A clinical and therapeutic approach to thyrotoxicosis with thyroid-stimulating hormone suppression only

Maternal subclinical hyperthyroidism and adverse pregnancy outcomes considering the iodine status: Tehran thyroid and pregnancy study

BACKGROUND

Unlike overt thyroid diseases, the impacts of subclinical thyroid dysfunction, especially subclinical hyperthyroidism (SH), on adverse pregnancy outcomes are inconclusive.

OBJECTIVE

We aimed to investigate the effect of maternal SH on adverse maternal and neonatal outcomes based on urinary iodine concentration (UIC).

METHODS

A secondary analysis was run on data collected in the Tehran Thyroid and Pregnancy study (TTPs). We used the data of 131 women with SH and 1650 cases of euthyroid. Serum levels of thyroid-stimulating hormone (TSH), thyroxine (T4), free thyroxine index (FT4I), and thyroid peroxidase antibody (TPOAb) were assessed at the first prenatal visit. A generalized linear regression model was applied to identify the effect of SH on the pregnancy outcomes based on UIC, and the effects were estimated with a 95% confidence interval.

RESULTS

Preterm delivery was observed in 12.3% of women with SH and 6.7% of those with euthyroid (P = 0.03). Women with TSH< 0.3 mIU/L had a higher odds of preterm delivery than those with TSH≥ 0.3 regardless of urine iodine cut-off [OR= 2.27; 95% CI: (1.15, 4.48), p = 0.02]. Among those with UIC levels≥ 150 μg/L, the odds ratio of preterm delivery was 4.61 folds higher in the SH group compared to those with euthyroid [95%CI: (1.36, 15.71), p = 0.01)]. No significant difference between these two study groups was found in Neonatal Intensive Care Unit admission. Moreover, the results revealed no statistically significant difference in the means of neonatal anthropometric parameters in the SH and euthyroid groups in none of the subgroups of UIC (<150 or ≥150 µg/l).

CONCLUSIONS

According to our results, maternal SH appears to be a risk factor for preterm delivery. This effect is more pronounced in women with higher UIC than those with lower UIC.

Levothyroxine Therapy in Elderly Patients With Hypothyroidism

Levothyroxine (L-T4) treatment of overt hypothyroidism can be more challenging in elderly compared to young patients. The elderly population is growing, and increasing incidence and prevalence of hypothyroidism with age are observed globally. Elderly people have more comorbidities compared to young patients, complicating correct diagnosis and management of hypothyroidism. Most importantly, cardiovascular complications compromise the usual start dosage and upward titration of L-T4 due to higher risk of decompensating cardiac ischemia and -function. It therefore takes more effort and care from the clinician, and the maintenance dose may have to be lower in order to avoid a cardiac incidence. On the other hand, L-T4 has a beneficial effect on cardiac function by increasing performance. The clinical challenge should not prevent treating with L-T4 should the patient develop e.g., cardiac ischemia. The endocrinologist is obliged to collaborate with the cardiologist on prophylactic cardiac measures by invasive cardiac surgery or medical therapy against cardiac ischemic angina. This usually allows subsequent successful treatment. Management of mild (subclinical) hypothyroidism is even more complex. Prevalent comorbidities in the elderly complicate correct diagnosis, since many concomitant morbidities can result in non-thyroidal illness, resembling mild hypothyroidism both clinically and biochemically. The diagnosis is further complicated as methods for measuring thyroid function (thyrotropin and thyroxine) vary immensely according to methodology and background population. It is thus imperative to ensure a correct diagnosis by etiology (e.g., autoimmunity) before deciding to treat. Even then, there is controversy regarding whether or not treatment of such mild forms of hypothyroidism in elderly will improve mortality, morbidity, and quality of life. This should be studied in large cohorts of patients in long-term placebo-controlled trials with clinically relevant outcomes. Other cases of hypothyroidism, e.g., medications, iodine overload or hypothalamus-pituitary-hypothyroidism, each pose specific challenges to management of hypothyroidism; these cases are also more frequent in the elderly. Finally, adherence to treatment is generally challenging. This is also the case in elderly patients, which may necessitate measuring thyroid hormones at individually tailored intervals, which is important to avoid over-treatment with increased risk of cardiac morbidity and mortality, osteoporosis, cognitive dysfunction, and muscle deficiency.

