Effects of tyrosine kinase inhibitors on thyroid function and thyroid hormone metabolism.

The increasing knowledge of the molecular mechanisms in the cell signaling pathways of malignant cells, has recently led to the discovery of several tyrosine kinases (TKs), mainly TK receptors (TKR), which play a major role in the pathogenesis of many types of cancer. These receptors, physiologically involved in cell growth and angiogenesis, may harbor mutations or be overexpressed in malignant cells, and represent a target for anticancer therapy. Indeed, several therapeutic agents targeting specific altered pathways such as RET, BRAF, RAS, EGFR and VEGFR, have been identified. Tyrosine kinase inhibitors (TKIs) affect TK dependent oncogenic pathways by competing with ATP binding sites of the TK domain, thus blocking the activity of the enzyme, and thereby inhibiting the growth and spread of several cancers. Although the therapeutic action may be very effective, these molecules, due to their mechanism of multitargeted inhibition, may produce adverse events involving several biological systems. Both hypothyroidism and thyrotoxicosis have been reported during treatment with TKI, as well as an effect on the activity of enzymes involved in thyroid hormone metabolism. The pathogenic mechanisms leading to thyroid dysfunction and changes in serum thyroid function tests occurring in patients on TKI are reviewed and discussed in this manuscript.

A case of Graves' disease and type 1 diabetes mellitus following SARS-CoV-2 vaccination.

Autoimmune diseases, including autoimmune endocrine diseases (AIED), are thought to develop following environmental exposure in patients with genetic predisposition. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and vaccines against it could represent new environmental triggers for AIED. We report a patient, with history of vitiligo vulgaris and 8 years of type 2 diabetes, who came to our institution because of fever, weight loss, asthenia and thyrotoxicosis occurred 4 weeks later the administration of BNT162B2 (Pfizer-BioNTech) SARS-CoV-2 vaccine. Clinical, biochemical and instrumental work-up demonstrated Graves' disease and autoimmune diabetes mellitus. The occurrence of these disorders could be explained through different mechanism such as autoimmune/inflammatory syndrome induced by adjuvants (ASIA syndrome), mRNA "self-adjuvant" effect, molecular mimicry between human and viral proteins and immune disruption from external stimuli. However further studies are needed to better understand the underlying pathogenesis of AIED following SARS-CoV-2 vaccine.

Changes in subtypes of overt thyrotoxicosis and hypothyroidism following iodine fortification.

OBJECTIVE: To investigate the impact of mandatory iodine fortification (IF) on the incidence of nosological subtypes of overt thyrotoxicosis and hypothyroidism. DESIGN: We identified and scrutinized all possible new cases of overt thyrotoxicosis and hypothyroidism in an open cohort in Northern Jutland (n = 309 434; 1 January 1997) during the years 2014-2016. Individual medical history was evaluated to verify and detail the incidence of overt thyroid dysfunction and for classification into nosological subtypes. A number of cases were excluded during final verification due to spontaneous normalization of thyroid function, as they had no medical history suggesting a known condition, which could transiently affect thyroid function (subacute/silent thyroiditis, PPTD and iatrogenic thyroid dysfunction). An identical survey was conducted in 1997-2000 prior to mandatory IF of salt (13 µg/g) that was in effect from year 2001. RESULTS: The standardized incidence rate (SIR) of verified overt thyrotoxicosis decreased markedly from 97.5/100 000/year in 1997-2000 to 48.8 in 2014-2016 (SIRR: 0.50 [95% CI: 0.45-0.56]). This was due to a distinct decrease in the SIR of multinodular toxic goitre (SIRR: 0.18 [0.15-0.23]), solitary toxic adenoma (SIRR: 0.26 [0.16-0.43]) and to a lesser degree Graves' disease (SIRR: 0.67 [0.56-0.79]). SIR for overt hypothyroidism was unaltered by 2014-2016 (SIRR: 1.03 [0.87-1.22]). However, age distribution shifted with more young and fewer elderly cases of verified overt hypothyroidism. CONCLUSION: Mandatory IF caused a substantial reduction in SIR of verified overt thyrotoxicosis (especially of nodular origin) while avoiding an increase in SIR of verified overt hypothyroidism.

A Case of Marine-Lenhart Syndrome with Predominance of Plummer Disease.

