[A clinical study on gestational transient thyrotoxicosis]

OBJECTIVE

To investigate the prevalence of gestational transient thyrotoxicosis (GTT) and analyze the cause of thyrotoxicosis encountered in this period.

METHODS

An epidemiologic survey in ten hospitals in Shenyang was performed and 534 pregnant women during the first trimester of pregnancy filled questionnaire, received physical examination and had serum thyroid-stimulating hormone (TSH), free T(4) (FT(4)), free T(3) (FT(3)), thyroid peroxidase antibody (TPOAb), thyrotrophin receptor antibody (TRAb), and human chorionic gonadotrophin (hCG) tests.

RESULTS

(1) The total prevalence of thyrotoxicosis was 9.75% (52/534) in the first trimester and the prevalence of GTT was 7.86%, which accounted for 80.77% of the thyrotoxicosis encountered in this period. A total of 88.89% of the overt GTT showed only elevated FT(3) level. (2) The level of serum hCG increased gradually in the first trimester. The medians of hCG were 25 300, 85 220 and 81 780 IU/L 6, 8 - 10 and 12 weeks after gestation, respectively (P = 0.000). The medians of serum TSH were 1.45, 1.10 and 0.84 mIU/L 6, 8 - 10 and 12 weeks after gestation, respectively (P < 0.01). (3) When serum hCG was more than 50 000 IU/L, the prevalence of GTT increased obviously. When serum hCG was between 80 000 IU/L and 110 000 IU/L, subclinical GTT increased significantly. When serum hCG was more than 110 000 IU/L, overt GTT increased significantly. Correlation analysis showed that serum hCG was related negatively with TSH (r = -0.402, P = 0.000) and positively with FT(3) (r = 0.165, P = 0.000), but not related with FT(4).

CONCLUSIONS

The prevalence of GTT is 7.86% in the first trimester and it is the main cause of thyrotoxicosis found in the first trimester, accounting for 80.77% of all the causes. The serological characteristic of overt GTT is mainly the elevation of serum FT(3) level. Serum hCG level is related with the severity of GTT.

Thyrotoxicosis during sunitinib treatment for renal cell carcinoma

CONTEXT

Sunitinib malate is an oral tyrosine kinase inhibitor used in the treatment of renal cell carcinoma (RCC) and gastrointestinal stromal tumours. Hypothyroidism has been observed in patients treated with sunitinib, but the mechanism whereby sunitinib induces hypothyroidism is unknown.

OBJECTIVE

To describe a series of six patients who developed thyrotoxicosis while on sunitinib for metastatic RCC.

SETTING

The study was conducted at Austin Health, a tertiary teaching hospital in Melbourne, Australia.

RESULTS

Two patients developed severe thyrotoxicosis within 10 weeks after commencing sunitinib. In contrast, in the four patients who presented with later onset (16-30 weeks) thyrotoxicosis, the thyrotoxicosis was relatively mild, self-limiting and rapidly progressed to hypothyroidism. These patients experienced recurrent episodes of thyrotoxicosis in temporal relation to their cyclical sunitinib treatment. One patient had cytological evidence of lymphocytic thyroiditis.

CONCLUSIONS

These findings suggest that sunitinib-induced hypothyroidism may be a consequence of preceding thyroiditis with associated transient thyrotoxicosis. As predictive factors are currently unknown, we suggest regular monitoring of thyroid function in all patients commenced on sunitinib. Clinicians treating patients with sunitinib or other similar kinase inhibitors should to be alerted to thyroid dysfunction as a potential toxicity of these agents.

Thyrotoxic periodic paralysis admitted to the medical department in Qatar

OBJECTIVES

In this study we describe the clinical presentation and electrolyte disturbances of thyrotoxic periodic paralysis (TPP) in patients admitted to the Department of Medicine at Hamad General Hospital.

METHODS

Retrospective descriptive study involving patients admitted to the medical department of Hamad General Hospital with paralysis and hyperthyroidism.