Early detection of biochemically occult autonomous thyroid nodules

OBJECTIVE

Autonomously functioning thyroid areas may be associated with subclinical or overt hyperthyroidism, but may exist even in the presence of normal TSH. This study was aimed at comparing the rate of autonomously functioning areas and their cardiac sequelae in patients with nodular goitre studied with the usual and a novel approach.

DESIGN AND METHODS

In total 490 adult outpatients with thyroid nodular goitre, living in a mild iodine-deficient area, were selected in our referral centre for thyroid diseases from 2009 to 2014 on the basis of a suspicion of thyroid functional autonomy. They were divided in three groups according to a non-conventional approach (excessive response to thyroxine treatment: group 1) or conventional approach (low/normal TSH with clinical suspicion or low TSH: groups 2 and 3). All patients of the study with the suspicion of thyroid functional autonomy underwent thyroid scan with radioactive iodine (I¹³¹) uptake (RAIU).

RESULTS

The percentage of confirmed thyroid functional autonomy was 319/490, being significantly higher in group 3 than in groups 1 and 2 (81.5 vs 64.7 vs 52.6%; chi-square P < 0.0001). However, the diagnosis with non-conventional approach was made at a significant earlier age (P < 0.0001). Cardiac arrhythmias as well as atrial fibrillation were similarly detected by conventional and non-conventional approaches (chi-square test: P = 0.2537; P = 0.8425).

CONCLUSIONS

The hyper-responsiveness to thyroxine treatment should induce the suspicion of thyroid functional autonomy at an early stage, allowing to detect autonomous functioning areas in apparently euthyroid patients.

Subclinical Thyroid Disorders: Clinical Significance and When to Treat?

Subclinical thyroid disorders are commonly encountered in the primary care setting. This article aims to review the latest evidence and guidelines pertaining to the management of subclinical hypo- and hyperthyroidism, in particular the important decision of when treatment should be considered.

The impact of Graves' disease and its treatment on handwriting characteristics

BACKGROUND

Thyroid hormones are crucial for metabolism in all tissues in humans, including the nervous system and muscles, and could thus affect handwriting, which is the synthesis of complex and fine movements. Hyperthyroidism, characterized by symptoms such as tremor and weakness, could affect handwriting, although this has not been studied yet. The aim of this study was to evaluate handwriting characteristics before and after therapy for hyperthyroid Graves' disease (GD).

METHODS

Twenty-two patients (15 women, 7 men) with untreated GD (median age: 44 years; range: 20-70 years) were asked to write a "standard text" before and 12 months after being rendered euthyroid. The letters underwent a standardized detailed analysis by a handwriting expert, through inspection and stereoscopic microscope and magnifying glass.

RESULTS

All patients demonstrated handwriting variations, perceptible even to direct observation. Graphological examination showed statistically significant changes after patients become euthyroid, in the following parameters: size of letters (4.5±1.1 vs. 5.9±1.3 mm; p<0.01), distance between letters (62.9±1.1 vs. 55.2±0.8 mm; p<0.01), width of letters (1.75±0.06 vs. 2.2±0 .06 mm; p<0.01), distance between words (216.2±3.2 vs. 198.7±2.4 mm; p<0.01), extension of letters (8.7±0.2 vs. 7.7±0.2 mm; p<0.01), angles (17±0.3 vs. 15.8±0.4 mm; p<0.01), and groove depth (0.2±0.05 vs. 0.4±0.05 mm; p<0.01).

CONCLUSIONS

Hyperthyroid GD was associated with significant changes in handwriting in all patients. Following recovery from hyperthyroidism, a state of hypertrophic and contracted handwriting resulted in greater fluency and fluidity. Variations in handwriting should be included as signs/symptoms in GD.

