidism in some patients with autoimmune thyroiditis may be due to thyrotropin-blocking antibodies. The production of thyrotropin-blocking antibodies may subside, producing remissions of hypothyroidism. Chronic autoimmune thyroiditis may therefore cause transient as well as permanent hypothyroidism.

Influence of thyroxine treatment on thyroid size and anti-thyroid peroxidase antibodies in Hashimoto's thyroiditis

OBJECTIVE

It has been postulated that a decrease in thyroid size can be achieved by thyroxine treatment in patients with goitrous Hashimoto's thyroiditis but no objective data are available. We have therefore investigated the influence of thyroxine treatment on ultrasonically determined thyroid size. We also measured serum antithyroid peroxidase antibodies.

DESIGN

Consecutive patients with goitrous Hashimoto's thyroiditis was studied.

PATIENTS

Thirteen women participated; all had goitrous thyroiditis.

TREATMENT

To render them euthyroid thyroxine was given for 24 months.

MEASUREMENTS

Thyroid size was measured ultrasonically and antithyroid peroxidase antibodies were measured using a commercial radioimmunological method.

RESULT

Concomitant with the gradual increase in serum free thyroxine and free triiodothyronine index values and a fall in serum thyrotrophin level, a gradual decrease in thyroid volume from 50.4 +/- 6.8 ml (mean +/- SEM) to 34.1 +/- 5.7 ml (32%), P less than 0.001 was demonstrated. Antithyroid peroxidase antibodies were present in high concentrations in all subjects but the mean serum level was not significantly changed at 24 months after initiation of treatment.

CONCLUSION

A clinically significant reduction in thyroid volume related to normalization of thyroid function but unrelated to changes in antithyroid peroxidase antibody can be achieved during L-thyroxine treatment of hypothyroid goitrous Hashimoto's thyroiditis.