A 74-year-old woman with a left neck mass and thyrotoxicosis was referred to our hospital, and was later diagnosed with Marine-Lenhart syndrome based on positivity for thyroid autoantibodies, ultrasonographically evident left lobe thyroid nodule with increased blood flow, and scintigraphically identified not only increased tumor-like accumulation but also diffused uptake. Disease control was difficult despite administration of antithyroid drugs, so subtotal thyroidectomy was performed. No hyperplastic changes or histopathological findings characteristic of Graves disease were evident on histopathology, so Plummer disease was considered to be dominant. In case of hot in low type which showed higher uptake in the nodule and lower uptake in the extranodular part on scintigraphy, there is a possibility of relapse in drug treatment.

Isoflavin-ß modifies muscle oxidative stress and prevents a thyrotoxicosis-induced loss of muscle mass in rats.

INTRODUCTION: We sought to verify whether isoflavin-beta (Iso-ß), a mixture of isoflavones with antioxidant properties, could prevent thyrotoxicosis-induced loss of muscle mass and the participation of oxidative stress (OS) in the mechanisms of this prevention. METHODS: Two experimental periods of thyrotoxicosis induction were used in Wistar rats: 3 and 5 days to assess Iso-ß effects before and after thyrotoxicosis-induced muscle wasting. After euthanasia, peritoneal fat and gastrocnemius muscle were collected, weighed, and muscle OS was assessed. RESULTS: Iso-ß prevented the loss of gastrocnemius mass in thyrotoxic rats through the prevention of muscle OS generation during thyrotoxicosis, increasing muscle total antioxidant capacity and decreasing mitochondrial cytochrome c oxidase activity, lipid peroxidation, and protein carbonyl content. CONCLUSION: Iso-ß decreased oxidative modification of proteins, which is known to exert a major role during proteolysis induction and is present in thyrotoxic myopathy, highlighting the potential action of Iso-ß in this complication of the disease. Muscle Nerve 56: 975-981, 2017.

RELATIONSHIP BETWEEN THE EFFECTIVENESS OF INORGANIC IODINE AND THE SEVERITY OF GRAVES THYROTOXICOSIS: A RETROSPECTIVE STUDY.

OBJECTIVE: Inorganic iodine is often used to treat patients with Graves thyrotoxicosis who do not tolerate thionamides due to adverse effects. However, predictors of continued inorganic iodine efficacy have not been fully elucidated. This study aimed to investigate the factors affecting the continued efficacy of potassium iodide (KI) in patients with Graves thyrotoxicosis. METHODS: In this study, among 1,197 patients with Graves disease who were initially treated with thionamides, we retrospectively studied 24 consecutive Japanese patients whose treatment was changed to KI alone due to the adverse effects of thionamides. We divided these patients into 2 groups: patients who had maintained euthyroid function for at least 180 days (nonrecurrence group, n = 11), and patients who had not maintained euthyroid function for 180 days (recurrence group, n = 13). RESULTS: Free triiodothyronine (FT3) and free thyroxine (FT4) levels on the day of changing from thionamides to KI were statistically higher in the recurrence group than in the nonrecurrence group (FT3, 9.3 [range, 5.2-11.6] vs. 3.7 [3.3-4.8] pg/mL, P = .02 and FT4, 3.6 [1.8-4.5] vs. 1.4 [1.2-1.9] ng/dL, P = .02). FT4 levels on the day of drug change were significantly higher in the recurrence group, even after adjusting for thionamide or KI dose. In the recurrence group, the duration of KI effect was inversed correlated with FT3 and FT4 levels on the day of drug change. CONCLUSION: Continued efficacy of KI after thionamides might be inversely correlated with thyrotoxicosis severity on the day of drug change. ABBREVIATIONS: ANOVA = analysis of variance eTV = estimated thyroid volume FT3 = free triiodothyronine FT4 = free thyroxine IQR = interquartile range KI = potassium iodide MMI = thiamazole PTU = propylthiouracil RAIT = radioactive iodine therapy TRAb = TSH receptor antibody TSH = thyroid stimulating hormone.

Ultrastructural liver changes in the experimental thyrotoxicosis.