RESULTS

Eighteen patients with TPP were identified over a three-year period (2004-2007). Their mean age was 32.4 +/- 8.52 years (range 21 to 48 years); all were males. Eleven patients were from the Philippines, five were from Nepal, one was Indian and one was from Sri Lanka. Fourteen patients (77.8%) had the attack in the summer while the remaining four in winter. Nine had a history of severe exertion, five had ingested a heavy carbohydrate meal, two had a sore throat, one had ingested alcoholic and one was without a precipitating cause. Fifteen patients had no previous history of hyperthyroidism. Later on, all patients proved to have hyperthyroidism. All patients were hypokalaemic, while seven patients had hypophosphataemia and three had hypomagnesaemia. Urinary potassium was <20 mmol/l in all patients. Fifteen patients had ECG changes. All patients had proximal myopathy. Twelve patients had signs of hyperthyroidism in the form of goitre, warm sweaty palms, tachycardia, and tremor. Nine patients had attacks of paralysis before diagnosis. After discharge, ten patients had recurrences within one to seven months.

CONCLUSION

The causes of hypokalaemia and lower-extremity paralysis are numerous; TPP should be taken into consideration in the differential diagnosis of all acute episodes of motor paralysis, especially in young Asian male patients.

Autonomic nervous system function in chronic exogenous subclinical thyrotoxicosis and the effect of restoring euthyroidism

CONTEXT

Knowledge on the relationship between the autonomic nervous system and subclinical hyperthyroidism is mainly based upon cross-sectional studies in heterogeneous patient populations, and the effect of restoration to euthyroidism in subclinical hyperthyroidism has not been studied.

OBJECTIVE

We investigated the long-term effects of exogenous subclinical hyperthyroidism on the autonomic nervous system and the potential effects of restoration of euthyroidism.

DESIGN

This was a prospective single-blinded, placebo-controlled, randomized trial.

SETTING

The study was performed at a university hospital.

PATIENTS

A total of 25 patients who were on more than 10-yr TSH suppressive therapy after thyroidectomy was examined.

INTERVENTION

Patients were studied at baseline and subsequently randomized to a 6-month thyroid hormone substitution regimen to obtain either euthyroidism or maintenance of the subclinical hyperthyroid state.

MAIN OUTCOME MEASURES

Urinary excretion of catecholamines and heart rate variability were measured. Baseline data of the subclinical hyperthyroidism patients were compared with data obtained in patients with hyperthyroidism and controls.

RESULTS

Urinary excretion of norepinephrine and vanillylmandelic acid was higher in the subclinical hyperthyroidism patients compared with controls and lower compared with patients with overt hyperthyroidism. Heart rate variability was lower in patients with hyperthyroidism, intermediate in subclinical hyperthyroidism patients, and highest in the healthy controls. No differences were observed after restoration of euthyroidism.

CONCLUSIONS

Long-term exogenous subclinical hyperthyroidism has effects on the autonomic nervous system measured by heart rate variability and urinary catecholamine excretion. No differences were observed after restoration to euthyroidism. This may indicate the occurrence of irreversible changes or adaptation during long-term exposure to excess thyroid hormone that is not remedied by 6-month euthyroidism.

Goserelin-induced transient thyrotoxicosis in a hypothyroid woman on L-thyroxine replacement

An increase in free thyroxine (fT4) and a decrease in thyroid-stimulating hormone (TSH) was observed in a hypothyroid woman on levothyroxine treatment after implantation of goserelin, a gonadotropin-releasing hormone (GnRH) analogue. In the literature no data are available that describe a drug interaction between GnRH analogues and thyroid hormone replacement. Our hypothesis to explain this observation is that goserelin decreased serum thyroxine-binding-globulin (TBG), resulting in an increase in fT4 and thereby a decrease in serum TSH.

[Safety of surgical interventions on the thyroid gland and anesthesia against the background of thyrotoxicosis]

Results of surgical treatment of 192 patients aged from 19 through 72 years were analyzed, they had euthyroid goiter, compensated and subcompensated forms of toxic goiter. A comparative assessment is given of sodium thiopental, propophol and sibazon for induction of general anesthesia according to their effects on the indices of central hemodynamics, thyroid status and subjective patient's comfort, as well as propranolol, thalinolol and esmolol as medicines for intraoperative correction of hemodynamic manifestations of thyrotoxicosis. The influence of surgical manipulations was assessed on main hemodynamic indices and the level of thyroid glands hormones. Attention is called to the main tasks of anesthesiologists responsible for anesthesiological maintenance of operation under conditions of compensated and subcompensated thyrotoxicosis.

