Hyperthyroidism

In-silico studies of Brassica oleracea active compounds and their role in thyroid peroxidase activity

Cabbage, a leafy vegetable that is widely consumed across the globe, holds a significant place within the Brassica family. For almost a century, its potential anti-thyroid effects have captured attention. The presence of compounds such as thiocyanate and goitrin in cabbage has been extensively investigated for their ability to impede sodium-iodide symporter and thyroid peroxidase (TPO) activities. The present study is focused on uncovering the active constituents in cabbage that could interact with TPO, while also examining their stability under cooking temperatures. Employing molecular docking and molecular dynamic simulation techniques, we quantified the binding strength of phytochemicals present in cabbage with the target. Out of the 60 compounds identified in cabbage leaves, only 18 exhibited docking scores surpassing those of the commercially available anti-thyroid drug, methimazole. These chosen compounds were studied for binding free energy and pharmacokinetic properties. A specific compound, gamma-Terpinene, classified as a monoterpene, emerged as noteworthy due to its alignment with all criteria and the highest observed binding free energy compared to others. Furthermore, we explored the stability of gamma-Terpinene at 373.15K (cooking temperature) and observed its susceptibility to degradation. This might contribute to the relatively diminished anti-thyroid effects of cabbage when consumed in cooked form. Consequently, our findings suggest that the consumption of cooked cabbage could be more conducive to maintaining normal thyroid function, as opposed to its raw counterpart.Communicated by Ramaswamy H. Sarma.

Effects of Methimazole vs Propylthiouracil in Newborns: A Comparative Review

Hyperthyroidism is more common in women and the sensitivity of thyroid function changes during pregnancy. Excess levels of thyroid hormones and thioamides have a major impact on maternal and fetal outcomes. Our aim was to perform an extensive literature review and provide relevant details concerning the analytical and clinical aspects of the potential effects of the two main drugs used (methimazole and propylthiouracil) in newborns. A thorough literature review was conducted using PubMed and Google Scholar databases. In total, 10 relevant studies were identified and data from these studies were extracted and then extrapolated into results after analysis. Three out of four studies that used methimazole and carbimazole, one and two, respectively, showed adverse fetal outcomes requiring surgical management for congenital anomalies like aplasia cutis, patent vitellointestinal duct, and gastroschisis. Out of the three studies that used propylthiouracil, one baby underwent surgery for bilateral pyelectasis, vesicovaginal fistula, anal stenosis, and polydactyly. The findings of the aforementioned studies provide enough evidence to imply that the use of methimazole and carbimazole to treat antenatal hyperthyroidism has worse fetal outcomes than the use of propylthiouracil. Also, given the paucity of data in the existing literature regarding propylthiouracil's effects on newborns, further studies in this demographic are needed.

Low Thyroid-stimulating Hormone Levels Are Associated With Annoying Tinnitus in Adult Women: Korea National Health and Nutrition Examination Surveys

OBJECTIVE

This study aimed to investigate the relationship between thyroid function and tinnitus.

STUDY DESIGN

A cross-sectional study.

SETTING

The Korean National Health and Nutrition Examination Survey from 2013 was used.

PATIENTS AND INTERVENTIONS

A total of 1,165 participants ≥ 40 years old who were surveyed for the presence of tinnitus and underwent thyroid function tests were included. The presence of discomfort from tinnitus was defined as annoying tinnitus. The control group included participants with "no tinnitus" or "no discomfort from tinnitus." The participants were divided into the annoying tinnitus group and the control group.

MAIN OUTCOME MEASURES

The associations of free thyroxine and thyroid-stimulating hormone (TSH) with annoying tinnitus were analyzed using logistic regression with complex sampling methods. Subgroup analyses were performed according to sex.

RESULTS

The low TSH level group had 2.35-fold greater odds of annoying tinnitus than the control group (95% confidence interval  = 1.10-5.12, p = 0.027). Even in patients with a normal free thyroxine level, a low TSH level was related to 2.78-fold higher odds of annoying tinnitus (95% confidence interval  = 1.21-6.38, p = 0.016). In subgroup analyses, this association was apparent in the female subgroup. The male subgroup did not show a relationship between low TSH levels and annoying tinnitus.