Aim of the study is to evaluate ultrastructural changes of rat liver in experimental thyrotoxicosis. For the study, 36 male rats have been utilized, weighing approximately 150-190 g, which were divided into three groups: the first, control group (12 animals) was composed of healthy rats that received intragastric sodium chloride 0.9% solution, the second group (12 animals) - animals with experimental thyrotoxicosis, which received intragastric solution of L-thyroxine at the rate of 200 µg/kg for 2 weeks, and the third group (12 animals) - rats with experimental thyrotoxicosis, which received intragastric solution of L-thyroxine at the rate of 200 µg/kg for 4 weeks. For electron-microscopic studies small pieces of liver tissue were taken at the end of the 2nd and 4th weeks of the experiment. The material was studied and documented in electron micrographs by using a TEM-125K electron microscope. In experiment in white male rats the electron-microscopic state of the liver in thyrotoxicosis has been studied. It has been established that thyrotoxicosis is accompanied by the significant changes of the hepatocytes ultrastructure, blood and bile capillaries. Experimental thyrotoxicosis causes significant damage of the liver plasma membranes and intracellular structural components of hepatocytes and endothelial cells. In experimental thyrotoxicosis, on the background of microcirculatory disorders, significant damage of plasmatic and intracellular organoid membranes of hepatocytes in the liver develops, which has an adverse effect on the functionality of the organ. The found ultrastructural changes are aggravated depending on the duration of thyrotoxicosis.

Symptoms of thyrotoxicosis, bone metabolism and occult atrial fibrillation in older women with mild endogenous subclinical hyperthyroidism.

OBJECTIVE: The objective of this study was to evaluate symptoms of thyrotoxicosis, bone turnover, bone mineral density (BMD) and occult atrial fibrillation (AF) in women ≥65 years with mild endogenous subclinical hyperthyroidism (SCH). DESIGN: Cross-sectional and case-control study. PATIENTS: Signs and symptoms of thyrotoxicosis, serum carboxyterminal telopeptide (CTx) and procollagen type I N-terminal propeptide (PINP), BMD, resting electrocardiogram (ECG) and 72-h ECG monitoring were evaluated in 180 women ≥65 years, including 90 with mild SCH (TSH between 0·1 and 0·4 mIU/l) and 90 euthyroid controls matched for age and body mass index. RESULTS: Symptom Rating Scale scores did not differ between patients and controls. None of the patients with SCH scored 20 points, a score compatible with clinical thyrotoxicosis. Eighty patients with SCH (89%) obtained seven or fewer points, a score compatible with euthyroidism. No difference in serum CTx or PINP concentrations was observed between patients and controls. There was also no correlation between these markers and TSH, free T4 or total T3 levels. Finally, no difference in femoral neck or lumbar spine BMD was observed between patients with SCH and controls. Three patients with SCH (3·3%) and two euthyroid women (2·2%) had known AF or AF in the resting ECG. ECG monitoring for 72 h revealed episodes of occult AF in 1/87 patients with SCH and in 1/88 euthyroid women (1·1%). CONCLUSIONS: Mild endogenous SCH (TSH between 0·1 and 0·4 mIU/l) was not associated with symptoms of thyrotoxicosis, altered bone metabolism or a higher prevalence of occult AF in women ≥65 years.

[THYROID SURGERY WITH ELECTRIC WELDING OF BIOLOGICAL TISSUE: COURSE OF THE EARLY POSTOPERATIVE PERIOD].

The experience of performing surgery on the thyroid gland (TG) in 205 patients was generalised, including the use of electric welding of biological tissue technologies (EST) ­ at 95. We used the apparatus for electric welding and high frequency surgical coagulator EK300­M1 and EKVZ­300 "Patonmed" as well as the original adaptive bipolar coagulation instruments. Operations carried out under endotracheal anesthesia "open" process, completed their stratified overlay nodal joints and vacuum­suction drainage. To assess the effectiveness of EST in thyroid surgery were analyzed during the early postoperative period. The positive impact of technology EST not only on surgical tactics, but also course of the early postoperative period. Recommended use of EST as a standard for surgical interventions on the thyroid.

Protective effects of 5,7,4'-trihydroxy-6,3'dimethoxy-flavone 5-O-α-l-rhamnopyranoside, isolated from Annona squamosa leaves in thyrotoxicosis and in hepatic lipid peroxidation in rats.