The prevalence of transient thyrotoxicosis after antithyroid drug therapy in patients with Graves' disease

BACKGROUND

Although transient thyrotoxicosis occurring after antithyroid drug (ATD) withdrawal in patients with Graves' hyperthyroidism has been reported, the prevalence of transient thyrotoxicosis after ATD therapy is as yet unknown. When patients with transient hyperthyroidism are mistakenly regarded as recurrences, they receive unnecessary therapy. The aim of this study was to investigate the prevalence of transient thyrotoxicosis after ATD withdrawal.

METHODS

We selected 110 consecutive patients with Graves' disease whose ATD therapy was stopped from December 2002 to September 2004 prospectively. Patients were observed for more than 1 year after ATD withdrawal, and 12 patients dropped out. Serum levels of free thyroxine (FT(4)), thyrotropin, and thyrotropin-binding inhibitor immunoglobulin were measured at ATD withdrawal, and 3, 6, and 12 months after withdrawal. When the patients showed mild thyrotoxicosis (serum FT(4) level of less than 3.00 ng/dL), we followed them up for 1 month without medication.

RESULTS

The remission rate of the study group was 61.8% (68/110). Twenty-eight patients became euthyroid after transient thyrotoxicosis, equivalent to 41.2% of the remission patients. Eight of 28 patients showed overt thyrotoxicosis, and the rest subclinical thyrotoxicosis. Transient thyrotoxicosis occurred mostly 3-6 months after ATD withdrawal.

CONCLUSIONS

Transient thyrotoxicosis after ATD withdrawal in patients with Graves' disease is not a rare phenomenon. Clinicians should be aware that the recurrence of Graves' disease after the withdrawal of ATD may be transient.

[Melatonin influence on free radical homeostasis in rat tissues at thyrotoxicosis]

Experimental thyrotoxicosis in rats is accompanied by the increase of serum alanine aminotransferase (AlA), aspartate aminotransferase (AsA), creatine kinase-MB (CK-MB) activities and content of primary products of lipid peroxidation--conjugated dienes--in liver, heart and blood. This suggests impairments in these organs accompanying free radical processes intensification. Administration of melatonin decreased AlA, AsA and CK-MB activities and CD level decreased. Thyrotoxicosis increased catalase activity in liver, heart and blood. Exogenous melatonin decreased specific activity ofcatalase in blood and in heart in comparison with animals subjected to hyperthyroidism. However, some increase of catalase specific activity (approximately 15%) was observed in liver. alpha-Tocopherol content, raising in rat tissues in thyrotoxicosis development conditions, decreased after melatonin treatment. Thus, exogenous melatonin is capable to reduce lipid peroxidation intensity at thyrotoxicosis and to act as an adoptogen, regulating free radical homeostasis.

Atrial fibrillation induced by post-parathyroidectomy transient thyrotoxicosis

We describe a 59-year-old Japanese woman with post-parathyroidectomy transient thyrotoxicosis and atrial fibrillation. She underwent parathyroidectomy for secondary hyperparathyroidism due to chronic renal failure. Three days after surgery, she complained of palpitation and chest pain due to atrial fibrillation. Results of thyroid function tests were compatible with thyrotoxicosis. Twelve days after parathyroidectomy, the elevated level of free thyroxine decreased spontaneously to the normal range. These features were compatible with post-parathyroidectomy transient thyrotoxicosis. No further recurrences of thyrotoxicosis or atrial fibrillation were observed for one year. This is the first report of atrial fibrillation induced by post-parathyroidectomy transient thyrotoxicosis.