CONCLUSIONS

Subclinical hyperthyroidism was related to an increased risk of annoying tinnitus. This relationship was apparent in the female subgroup.

Current approach to surgical management of hyperthyroidism

Hyperthyroidism is a set of disorders that involve excess synthesis and secretion of thyroid hormones by the thyroid gland, which leads to thyrotoxicosis. The most common forms of hyperthyroidism include diffuse toxic goiter (Graves' disease), toxic multinodular goiter (Plummer disease), and a solitary toxic adenoma. The most reliable screening measure of thyroid function is the thyroid-stimulating hormone (TSH) level. Options for treatment of hyperthyroidism include: antithyroid drugs, radioactive iodine therapy (the preferred treatment of hyperthyroidism among US thyroid specialists), or thyroidectomy. Massive thyroid enlargement with compressive symptoms, a suspicious nodule, Graves' orbitopathy, and patient preference are indications for surgical treatment of thyrotoxicosis. This paper reviews the current literature and controversies on the surgical approach to the management of hyperthyroidism.

Hyperthyroidism and hepatic dysfunction: Report of 17 cases

Aims

Hyperthyroidism has been known to be associated with abnormalities of serum liver chemistry. The objective of our study is to describe clinical, biochemical and therapeutic features of hepatic dysfunction in hyperthyroidism.

Methods and Results

This retrospective study was conducted on patients hospitalized in our endocrinology department over 20 years. We included patients with untreated and noniatrogenic hyperthyroidism among whom biochemical findings noted hepatic dysfunction and excluded those with concomitant liver disease. Our population is composed of 10 men and 7 women. The average age was 41.4 years. The mean serum level of free thyroxine was 83.8 pmol/L. The serum thyrotropin level was below the detection limit in 10/17 cases. Graves' disease was the most frequently found etiology of hyperthyroidism. Fourteen patients had hyperthyroidism's complications. Eleven patients manifested congestive heart failure. Hepatic dysfunction was moderate and severe in eight and two cases, respectively. Fifteen patients had cholestasis, associated with jaundice in five cases. Hepatocellular injury and synthetic liver dysfunction were noted in seven and five cases, respectively. Thyroid peroxidase antibodies were positively correlated with the serum level of bilirubin (ρ = 0.695; P = 0.038). A negative correlation was noted between alanine aminotransferase and left ventricular ejection fraction (ρ = −0.812; P = 0.05). Radioactive iodine was indicated in 15/17 cases. Follow‐up liver tests were performed in 11 cases. They all had normalized hepatic function once euthyroidism restored.

Conclusion

Liver injury in hyperthyroidism is relatively common, ranging from mild to severe. Therefore, patients presenting unexplained hepatic abnormalities require close examination and an evaluation of the thyroid function should be sought.

Evaluation of ultrasonographical and cytological features of thyroid nodules in patients treated with radioactive iodine for hyperthyroidism

BACKGROUND

In this study, we aimed to evaluate ultrasonographical and cytological features of thyroid nodules in patients who were treated with radioactive iodine (RAI) for hyperthyroidism years ago.

METHODS

Patients who had a history of RAI treatment for hyperthyroidism and had thyroid nodules that were evaluated with fine-needle aspiration biopsy (FNAB) were included in the study.

RESULTS

There were 27 patients (22 female and 5 male) with a mean age of 59.3 ± 13.5. The indication for RAI treatment was Graves in 5 (18.6%), toxic nodular or multinodular goiter in 16 (69.2%), and unknown in 6 (22.2%) patients. A total of 48 thyroid nodules were evaluated with FNAB and cytological diagnosis were benign in 24 (50.0%), nondiagnostic in 15 (31.2%), atypia of undetermined significance in 5 (10.4%), suspicous for malignancy in 2 (4.2%), and malignant in 2 (4.2%) nodules. Thyroidectomy was performed in 10 patients, 5 were benign (50.0%), and 5 (50.0%) were malignant histopathologically. Ultrasonography features of 31 cytologically/histopathologically benign and five cytologically/histopathologically malignant nodules were compared. Prevalence of isoechoic nodules was higher in benign nodules (P = .025). Macrocalcification was observed in 4 (80.0%) of malignant and 10 (32.3%) of benign nodules (P = .042).