Hitherto unknown protective effects of 5,7,4'-trihydroxy-6,3'dimethoxy-flavone 5-O-α-l-rhamnopyranoside (THDMF-Rha); isolated from Annona squamosa leaves were evaluated in l-thyroxine (l-T4)-induced thyrotoxicosis in rats. Administration of l-T4 at 500µg/kg body weight for 12days increased the levels of serum thyroid hormones, the activity of 5'-monodeiodinase-I (5'DI) and hepatic glucose-6-phosphatase (G-6Pase) as well as lipid peroxidation (LPO); with a parallel decrease in the levels of cellular antioxidants and serum lipids. However, administration of the isolated THDMF-Rha at a pre-standardized dose for 15days ameliorated the l-T4-induced alterations in the levels of thyroid hormones, hepatic LPO, G-6-Pase, 5'DI activity, and cellular levels of antioxidants and improved the status of different serum lipids, suggesting its antithyroidal and antioxidative potential. As compared to standard antithyroid drug, propylthiouracil, THDMF-Rha appeared to be more promising.

Coexistence of Graves' disease and unilateral functioning Struma ovarii: a case report.

BACKGROUND: Coexisting of Graves' disease and functioning struma ovarii is a rare condition. Although the histology of struma ovarii predominantly composed of thyrocytes, the majority of the patients did not have thyrotoxicosis. The mechanism underlying the functioning status of the tumor is still unclear but the presence of thyroid stimulating hormone receptor (TSHR) is thought to play a role. Here we describe the patient presentation and report the TSHR expression of the tumor. CASE PRESENTATION: A 56-year old Asian woman presented with long standing thyrotoxicosis for 23 years. She was diagnosed with Graves' disease and thyroid nodules. She had bilateral exophthalmos and had high titer of plasma TSHR antibody. Total thyroidectomy was performed and the histologic findings confirmed the clinical diagnosis. The patient had persistent thyrotoxicosis postoperatively. Thyroid uptake demonstrated the adequacy of the thyroid surgery and the whole body scan confirmed the presence of functioning thyroid tissue at pelvic area. The surgery was scheduled and the patient had hypothyroidism after the surgery. The pathological diagnosis was struma ovarii at right ovary. We performed TSHR staining in both the patient's struma ovarii and in 3 cases of non-functioning struma ovarii. The staining results were all positive and the intensity of the TSHR staining of functioning struma ovarii was the same as that in other cases of non-functioning tumors, suggesting that the determinant of functioning struma ovarii might be the presence of TSHR stimuli rather than the intensity of the TSHR in the ovarian tissue. CONCLUSION: In patients with Graves' disease with persistent or recurrent thyrotoxicosis after adequate ablative treatment, the possibility of ectopic thyroid hormone production should be considered. TSHR expression is found in patients with functioning and non-functioning struma ovarii and cannot solely be used to determine the functioning status of the tumor.

Reactive oxygen species play a role in muscle wasting during thyrotoxicosis.

The role of reactive oxygen species (ROS) in muscle protein hydrolysis and protein oxidation in thyrotoxicosis has not been explored. This study indicates that ROS play a role in skeletal muscle wasting pathways in thyrotoxicosis. Two experimental groups (rats) were treated for 5 days with either 3,3',5-triiodothyronine (HT) or HT with α-tocopherol (HT + αT). Two controls were used, vehicle (Control) and control treated with αT (Control + αT). Serum T3, peritoneal fat, serum glycerol, muscle and body weight, temperature, mitochondrial metabolism (cytochrome c oxidase activity), oxidative stress parameters and proteolytic activities were examined. High body temperature induced by HT returned to normal when animals were treated with αT, although total body and muscle weight did not. An increase in lipolysis was observed in the HT + αT group, as peritoneal fat decreased significantly together with an increase in serum glycerol. GSH, GSSG and total radical-trapping antioxidant parameter (TRAP) decreased and catalase activity increased in the HT group. The glutathione redox ratio was higher in HT + αT than in both HT and Control + αT groups. Carbonyl proteins, AOPP, mitochondrial and chymotrypsin-like proteolytic activities were higher in the HT group than in the Control. HT treatment with αT restored mitochondrial metabolism, TRAP, carbonyl protein, chymotrypsin-like activity and AOPP to the level as that of the Control + αT. Calpain activity was lower in the HT + αT group than in HT and Control + αT and superoxide dismutase (SOD) activity was higher in the HT + αT group than in the Control + αT. Although αT did not reverse muscle loss, ROS was involved in proteolysis to some degree.