Total intravenous anesthesia for evacuation of a hydatidiform mole and termination of pregnancy in a patient with thyrotoxicosis

Clinical hyperthyroidism is found in approximately 5% of women with a hydatidiform mole, as human chorionic gonadotropin secreted by molar tissue is structurally similar to thyroid-stimulating hormone. A hydatidiform mole occasionally presents with a co-existing viable fetus. Surgical evacuation may be indicated for significant hemorrhage or preeclampsia. Perioperative management in the presence of hyperthyroidism may be complicated by a thyroid storm. We report a case of total intravenous anesthesia with propofol and remifentanil, combined with an esmolol infusion, to control sympathetic hyperactivity during surgery.

Thyroid dysfunction in perimenopausal and postmenopausal women

Thyroid dysfunction is common, especially among women over the age of 50. In caring for peri- and post-menopausal women, it is important to recognize the changing clinical manifestations of thyroid disease with age. Postmenopausal women are at increased risk of both osteoporosis and cardiovascular disease, and untreated thyroid disease may exacerbate these risks. Screening for thyroid dysfunction in asymptomatic individuals is controversial, but aggressive case-finding should be pursued, especially in older women. Women with overt thyroid dysfunction should be treated. Therapy for women with subclinical thyroid dysfunction is more controversial, although women with levels of thyroid stimulating hormone (TSH) > or =10 mU/L should be treated, and treatment may be considered in symptomatic women with subclinical hypothyroidism and TSH values <10 mU/L, and in women with subclinical hyperthyroidism who have TSH values consistently <0.1 mU/L. In women who are treated with thyroxine, careful dose titration and monitoring are required in order to prevent the adverse consequences of iatrogenic subclinical hyperthyroidism or hypothyroidism. Finally, caution is required in diagnosing and treating thyroid dysfunction in women who are taking oral estrogens or selective estrogen receptor modulators.

[Erythrocyte carbonic anhydrase I and zinc concentrations in thyrotoxicosis reflect integrated thyroid hormone levels over the previous few months]

In the present review, the clinical utility of determining red blood cell (RBC) carbonic anhydrase I isozyme (CA1) and zinc(Zn) concentrations in patients with various forms of thyroid disease is discussed. RBC CAI and Zn concentrations were both decreased in patients with hyperthyroid Graves' disease. After treatment, the normalization of RBC CA1 and Zn lagged two months behind the normalization of plasma thyroxine (T4) and triiodothyronine (T3) levels. Furthermore, the highest correlation coefficients were observed between RBC CA1 and Zn levels, and plasma thyroid hormone levels measured eight weeks earlier. These results indicate that both RBC CAI and zinc levels reflect integrated plasma thyroid hormone levels over the previous few months. Transient thyrotoxicosis due to destructive thyroiditis did not cause significant changes in RBC CA1 and Zn concentrations. T3 at a physiological free concentration significantly decreased the level of CAl mRNA and the concentration of CA1 in burst forming unit erythroid-derived cells. These results indicate that the measurement of RBC CA1 and Zn concentrations may be useful as follows: (1) to obtain an accurate estimate of the extent of elevated thyroid hormone levels in hyperthyroid patients in whom serial measurements were not obtained over time; (2) to differentiate patients with hyperthyroid Graves' disease from those with transient thyrotoxicosis.

Plasma adrenocorticotropin (ACTH) values and cortisol response to 250 and 1 microg ACTH stimulation in patients with hyperthyroidism before and after carbimazole therapy: case-control comparative study

CONTEXT

Although the production and metabolic clearance rate of cortisol is increased during thyrotoxic state, the net effect on adrenocortical reserves is not clear.

OBJECTIVE

We assessed circulating ACTH levels, cortisol binding globulin (CBG), and adrenocortical reserves in hyperthyroid patients (before and after carbimazole therapy) and healthy controls.

DESIGN AND SETTING

This was a case-control investigative study in a tertiary care setting.

PATIENTS AND METHODS

Plasma ACTH and free cortisol index (FCI; serum cortisol/CBG) were measured in 49 consecutive patients with hyperthyroidism and 50 controls. ACTH(1-24) stimulation tests (250 and 1 microg) were carried out in the first 29 patients and 15 controls. Peak FCI less than the mean -3 sd of healthy controls was considered subnormal. ACTH(1-24) stimulation tests were repeated in 24 patients in the euthyroid state.