CONCLUSION

In patients with a history of RAI treatment for hyperthyroidism, thyroid nodules with suspicious ultrasonography features, particulary hypoechoic appearence and macrocalcification, should be evaluated with FNAB irrespective of the time elapsed after RAI treatment.

Design, Synthesis, Molecular Modeling, and Biological Evaluation of Novel Thiouracil Derivatives as Potential Antithyroid Agents

Hyperthyroidism is the result of uncontrolled overproduction of the thyroid hormones. One of the mostly used antithyroid agents is 6-n-propyl-2-thiouracil (PTU). The previously solved X-ray crystal structure of the PTU bound to mammalian lactoperoxidase (LPO) reveals that the LPO-PTU binding site is basically a hydrophobic channel. There are two hydrophobic side chains directed towards the oxygen atom in the C-4 position of the thiouracil ring. In the current study, the structural activity relationship (SAR) was performed on the thiouracil nucleus of PTU to target these hydrophobic side chains and gain more favorable interactions and, in return, more antithyroid activity. Most of the designed compounds show superiority over PTU in reducing the mean serum T4 levels of hyperthyroid rats by 3% to 60%. In addition, the effect of these compounds on the levels of serum T3 was found to be comparable to the effect of PTU treatment. The designed compounds in this study showed a promising activity profile in reducing levels of thyroid hormones and follow up experiments will be needed to confirm the use of the designed compounds as new potential antithyroid agents.

Enteric Microbiota⁻Gut⁻Brain Axis from the Perspective of Nuclear Receptors

Nuclear receptors (NRs) play a key role in regulating virtually all body functions, thus maintaining a healthy operating body with all its complex systems. Recently, gut microbiota emerged as major factor contributing to the health of the whole organism. Enteric bacteria have multiple ways to influence their host and several of them involve communication with the brain. Mounting evidence of cooperation between gut flora and NRs is already available. However, the full potential of the microbiota interconnection with NRs remains to be uncovered. Herewith, we present the current state of knowledge on the multifaceted roles of NRs in the enteric microbiota–gut–brain axis.

Effectiveness of Radioiodine Treatment for Toxic Nodular Goiter

OBJECTIVE

The aim of this retrospective study is to evaluate the treatment outcomes in patients with toxic nodular goiter (TNG) that received radioiodine treatment (RAIT) and to determine the influence of age, gender, nodule size, I-131 dose, underlying etiology and antithyroid drugs on the outcomes of RAIT.

METHODS

Two hundred thirty three patients (mean 64±10 years old) with TNG that received RAIT were included in the study. Treatment success was analyzed according to demographic (age and gender) and clinical data (thyroid function tests before and after RAIT, thyroid sonography and scintigraphy, I-131 dose, antithyroid drugs). A fixed dose of 555 MBq was administered to patients with nodules smaller than 2 cm in diameter and of 740 MBq to patients with nodules larger than 2 cm. Hyperthyroidism treatment success was defined as achieving hypothyroidism or euthyroidism six months after RAIT.

RESULTS

In our study, the cure rate was 93.9% six months after RAIT. Hypothyroidism was observed in 74 (31.7%) patients, and euthyroidism was achieved in 145 (62.2%) patients while 14 (6%) patients remained in hyperthyroid state. Age and gender did not affect treatment outcomes. No correlation was found between underlying etiology or antithyroid drugs and therapeutic effectiveness. The effectiveness of RAIT was better in patients with nodules smaller than 2 cm.

CONCLUSION

We observed that high cure rates were obtained in patients with TNG with 555 MBq and 740 MBq doses of I-131. While nodule diameter and RAI dose are important factors for treatment efficacy; age, gender, underlying etiology and antithyroid drugs do not affect the outcome of RAIT.

Increased risk of hypothyroidism and hyperthyroidism in patients with major depressive disorder: a population-based study

OBJECTIVE

To determine the prevalence and incidence of hypothyroidism, hyperthyroidism, and risk factors in patients with major depressive disorder (MDD).