[Distribution of IgG subclasses of TgAb and TPOAb in sera from patients with Graves' disease, Graves' disease plus Hashimoto's thyroiditis and Hashimoto's thyrotoxicosis].

OBJECTIVE: To evaluate the distribution of IgG subclasses of TgAb and TPOAb in sera from patients with Graves' disease (GD), Graves' disease plus Hashimoto's thyroiditis (GH) and Hashimoto's thyrotoxicosis. METHODS: Patients with GD (n = 33), GH (n = 31) or Hashimoto's thyrotoxicosis (n = 18) diagnosed by fine needle aspiration cytology at Department of Endocrinology of Peking University First Hospital, Beijing Haidian Hospital, China-Japan Friendship Hospital and Civil Aviation General Hospital during the period from January 2010 to May 2013 were enrolled. All of them had TgAb and TPOAb. The total serum IgG and IgG subclasses of TgAb and TPOAb were detected by antigen-specific enzyme-linked immunosorbent assay (ELISA). The prevalence and relative amount of IgG subclasses were calculated and compared among three groups. RESULTS: The levels of TRAb in GD group (21.80(7.53, 40) U/L) were significantly higher than those in GH (7.30(3.10, 25.40) U/L) (P = 0.000) and Hashimoto's thyrotoxicosis groups (4.90(1.69, 16.43) U/L) (P = 0.003). And no significant differences were found in the levels of TgAb and TPOAb. The prevalence of TgAb IgG3 subclass in Hashimoto's thyrotoxicosis group (66.7%) was higher than GD group (35.5%) and GH group (36.4%) and the difference was close to significance (P = 0.066). There were significant differences of relative amount of TgAb IgG2 and TgAb IgG4 among three groups (P = 0.039 and 0.013), and GD patients had higher relative amounts of TgAb IgG2 (0.59(0.34, 0.94)) and TgAb IgG4 (0.57(0.28, 0.97)) than GH patients (TgAb IgG2, 0.31(0.23, 0.34); TgAb IgG4, 0.26(0.09, 0.48)) or patients with Hashimoto's thyrotoxicosis (TgAb IgG2, 0.32(0.24, 0.83); TgAb IgG4, 0.33(0.10, 0.65)) (for TgAb IgG2, P = 0.009 and 0.167; for TgAb IgG4, P = 0.005 and 0.041 respectively). No significant difference was found in the prevalence of each TPOAb IgG subclass. The difference of relative amount of TPOAb IgG2 among three groups was close to significance (P = 0.069). And the relative amount was higher in sera from GD patients (0.39 ± 0.04) than that in GH patients (0.29 ± 0.13) or patients with Hashimoto's thyrotoxicosis (0.26 ± 0.02) (P = 0.104 and 0.002 respectively). CONCLUSION: The patients with high levels of TgAb IgG2, TgAb IgG4 and TPOAb IgG2 subclasses have a greater risk of GD. The IgG subclass distribution of TgAb and TPOAb might help to differentiate the causes of thyrotoxicosis in autoimmune thyroid diseases.

[Experience of using phytopreparation Alba (root extract of the Potentilla alba) in complex treatment of thyroid pathology in children and adolescents].

This article presents the background for including phytopreparation Alba (root extract of the Potentilla alba) into complex treatment of thyroid pathology. The findings confirm visible reduction of size of the thyroid gland and normalizing its functions in children and adults with the thyroid gland with normal or enhanced function treated by Alba per oral.

Bone disease in thyrotoxicosis.

Thyrotoxicosis, a clinical syndrome characterized by manifestations of excess thyroid hormone, is one of the commonly-recognised conditions of the thyroid gland. Thyrotoxicosis causes acceleration of bone remodelling and though it is one of the known risk factors for osteoporosis, the metabolic effects of thyroxine on bone are not well discussed. Studies show that thyroid hormones have effects on bone, both in vitro and in vivo. Treatment of thyrotoxicosis leads to reversal of bone loss and metabolic alterations, and decreases the fracture risk. There are limited studies in India as to whether these changes are fully reversible. In this review we discuss about the effects of thyrotoxicosis (endogenous and exogenous) on bone and mineral metabolism, effects of subclinical thyrotoxicosis on bone and mineral metabolism and effects of various forms of treatment in improving the bone mineral density in thyrotoxicosis.