RESULTS

The mean basal plasma ACTH and FCI were higher and CBG was lower in thyrotoxic patients in comparison with controls. The peak cortisol was less than 18 microg/dl in 10 of 29 and 14 of 29 on 250 and 1 microg ACTH(1-24) stimulation. Peak FCI was subnormal only in three of 27 (11.1%) and two of 21 (7.4%) on 250 and 1 microg ACTH(1-24) stimulation, respectively. The mean plasma ACTH, basal FCI, and subnormal peak FCI (two of the three) normalized after euthyroidism. Plasma ACTH and FCI did not correlate with severity of thyrotoxicosis.

CONCLUSIONS

Up to 11% of thyrotoxics have subnormal peak FCI on ACTH(1-24) stimulation. Such changes occur despite high basal plasma ACTH and FCI. Use of FCI, rather than total cortisol, is required for the interpretation of cortisol values in thyrotoxicosis due to the variation in CBG.

Which criterion of intraoperative iPTH assay is the most accurate in prediction of true serum calcium levels after thyroid surgery?

BACKGROUND AND AIMS

Intraoperative quick intact parathyroid hormone (iPTH) assay (IOPTH) has become a valuable adjunct in parathyroid surgery reliably predicting cure from hyperparathyroid state. Similarly to parathyroid surgery, the accuracy of the assay in predicting postoperative calcemia after thyroid surgery is related to blood sample timing and the criteria applied with no guidelines widely accepted, so far. This study compares different IOPTH criteria in predicting hypoparathyroidism-related hypocalcemia after thyroid surgery.

MATERIALS AND METHODS

The study included 200 consecutive patients undergoing total thyroidectomy. Three blood samples for IOPTH were taken in each patient: preoperatively--baseline (BL), at the end of surgery--skin closure (SC), and at 4 h postoperatively (4H). Serum calcium was routinely monitored at 4, 12, 24, 48, and 72 h postoperatively. The incidence and severity of hypocalcemia and related symptoms were matched to IOPTH results. The following criteria were tested: A, greater than 50% drop from BL at SC; B, greater than 70% drop from BL at SC; C, greater than 50% drop from BL at 4H; D, greater than 70% drop from BL at 4H; E, serum iPTH less than 15 pg/ml at SC; F, serum iPTH less than 10 pg/ml at SC; G, serum iPTH less than 15 pg/ml at 4H; H, serum iPTH less than 10 pg/ml at 4H. The accuracy of the tested criteria was calculated in predicting serum calcium level less than 2.0 mmol/l at any point after thyroidectomy.

RESULTS

Tested criteria had the following value in predicting serum calcium level less than 2.0 mmol/l after thyroidectomy (sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy, respectively): A (60, 89, 38, 95, and 86%), B (80, 93, 57, 98, and 92%), C (70, 90, 44, 96, and 88%), D (85, 95, 65, 98, and 94%), E (80, 91, 50, 98, and 90%), F (90, 95, 69, 99, and 95%), G (90, 95, 70, 99, and 95%), H (95, 99, 90, 99, and 98%).

CONCLUSIONS

The criterion of iPTH serum level less than 10 pg/ml at 4 h postoperatively has the highest accuracy in predicting serum calcium level below 2.0 mmol/l after total thyroidectomy when compared with the other criteria.

Soluble CTLA-4 in autoimmune thyroid diseases: relationship with clinical status and possible role in the immune response dysregulation