METHODS

The National Health Research Institute provided a database of 1,000,000 random subjects for health service studies. We identified subjects aged ≥18 years who had at least 1 service claim during 2005 with a primary diagnosis of MDD or with a primary or secondary diagnosis of hypothyroidism or hyperthyroidism. We also compared the incidence of hypothyroidism and hyperthyroidism among patients with MDD and the general population from 2006 through 2010.

RESULTS

The prevalence of hypothyroidism in patients with MDD was higher than that in the general population (1.20% vs. 0.30%; odds ratio, 3.08; 95% confidence interval, 2.35-4.03) in 2005. The prevalence of hyperthyroidism was also higher in patients with MDD than in the general population (2.46% vs. 0.79%; odds ratio, 2.77; 95% confidence interval, 2.29-3.35) in 2005. The annual incidence of hypothyroidism was higher in patients with MDD than that in the general population (0.40% vs. 0.13%; risk ratio, 2.47; 95% confidence interval, 2.00-3.06). The annual incidence of hyperthyroidism was also higher in patients with MDD than that in the general population (0.72% vs. 0.32%; risk ratio, 2.06; 95% confidence interval, 1.75-2.43).

CONCLUSIONS

Patients with MDD had a higher prevalence and a higher incidence of hypothyroidism or hyperthyroidism than the general population. Female sex was a risk factor for hypothyroidism and hyperthyroidism in MDD.

Effect of stressful life events on the initiation of graves' disease

OBJECTIVE

The aim of this study was to investigate the relationship between stressful life events (LESs) and its effect on the initiation of Graves' disease (GD) and toxic nodular goitre (TNG).

PATIENTS AND METHOD

Forty-five patients with GD, 24 patients with TNG and 36 healthy control (CG) were included to the study. Graves and TNG patients had diagnosed within the last 12 months, with clinical and biochemical confirmation in Endocrinology Metabolism Outpatient Clinic of Cerrahpasa Medical School. The Holmes-Rahe Stress Scale and the Life Experience Survey (LES) was the psychological evaluation instrument used in this study.

RESULTS

There was no significant difference according to Holmes-Rahe scale (Graves & TNG P = 0.329, Graves & Control P = 0.115, TNG and control P = 0.571). According to LES scale when negative event number, positive event number, neutral events and their effects are considered, between Graves and TNG groups no statistically difference was observed (P = 0.139, P = 0.083, P = 0.167, P = 0.162, P = 0.861). The number and impact of negative SLEs were significantly higher in GD compared to CG (P = 0.015, P < 0.001).

CONCLUSION

According to LES scale GD patients has significant difference with respect to CG when negative event number and impact are considered.

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.

The impact of carvedilol and metoprolol on serum lipid concentrations and symptoms in patients with hyperthyroidism

BACKGROUND

Hyperthyroidism is associated with unpleasant symptoms and hypertension due to increased adrenergic tone. Therefore, beta-blockers are often used in hyperthyroid patients. While some beta-blockers (such as propronolol and metoprolol) may have unwanted effects on lipid profile, carvedilol, a new alpha- and beta-blocker, has been suggested to have some metabolic advantages with respect to lipid profiles in hypertensive patients. However, this has not been shown in hyperthyroid patients.

OBJECTIVE

We aimed to compare the effects of two beta-blockers (metoprolol and carvedilol) on the lipid profiles of hyperthyroid patients with hypertension.

METHODS

Thirty patients with hyperthyroidism and hypertension were randomly assigned to receive either carvedilol (n = 15) or metoprolol (n = 15). Thyroid-stimulating hormone (TSH), free T3, free T4, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglyceride, and total cholesterol levels were measured before and following 3 months of treatment.

RESULTS

Systolic and diastolic blood pressure, heart rate, TSH, and free T4 improved significantly in both treatment groups. There were no statistically significant changes in the lipid parameters in either of the two treatment groups; however, triglyceride levels slightly decreased with carvedilol treatment. There were also no differences between the two groups in terms of the typical symptoms of hyperthyroidism.

CONCLUSION

Carvedilol might be a preferred agent to treat hyperthyroid patients who have hypertension and dyslipidemia. This is likely due to the possible beneficial effect of carvedilol on lipid parameters, especially on triglyceride levels.