Clinical concepts on thyroid emergencies

OBJECTIVE

Thyroid-related emergencies are caused by overt dysfunction of the gland which are so severe that require admission to intensive care units (ICU) frequently. Nonetheless, in the ICU setting, it is crucial to differentiate patients with non-thyroidal illness and alterations in thyroid function tests from those with intrinsic thyroid disease. This review presents and discusses the main etiopathogenetical and clinical aspects of hypothyroid coma (HC) and thyrotoxic storm (TS), including therapeutic strategy flow-charts. Furthermore, a special chapter is dedicated to the approach to massive goiter, which represents a surgical thyroid emergency.

DATA SOURCE

We searched the electronic MEDLINE database on September 2013. Data Selection and Data Extraction: Reviews, original articles, and case reports on "myxedematous coma," "HC," "thyroid storm," "TS," "massive goiter," "huge goiter," "prevalence," "etiology," "diagnosis," "therapy," and "prognosis" were selected.

DATA SYNTHESIS AND CONCLUSION

Severe excess or defect of thyroid hormone is rare conditions, which jeopardize the life of patients in most cases. Both HC and TS are triggered by precipitating factors, which occur in patients with severe hypothyroidism or thyrotoxicosis, respectively. The pillars of HC therapy are high-dose l-thyroxine and/or tri-iodothyroinine; i.v. glucocorticoids; treatment of hydro-electrolyte imbalance (mainly, hyponatraemia); treatment of hypothermia; often, endotracheal intubation and assisted mechanic ventilation are needed. Therapy of TS is based on beta-blockers, thyrostatics, and i.v. glucocorticoids; eventually, high-dose of iodide compounds or lithium carbonate may be of benefit. Surgery represents the gold standard treatment in patients with euthyroid massive nodular goiter, although new techniques - e.g., percutaneous laser ablation - are helpful in subjects at high surgical risk or refusing operation.

Effects of polybrominated diphenyl ethers on thyroid hormone, neurodevelopment and fertility in rodents and humans

Polybrominated diphenyl ethers (PBDEs) are used as flame retardants. Due to their widespread use in many consumer products, PBDEs can be found in food as well as in the environment. Their presence has also been found in the human serum, human adipose tissue and human breast milk. Results of experimental studies suggest that the presence of PBDE in the environment is not neutral to our health. In rats and mice exposed to PBDE disturbances in thyroid hormone homeostasis and reproductive system such as changes in reproductive organs weight and disorders in sperm motility and motion were found. In rodents, pre- and postnatal exposure to PBDE can cause neurobehavioral effects. Also in humans disturbances in thyroid hormone system, weight of reproductive organs and concentrations of sex hormones associated with PBDEs serum concentrations were found. Exposure to PBDEs during pregnancy may lead to slower mental and psychomotor development in infants. In this paper the results of previous animal and human studies are reviewed.

Management of subclinical hyperthyroidism

The ideal approach for adequate management of subclinical hyperthyroidism (low levels of thyroid-stimulating hormone [TSH] and normal thyroid hormone level) is a matter of intense debate among endocrinologists. The prevalence of low serum TSH levels ranges between 0.5% in children and 15% in the elderly population. Mild subclinical hyperthyroidism is more common than severe subclinical hyperthyroidism. Transient suppression of TSH secretion may occur because of several reasons; thus, corroboration of results from different assessments is essential in such cases. During differential diagnosis of hyperthyroidism, pituitary or hypothalamic disease, euthyroid sick syndrome, and drug-mediated suppression of TSH must be ruled out. A low plasma TSH value is also typically seen in the first trimester of gestation. Factitial or iatrogenic TSH inhibition caused by excessive intake of levothyroxine should be excluded by checking the patient's medication history. If these nonthyroidal causes are ruled out during differential diagnosis, either transient or long-term endogenous thyroid hormone excess, usually caused by Graves' disease or nodular goiter, should be considered as the cause of low circulating TSH levels. We recommend the following 6-step process for the assessment and treatment of this common hormonal disorder: 1) confirmation, 2) evaluation of severity, 3) investigation of the cause, 4) assessment of potential complications, 5) evaluation of the necessity of treatment, and 6) if necessary, selection of the most appropriate treatment. In conclusion, management of subclinical hyperthyroidism merits careful monitoring through regular assessment of thyroid function. Treatment is mandatory in older patients (> 65 years) or in presence of comorbidities (such as osteoporosis and atrial fibrillation).