CTLA-4 molecule, expressed by activated T and B lymphocytes, transduces an inhibitory signal. Increasing evidence showed CTLA-4 gene as an important susceptibility locus for autoimmune endocrinopathies and other autoimmune disorders. The aim is to evaluate the augmented sCTLA-4 serum levels in different autoimmune thyroid diseases when compared with normal donors or with non-autoimmune hyperthyroidism and to investigate the functional activities and suggest the possible pathogenetic role of sCTLA-4. We demonstrate the presence of a soluble form of CTLA-4 in 59/90 sera from patients with autoimmune thyroid diseases (both Graves' disease and autoimmune thyroiditis). sCTLA-4 levels were not related to specific clinical manifestations, such as clinical thyroid status (hypo- or hyperthyroidism), circulating thyroid hormones, or other clinical features (ophthalmopathy). sCTLA-4 production does not seem to be affected by disease evolution during time. We showed that sCTLA-4 from sera of patients with thyroid autoimmunity is able to bind its physiological ligands CD80/CD86 and displays functional activities on different in vitro systems (T-cell proliferation induced by specific soluble antigens, bi-directional mixed lymphocyte reaction). In conclusion, we demonstrate an increment of sCTLA-4 in serum of patients with autoimmune thyroid diseases. Its possible pathogenetic role during autoimmune processes can be speculated: sCTLA-4 can specifically inhibit the early T-cell activation by blocking the interaction of CD80/CD86 with the co-stimulatory receptor CD28. Conversely, higher levels of sCTLA-4 could compete with membrane-bound CTLA-4 for CD80/CD86, in later T lymphocytes activation phase, causing a reduction of inhibitory signaling.

Thyrotoxicosis with coronary spasm that required coronary artery bypass surgery

We describe a 47-year-old woman with severe coronary vasospasm induced by hyperthyroidism. The patient complained of anginal chest pain without specific characteristics of thyrotoxicosis. Coronary arteriography was performed and revealed 90% stenosis of both the left and right coronary os. She was treated with emergent coronary artery bypass graft surgery. Postoperatively, she exhibited a comatose mentality. Severe thyrotoxicosis was indicated on thyroid function tests and thyrotoxic storm was diagnosed. Nineteen days after the surgery and following the initiation of propylthiouracil treatment, coronary arteriography revealed entirely normal coronary arteries.

Heart failure caused by thyrotoxicosis in pregnancy--case report

PURPOSE OF INVESTIGATION

To emphasize the importance of untreated thyrotoxicosis in pregnancy. When left untreated, severe maternal, fetal and even neonatal adverse outcomes such as preeclampsia, premature labor, low birthweight infants and increased perinatal mortality are prone to complicate the pregnancy.

PRESENTATION

A case of thyrotoxicosis untreated during pregnancy is reported.

CONCLUSION

Many authors have concluded that there is no need for routine assessment of the thyroid hormones and TSH levels in pregnancy. Nonetheless laboratory assessment for thyrotoxicosis should be done in cases with suspicious symptoms and signs. All thyrotoxic women should also be under treatment during pregnancy. Early diagnosis and/or control of hyperthyroidism would decrease the incidence of complications during pregnancy.

Continued suppression of serum TSH level may be attributed to TSH receptor antibody activity as well as the severity of thyrotoxicosis and the time to recovery of thyroid hormone in treated euthyroid Graves' patients

The cause of continued suppression of serum thyroid-stimulating hormone (TSH) levels during antithyroid drug therapy in some Graves' patients is unclear. Recently, there has been a notable explanation involving the direct inhibition of TSH receptor antibody (TRAb) on TSH secretion in the pituitary gland. The purpose of this study is to verify the relation between TRAb or other clinical parameters and the continued suppression of serum TSH level during antithyroid drug therapy in patients with Graves' disease. We reviewed the medical records of patients with Graves' disease between 1995 and 2002 at Samsung Medical Center. We selected 167 Graves' patients who had been euthyroid for at least 12 months after recovery of serum T3 and T4 levels during the antithyroid drug therapy. We analyzed the correlation of the interval until recovery of serum TSH with the pretreatment clinical parameters. We compared the recovery rates of suppressed TSH levels between pretreatment thyrotrophin-binding inhibitory immunoglobulin (TBII)-positive (>15%) and TBII-negative patients. We also compared the clinical parameters between two groups at the time of diagnosis and after recovery of thyroid hormone. Pretreatment serum T3 level, (131)I uptake, TBII activity, and the time to recovery of T3 or T4/free T4 level showed significant positive correlations with the interval until recovery of serum TSH level ( p < 0.05). Recovery rates of serum TSH levels at 3 months after recovery of thyroid hormone were significantly lower in pretreatment TBII-positive patients than those in TBII-negative patients ( p < 0.01). Serum TSH levels were significantly lower in TBII-positive patients at 3 months after recovery of thyroid hormone ( p < 0.05). TBII activities inversely correlated only with serum TSH levels at 3months after recovery of thyroid hormone ( p < 0.001). In conclusion, continued suppression of serum TSH level may be attributed to TRAb activity as well as the pretreatment severity of thyrotoxicosis and the time to recovery of thyroid hormone in patients with Graves' disease during antithyroid drug therapy.