Essential tremor

Essential tremor (ET) is among the most common neurological disorders. This chapter reviews the epidemiology, clinical features, and pathophysiology of ET. The defining feature is a kinetic tremor of the arms. Patients often have a postural tremor as well. Other body regions may also be involved (especially the head). The severity of tremor may range from mild cases in population settings to more severe cases in treatment settings. Motor features aside from tremor have been described in ET, including tandem gait difficulty. Mild cognitive changes (especially executive dysfunction) have been documented in many studies as well. Despite being regarded as one of the most common hyperkinetic movement disorders, establishing a precise prevalence has been difficult, yet the prevalence among persons aged 40 and older seems to be 4% or higher. There are numerous examples of families in which the disease appears to be inherited yet genetic studies have not progressed to the point where ET genes have been identified. There is also a growing understanding that environmental factors are likely to contribute to the etiology of ET. More recent postmortem studies have helped localize the possible source of ET to structural alterations in the cerebellum and its connecting pathways.

Screening for thyroid disease: defining high-risk populations

The pros and cons of population screening for thyroid disease have been hotly debated over the past several decades. This article addresses the issue from the point of view of the potential benefit of screening, that is, disease detection. Earlier diagnoses of hypothyroidism, hyperthyroidism, thyroid nodules, thyroid cancer and so on, with implementation of the indicated diagnostic and therapeutic interventions, avoid the adverse consequences of unrecognized and untreated progressive disease. Arguments against screening and case-finding often focus on cost considerations. To achieve the greatest yield at the lowest cost, our emphasis is on vulnerable populations with associated risk factors, and special situations such as pregnancy.

Liver X receptor beta and thyroid hormone receptor alpha in brain cortical layering

In the past year, two members of the nuclear receptor family, liver X receptor beta (LXRbeta) and thyroid hormone receptor alpha (TRalpha), have been found to be essential for correct migration of neurons in the developing cortex in mouse embryos. TRalpha and LXRbeta bind to identical response elements on DNA and sometimes regulate the same genes. The reason for the migration defect in the LXRbeta(-/-) mouse and the possibility that TRalpha may be involved are the subjects of the present study. At E15.5, expression of reelin and VLDLR was similar but expression of apolipoprotein E receptor 2 (ApoER2) (the reelin receptor) was much lower in LXRbeta(-/-) than in WT mice. Knockout of ApoER2 is known to lead to abnormal cortical lamination. Surprisingly, by postnatal day 14 (P14), no morphological abnormalities were detectable in the cortex of LXRbeta(-/-) mice and ApoER2 expression was much stronger than in WT controls. Thus, a postnatal mechanism leads to increase in ApoER2 expression by P14. TRalpha also regulates ApoER2. In both WT and LXRbeta(-/-) mice, expression of TRalpha was high at postnatal day 2. By P14 it was reduced to low levels in WT mice but was still abundantly expressed in the cortex of LXRbeta(-/-) mice. Based on the present data we hypothesize that reduction in the level of ApoER2 is the reason for the retarded migration of later-born neurons in LXRbeta(-/-) mice but that as thyroid hormone (TH) increases after birth the neurons do find their correct place in the cortex.

Severe hyperthyroidism: aetiology, clinical features and treatment outcome

BACKGROUND

Severe hyperthyroidism (SH) is a serious medical disorder that can compromise life. There have not been systematic studies in which SH has been evaluated in detail. Here, our aims were: (1) to analyse both clinical and analytical features and outcome in patients with SH and (2) to compare these data with those found in more usual forms of hyperthyroidism. Patients and methods All patients diagnosed of SH (free thyroxine, FT4 > 100 pmol/l, NR: 11-23) seen in our endocrinology clinic in the last 15 years were studied and compared with a sample of patients with mild (mH; FT4, 23-50 pmol/l) and moderate (MH; FT4, 51-100 pmol/l) hyperthyroidism. Aetiology, clinical analytical and imaging data at diagnosis, therapeutic response and outcome were registered. Results A total of 107 patients with overt hyperthyroidism (81 females, mean age +/- SD 46.9 +/- 16.1 years) were evaluated. We studied a historic group with SH (n = 21; 14 females, 40.9 +/- 17.2 years) and, as a comparator group, we analyszed the data of 86 hyperthyroid patients (67 females, 48.4 +/- 15.5.6 years, NS) comparable in age and gender. The comparator group was classified in MH (n = 37, 26 females, 47.2 +/- 16.6 years) and mH (n = 49, 41 females, 49.4 +/- 14.8 years). In comparison with mH group, SH patients were significantly (P < 0.05) younger and showed a greater proportion of first episode of thyroid hyperfunction (P < 0.05). Graves' disease was the main aetiology in the three groups, but patients with SH showed the highest titre of TSH-receptor antibodies (TRAb) (P < 0.001). Heart rate and size of goitre were higher in SH group than in mH and MH groups (P < 0.01). Atrial fibrillation was more frequently reported in SH group than in MH and mH groups (15.8%vs. 5.4% and 0%, respectively, P < 0.05).