Lifestyle factors, medications, and disease influence bone mineral density in older men: findings from the CHAMP study

Aging alone is not the only factor accounting for poor bone health in older men. There are modifiable factors and lifestyle choices that may influence bone health and result in higher bone density and lower fracture risk even in very old men.

INTRODUCTION

The aim of this cross-sectional analysis was to identify the factors associated with areal bone mineral density (BMD) and their relative contribution in older men.

METHODS

The Concord Health and Ageing in Men Project is a population-based study in Sydney, Australia, involving 1,705 men aged 70-97. Data were collected using questionnaires and clinical assessments. BMD of the hip and spine was measured by dual X-ray absorptiometry.

RESULTS

In multivariate regression models, BMD of the hip was associated with body weight and bone loading physical activities, but not independently with age. The positive relationship between higher BMD and recreational activities is attenuated with age. Factors independently associated with lower BMD at the hip were inability to stand from sitting, a history of kidney stones, thyroxine use, and Asian birth and at the spine, chronic obstructive pulmonary disease, paternal fracture history, and thyroxine use. Higher body weight, participation in dancing, tennis or jogging, quadriceps strength, alcohol consumption, and statin use were associated with higher hip BMD, while older age, osteoarthritis, higher body weight, and aspirin use were associated with higher spinal BMD.

CONCLUSION

Maintaining body weight, physical activity, and strength were positively associated with BMD even in very elderly men. Other parameters were also found to influence BMD, and once these were included in multivariate analysis, age was no longer associated with BMD. This suggests that age-related diseases, lifestyle choices, and medications influence BMD rather than age per se.

An analysis of the natural course of subclinical hyperthyroidism

BACKGROUND

Our aim was to evaluate the incidence rate of overt hyperthyroidism in a cohort of patients with subclinical hyperthyroidism and to assess the potential risk factors for the development of overt thyroid hyperfunction.

METHODS

We performed a retrospective analysis in 75 patients (68 women, mean age 62.2 +/- 14.2 years) with subclinical hyperthyroidism and different grades of serum thyrotropin (TSH) suppression. Incidence rate of overt hyperthyroidism and survival time, ie, time without requiring therapy for overt hyperthyroidism, were studied.

RESULTS

Thirty-four patients (45.3%) developed overt hyperthyroidism and 15 (20.0%) reverted to normal TSH values. The incidence rate of overt hyperthyroidism was 9.69 cases per 100 patient-year in the whole population and 4.12, 7.41, and 29.63 cases per 100 patient-year in subjects with initial TSH values of 0.30 to 0.49, 0.10 to 0.29, and <0.10 mU/L, respectively. Kaplan-Meier analysis of survival time curves showed that the development of overt thyroid hyperfunction was significantly related to the presence of symptoms of hyperthyroidism (P < 0.05) and low (<0.10 mU/L) TSH concentrations (P < 0.001). A stepwise multivariate Cox regression analysis showed that both symptoms and low TSH values were significant factors for progression to overt thyrotoxicosis.

CONCLUSIONS

TSH concentration is the most powerful predictor in the outcome of patients with subclinical hyperthyroidism. Our results suggest that patients with values under 0.10 mU/L have the highest probability to develop overt thyroid hyperfunction. In patients with TSH values higher than this value, the risk of progression is notably lower.

The effect of famotidine, esomeprazole, and ezetimibe on levothyroxine absorption

BACKGROUND

Recent literature describing the effect of gastric acid suppression on levothyroxine absorption has been inconsistent. Also, ezetimibe, a lipid-lowering compound that inhibits intestinal absorption of cholesterol, may interfere with levothyroxine absorption. The objective of this study was to measure changes in levothyroxine absorption before and after famotidine, esomeprazole or single-dose ezetimibe."