Combination of minimally invasive thyroid surgery and local anesthesia associated to iopanoic acid for patients with amiodarone-induced thyrotoxicosis and severe cardiac disorders: a pilot study

BACKGROUND AND AIMS

Amiodarone-induced thyrotoxicosis is a life-threatening condition. A prompt control of thyrotoxicosis is obtained by thyroidectomy. Preparation with iopanoic acid proved to be very effective in reducing cardiovascular complications. Nevertheless, general anesthesia and extensive surgery may affect negatively patients also after adequate preparation. Safety and efficacy of minimally invasive video-assisted thyroidectomy performed under regional anesthesia (bilateral modified deep cervical block) in patients with amiodarone-induced thyrotoxicosis was evaluated.

PATIENTS AND METHODS

Eight patients with amiodarone-induced thyrotoxicosis (three with type I and five with type II), mean age 66.2 years, were prepared with iopanoic acid. There were five men and three women. Three patients had dilatative cardiomyopathy, three had heart failure secondary to severe myocardial infarction, and two had refractory unstable rhythm disorders.

RESULTS

Minimally invasive video-assisted thyroidectomy was performed under regional anesthesia. Mean operative time was 55.5 min. During surgery, lung and heart function remained well and no surgical complications occurred. After surgery, all patients remained on amiodarone therapy and two patients were subsequently removed from the checklist for heart transplantation.

CONCLUSION

Minimally invasive video-assisted thyroidectomy under regional anesthesia can be proposed as resolution of amiodarone-induced thyrotoxicosis in high risk patients with severe cardiac disorders, after preparation with iopanoic acid.

Amiodarone-induced thyroid dysfunction in clinical practice

Amiodarone is a potent class III anti-arrhythmic drug used in clinical practice for the prophylaxis and treatment of many cardiac rhythm disturbances, ranging from paroxismal atrial fibrillation to life threatening ventricular tachyarrhythmias. Amiodarone often causes changes in thyroid function tests mainly related to the inhibition of 5'-deiodinase activity resulting in a decrease in the generation of T3 from T4 with a consequent increase in rT3 production and a decrease in its clearance. In a group of amiodarone-treated patients there is overt thyroid dysfunction, either amiodarone-induced thyrotoxicosis (AIT) or amiodarone-induced hypothyroidism (AIH). AIT is primarily related to excess iodine-induced thyroid hormone synthesis in an abnormal thyroid gland (type I AIT) or to amiodarone-related destructive thyroiditis (type II AIT). The pathogenesis of AIH is related to a failure to escape from the acute Wolff-Chaikoff effect due to defects in thyroid hormonogenesis, or, in patients with positive thyroid autoantibody test, to concomitant Hashimoto's thyroiditis. Both AIT and AIH may develop either in apparently normal thyroid glands or in glands with preexisting, clinically silent abnormalities. AIT is more common in iodine-deficient regions of the world, whereas AIH is usually seen in iodine-sufficient areas. In contrast to AIH, AIT is a difficult condition to diagnose and treat, and discontinuation of amiodarone is usually recommended. In this review we analyse, according to data from current literature, the alterations in thyroid laboratory tests seen in euthyroid patients under treatment with amiodarone and the epidemiology and treatment options available of amiodarone-induced thyroid dysfunctions (AIT and AIH).