Irbesartan prevents myocardial remodeling in experimental thyrotoxic cardiomyopathy.

This study evaluated the effects of irbesartan and propranolol on thyroid hormone (TH)-induced cardiac functional and structural remodeling. A rat model of thyrotoxicosis was established by daily intraperitoneal injections of L-thyroxine (T(4), 100 µg/kg) for 4 weeks. Forty Sprague-Dawley rats were randomly divided into four groups (n = 10 each): control group, T(4) group (T(4) alone), T(4) plus irbesartan group (T(4)-Irb, 30 mg/kg), and T(4) plus propranolol group (T(4)-Pro, 0.5mg/mL of drinking water). Cardiac chamber size and functional parameters were measured by echocardiography and cardiomyocyte diameter. Heart rate (HR) and cardiac fibrosis were determined. T(4) alone showed significantly increased HR and cardiomyocyte width (25.0 ± 1.77 vs. 18.8 ± 0.84 µm, P < 0.001) with fibrosis, reduced left ventricle (LV) longitudinal strain (S(long); -16.0 ± 6.27 vs. -22.7 ± 5.19 %, P < 0.001) compared with control. When compared with T(4) alone, T(4)-Irb showed significantly improved LV S(long) (-21.4 ± 1.84 vs. -16.0 ± 6.27 %, P =0.017) and reduced cardiomyocyte width (21.0 ± 1.0 vs. 25.0 ± 1.77 µm, P =0.002) with comparable HR (458.4 ± 24.3 vs. 486.6 ± 30.1 bpm, P = 0.086). However, T(4)-Pro showed significantly reduced HR with improved LV S(long) without alteration of cardiomyocyte width and fibrosis compared with T(4) alone. In conclusion, renin-angiotensin system (RAS) blocking by irbesartan could significantly attenuate TH-induced cardiac structural and functional remodeling. However, HR reduction by propranolol could not alternate structural remodeling, which may implicate the RAS as having an important role in thyrotoxic cardiomyopathy beyond tachycardia.

Surgical treatment for thyrotoxic hypokalemic periodic paralysis: case report.

Thyrotoxic hypokalemic periodic paralysis (THPP) is a rare, potentially life-threatening endocrine emergency. It is characterized by recurrent muscle weakness and hypokalemia. Because many THPP patients do not have obvious symptoms and signs of hyperthyroidism, misdiagnosis may occur. The published studies revealed that definitive therapy for THPP is control of hyperthyroidism by medical therapy, radioactive iodine or surgery, but the long-term post-operative follow-up result was not observed. We reported two cases of medically refractory THPP with recurrent paralysis of extremities and hypokalemia, and both were combined with thyroid nodules. Both patients were treated with total thyroidectomy; the pathology revealed that one is Graves' disease with thyroid papillary carcinoma, and the other is adenomatous goiter with papillary hyperplasia. No episode of periodic paralysis was noted and laboratory evaluation revealed normal potassium level during the post-operative follow up. Our experience suggests that total thyroidectomy by experienced surgeon is an appropriate and definite treatment for medically refractory THPP, especially in cases combined with thyroid nodules.

[Application of herbal medicine alba in treatment of patients with the pathology of thyroid].

High prevalence of hyperplastic and autoimmune diseases of thyroid in Ukrainian population is determined by endemic deficit of iodine and selenium. The aim of this research was to assess the place of biologically-active additions on the basis of herbal material containing an iodine and selenium in prophylaxis and treatment of thyroid pathology. During the six month period 55 patients received herbal preparation Alba twice a day. The levels of TSH, volume of thyroid, the sizes of nodular goiter (ultrasound investigation) were measured before and at the end of the investigation. The levels of thyroid stimulating antibodies to TSH receptor (AB-r TSH) were evaluated in patients with hyperthyroidism. The results of Alba application showed that in patients with thyroid pathology (diffuse nontoxic goiter, hyperthyroidism and chronic thyroiditis) it was possible to reduce the volume of thyroid, normalize its function, and decrease the level of AB-r TSH in diffuse toxic goiter. We also found approximately 20 % shortening of the time needed to get target level of TSH and finally the duration of treatment of thyrotoxicosis.