METHODS

We conducted levothyroxine absorption testing on 30 healthy volunteers, excluding those with thyroid disease. Subjects were randomized to receive one of three regimens: 1 week of either famotidine or esomeprazole, or a single dose of ezetimibe administered simultaneously with levothyroxine (n = 10 in each group). Baseline levothyroxine absorption testing was performed on all subjects using 600 mcg of Synthroid with thyroid hormone levels checked at 0, 2, 4, 6, and 8 hours after administration, and then repeated 6 weeks later, after administration of one of the three study drug regimens. The area under the curve (AUC) over 8 hours for serum thyroxine (T4), triiodothyronine (T3), and free T4 index, and the mean peak hormone levels achieved during levothyroxine absorption testing at baseline and following administration of one of the three study medications were compared using paired t-tests.

RESULTS

Peak mean hormone levels and AUCs of T4, T3, and free T4 index during absorption testing before and after each of three study medications did not differ. Results for differences before and after study medication did not reach significance even when using the subtractive correction method of AUC calculation.

CONCLUSIONS

No differences were noted in levothyroxine absorption after gastric acid suppression with 1 week of famotidine or esomeprazole. A simultaneously administered dose of ezetimibe did not significantly change levothyroxine absorption.

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.

Early abnormalities of left ventricular myocardial characteristics associated with subclinical hyperthyroidism

The aim of the present study was to analyze heart function in subclinical hyperthyroidism (sHT) in otherwise healthy subjects by new methods using intramyocardial ultrasonic techniques. Twenty-four newly diagnosed and untreated sHT patients (20 women, 4 men; mean age: 42+/-4 yr) and 24 sex- and age-matched healthy volunteers were studied. All subjects were submitted to conventional 2D color-Doppler echocardiography, pulsed wave tissue Doppler imaging (PWTDI) for the analysis of diastolic function, color Doppler myocardial imaging (CDMI) for the analysis of regional strain and strain rate (SR) expression of regional myocardial deformability, and to integrated backscatter (IBS) for the evaluation of intrinsic contractility and tissue characterization. Regional myocardial systolic strain findings were significantly higher in sHT patients when compared with controls (p<0.001). Considering diastolic SR, the early phase of diastolic SR was compromised in sHT subjects as compared with controls (p<0.001). Cyclic variation index (CVI), expression of intrinsic contractility, was significantly higher in sHT subjects in comparison with controls (p<0.0001). IBS values were comparable between the 2 study groups. In conclusion, the present study suggests that in patients with sHT early systolic hyperdeformability and hypercontractility are present, together with impairment of both active and passive phases of diastole. On the contrary, no left ventricular hypertrophy or other structural alterations are documented.

Subclinical hypothyroidism

PURPOSE OF REVIEW

Mild or subclinical hypothyroidism is characterized by normal serum free thyroxine concentrations with elevated serum thyroid-stimulating hormone concentrations. Subclinical hypothyroidism is relatively prevalent in the general population, especially among women and the elderly. The main cause of subclinical hypothyroidism is autoimmune chronic thyroiditis. The present report reviews the most important and recent studies on subclinical hypothyroidism, and discusses the most controversial aspects of this topic.

RECENT FINDINGS

Several studies have demonstrated that subclinical hypothyroidism may affect both diastolic and systolic cardiac function. It may also worsen many risk factors for cardiovascular disease, including hypertension, abnormal endothelial function, and elevated low-density lipoprotein cholesterol concentrations. Furthermore, a growing body of evidence suggests that subclinical hypothyroidism may cause symptoms or progress to symptomatic overt hypothyroidism.

SUMMARY

Prompt treatment of subclinical hypothyroidism in pregnant women is mandatory to decrease risks for pregnancy complications and impaired cognitive development in offspring. Children with subclinical hypothyroidism should be treated to prevent growth retardation. Whether nonpregnant adult patients with subclinical hypothyroidism should be treated, and at what thyroid-stimulating hormone values, is debatable.