Early-onset thyrotoxicosis after unrelated cord blood transplantation for acute myelogenous leukemia

Thyroid dysfunction is a common complication after allogeneic hematopoietic stem cell transplantation (SCT). However, thyrotoxicosis as defined by elevated serum-free thyroxine (FT4) or free triiodothyronine (FT3) levels together with low thyroid-stimulating hormone (TSH) levels is rare after SCT. Here we describe 2 patients who developed thyrotoxicosis within the first 50 days after unrelated cord blood transplantation (CBT). Patient 1 is a 32-year-old woman with acute myelogenous leukemia (AML)-M5a who underwent CBT. On day +41, she developed tachycardia. On day +48, FT4 increased to 2.2 ng/dL and TSH was suppressed to less than 0.1 microU/mL. Antithyroid peroxidase antibody was positive. On day +83, FT4 spontaneously decreased to 1.4 ng/dL. Patient 2 is a 42-year-old man with AML-M4 who underwent CBT. On day +42, he developed tachycardia. On day +48, FT3 increased to 4.75 pg/mL and TSH was suppressed to 0.02 microU/mL. Antithyroid peroxidase antibody was positive. Eight months after CBT, his thyroid function spontaneously returned to normal. The presence of antithyroid peroxidase antibody suggested that immune-mediated reactions might be associated with the development of thyrotoxicosis after CBT in our patients. The present study shows that thyrotoxicosis can occur during very early periods after CBT.

[The effects of amiodaron on the thyroid function]

The use of several groups of medications may result in thyroid dysfunction including thyrotoxicosis or hypothyroidism of various degree (from subclinical to full-clinical syndrome). The mentioned disturbances may develop either on the basis of normal euthyroid gland or may overlap the previously-existing oceult changes (first of all different forms of autoimmune thyroiditis). Amiodarone is a widely used anti-arrythmic drug with considerable potential to cause thyroid dysfunction because of its 35% iodine content. Besides amiodarone particles are known to inhibit T4 to T3 conversion, they work as inhibitors of nuclear receptors for thyroid hormones, exert cytotoxic effect and induce immune/inflammatory process in thyroid gland. Both thyrotoxicosis (AIT - amiodarone induced thyrotoxicosis) and hypothyroidism (AIH - amiodarone induce hypothyroidism) may develop during amiodarone therapy. AIT appears to occur more frequently in geographical areas with low iodine intake, whereas AIH is more frequent in iodine-sufficient areas. Two forms of AIT are known. Their differentiation is very important for further therapeutical procedures. Because thyrotoxicosis and hypothyroidism symptoms during amiodarone therapy are scanty, there is need for periodic determination of thyroid function. Normal ranges for amiodarone patients differ from those for the rest of population. They are presented in this review. Treatment of AIT is very complicated. Sometimes there is need to use few methods together, especially when amiodarone treatment can not be stopped.

A hyperthyroid patient with measurable thyroid-stimulating hormone concentration - a trap for the unwary

INTRODUCTION

In a patient with hyperthyroidism, the detection of elevated thyroid hormone concentration with measurable thyroid-stimulating hormone (TSH) value poses considerable diagnostic difficulties.

CLINICAL PICTURE

This 38-year-old lady presented with clinical features of thyrotoxicosis. Her serum free thyroxine concentrations were unequivocally elevated [45 to 82 pmol/L (reference interval, 10 to 20 pmol/L)] but the serum TSH values were persistently within the reference interval [0.49 to 2.48 mIU/L (reference interval, 0.45 to 4.5 mIU/L)].

TREATMENT

Investigations excluded a TSH-secreting pituitary adenoma and a thyroid hormone resistance state and confirmed false elevation in serum TSH concentration due to assay interference from heterophile antibodies. The patient was treated with carbimazole for 18 months.

OUTCOME

The heterophile antibody-mediated assay interference disappeared 10 months following the initiation of treatment with carbimazole, but returned when the patient relapsed. It disappeared again 2 months after the initiation of treatment.

CONCLUSIONS

Clinicians should be aware of the potential for interference in immunoassays, and suspect it whenever the test results seem inappropriate to the patient's clinical state. Misinterpretation of test values, arising as a result of assay interference, may lead to misdiagnosis, unnecessary and at times expensive investigations, delay in initiation of treatment and worst of all, the initiation of inappropriate treatment.