RESULTS

from logistic regression analysis showed that younger age [OR 0.958 (95% CI, 0.923-0.995), P = 0.026], presence of asthenia [OR 4.35 (1.48-12.78), P = 0.008] and higher heart rate [OR 1.03 (1.01-1.06), P = 0.013] were independent clinical variables associated to SH. SH patients showed similar biochemical parameters in comparison with mH group, except for increased serum aspartate aminotransferase (AST) (P < 0.01) and calcium (P < 0.05) levels, and decreased serum cholesterol (P < 0.05) and albumin (P < 0.05) concentrations. Logistic regression analysis showed that only AST [OR 1.07 (1.02-1.11), P = 0.005] was an independent biochemical variable associated to SH. No differences in the type of therapy, cure rate and time in achieving cure were found in SH subjects in relation to patients with milder forms of hyperthyroidism. FT4 was the only independent predictor of cure [OR 0.98 (CI 95%, 0.97-0.99), P < 0.05].

CONCLUSIONS

Graves' disease is the most common aetiology in patients with SH. This type of hyperthyroidism is usually de novo and is accompanied by more clinical signs, symptoms, and analytical derangements, as well as higher titres of TRAb at diagnosis than milder forms of hyperthyroidism. The present data are not able to show differences in treatment modality, time to achieve cure, and remission rate among patients with mild, moderate and severe hyperthyroidism.

Current and emerging treatment options for Graves' hyperthyroidism

Radioiodine, antithyroid drugs and surgery have been well established therapies for Graves' hyperthyroidism for several decades. However there remain large variations in practice among physicians in the preferred modality and the method of administration. Patient choice and perceptions also play a big role in the choice of treatment. Radioiodine may be given using fixed high doses or by calculated doses following uptake studies. The risks of radioiodine including eye disease and the role of prophylactic steroid therapy are discussed. The commonly used antithyroid drugs include carbimazole, methimazole and propylthiouracil; however a number of other agents have been tried in special situations or in combination with these drugs. The antithyroid drugs may be given in high (using additional levothyroxine in a block-replace regimen) or low doses (in a titration regimen). This review examines the current evidence and relative benefits for these options as well as looking at emerging therapies including immunomodulatory treatments such as rituximab which have come into early clinical trials. The use of antithyroid therapies in special situations is also discussed as well as clinical practice issues which may influence the choices.

Dramatic response to cholestyramine in a patient with Graves' disease resistant to conventional therapy

BACKGROUND

Resistance to the conventional treatment of hyperthyroidism with antithyroid drugs is not commonly found in clinical practice, and only few other treatment options have been reported on in detail. For example, surgery or radioiodine ablation are well-accepted interventions that must be always considered. The euthyroid state is strongly recommended before both of these as this might reduce complications. There are few studies indicating that bile acid sequestrants, when added to antithyroid drugs, produce a more rapid decline in serum thyroid hormone levels and that this effect is maintained for at least 4 weeks. Complete normalization of serum thyroid hormone levels is generally not expected, however.

SUMMARY

We report a patient whose thyrotoxicosis failed to respond to conventional treatment. The patient remained persistently hyperthyroid, both clinically and biochemically, despite several months of methimazole and propranolol and the addition of iodine. Cholestyramine, a bile acid sequestrant, was then added, and a dramatic improvement was observed.

CONCLUSION

We report a patient who was resistant to conventional antithyroid drugs in whom thyroid hormone levels completely normalized after 1 week of additional treatment with cholestyramine.