Approach to the patient with subclinical hyperthyroidism

Endogenous subclinical hyperthyroidism, defined by normal circulating levels of free T4 and T3 and low levels of TSH, is a common clinical entity and is typically caused by the same conditions that account for the majority of cases of overt hyperthyroidism: Graves' disease, toxic multinodular goiter, and solitary autonomously functioning thyroid nodules. Subclinical hyperthyroidism has been associated with an increased risk of atrial fibrillation and mortality, decreased bone mineral density in postmenopausal women, and mild hyperthyroid symptoms. Treatment of subclinical hyperthyroidism remains controversial, given the lack of prospective randomized controlled trials showing clinical benefit with restoration of the euthyroid state. Nevertheless, it seems reasonable to treat older individuals whose serum TSH levels are less than 0.1 mU/liter and certain high-risk patients, even when the serum TSH is between 0.1 and the lower limit of the normal range.

Exercise performance in young and middle-aged female patients with subclinical hyperthyroidism

Subclinical hyperthyroidism (SH) may be responsible for many cardiovascular changes, including an impaired exercise performance. The aim of our study was to evaluate the response to the treadmill cardiopulmonary test in patients with SH. We studied 14 female patients from our endocrine clinic with exogenous SH, free from cardiovascular diseases, with mean age of 38.6 +/- 10.2 years, body mass index (BMI) of 24.4 +/- 4.0 kg/m(2), and disease duration of 4.9 +/- 4.9 years. The mean serum thyrotropin (TSH) was 0.03 +/- 0.03 mU/L, serum free thyroxine (FT(4)), 1.72 +/- 0.21 ng/dL, and serum triiodothyronine level, 137 +/- 32 ng/dL. The control group comprised 15 euthyroid, healthy women, with mean age of 35.4 +/- 7.4 years and BMI of 27.3 +/- 5.9 kg/m(2). Both groups had a sedentary lifestyle and underwent the cardiopulmonary test using a treadmill with the Balke protocol. Gas concentrations and the respiratory outflow were measured and the electrocardiogram (ECG) was registered in real time. We calculated the minute ventilation (V(E)), the oxygen consumption (peak VO(2)), the carbonic gas exhalation (peak VCO(2)) and the anaerobic threshold (AT). The heart rate (HR) at rest (90.9 +/- 15.7 versus 78.9 +/- 8.7 beats per minute; p = 0.03) was higher in the patients from our clinic. There was no difference between groups regarding age, BMI, fat percentage, blood pressure, peak HR, exercise duration, mean treadmill peak inclination, V(E), peak VO(2), peak VCO(2), and AT. There was no correlation between peak VO(2) and FT(4), TSH, or disease duration. Our results show that exercise capacity in young and middle-aged female patients is not significantly affected by exogenous SH.

Subclinical Hyperthyroidism and Pregnancy Outcomes

OBJECTIVE

Subclinical hyperthyroidism has long-term sequelae that include osteoporosis, cardiovascular morbidity, and progression to overt thyrotoxicosis or thyroid failure. The objective of this study was to evaluate pregnancy outcomes in women with suppressed thyroid-stimulating hormone (TSH) and normal free thyroxine (fT(4)) levels.

METHODS

All women who presented to Parkland Hospital for prenatal care between November 1, 2000, and April 14, 2003, underwent thyroid screening by chemiluminescent TSH assay. Women with TSH values at or below the 2.5th percentile for gestational age and whose serum fT(4) levels were 1.75 ng/dL or less were identified to have subclinical hyperthyroidism. Those women screened and delivered of a singleton infant weighing 500 g or more were analyzed. Pregnancy outcomes in women identified with subclinical hyperthyroidism were compared with those in women whose TSH values were between the 5th and 95th percentiles.

RESULTS

A total of 25,765 women underwent thyroid screening and were delivered of singleton infants. Of these, 433 (1.7%) were considered to have subclinical hyperthyroidism, which occurred more frequently in African-American and/or parous women. Pregnancies in women with subclinical hyperthyroidism were less likely to be complicated by hypertension (adjusted odds ratio 0.66, 95% confidence interval 0.44-0.98). All other pregnancy complications and perinatal morbidity or mortality were not increased in women with subclinical hyperthyroidism.

CONCLUSION

Subclinical hyperthyroidism is not associated with adverse pregnancy outcomes. Our results indicate that identification of subclinical hyperthyroidism and treatment during pregnancy is unwarranted.

LEVEL OF EVIDENCE

II-2.