The clinical significance of subclinical thyroid dysfunction

Effects of physical activity on body composition and fatigue perception in patients on thyrotropin-suppressive therapy for differentiated thyroid carcinoma

BACKGROUND

Subclinical thyrotoxicosis (scTox) may be associated with alterations in body composition and fatigue that can be possibly reversed with physical activity. The aim of the present study was to evaluate whether the systematic practice of physical activity improves lower extremity muscle mass and fatigue perception in patients with scTox.

MATERIALS AND METHODS

We studied 36 patients (2 men) with median age of 48.0 (43.0-51.0) years, body mass index of 27.4 (22.1-30.2) kg/m(2), thyrotropin <0.4 mU/L, and free thyroxine between 0.8 and 1.9 ng/dL and 48 control subjects (C group; 7 men). Patients were randomly divided in two groups according to the adherence to the exercise training: scTox-Tr (n = 19)-patients who adhered to the exercise intervention and scTox-Sed (n = 17)--patients who did not adhere to it. The C group did not participate in the randomization. The exercise training was supervised by a physical education instructor, and it was composed of 60 minutes of aerobic activity and stretching exercises, twice a week, during 12 weeks. In both groups, body composition was assessed (anthropometric method), and the Chalder Fatigue Scale was determined at baseline and after 3 months of intervention (scTox-Tr group) or observation (scTox-Sed group).

RESULTS

At baseline, patients with scTox had lower muscle mass and mid-thigh girth and more fatigue on the Chalder Fatigue Scale than euthyroid control subjects. The scTox-Tr group had an increase in muscle mass, reduction in the variables reflecting whole body fat, and lesser perception of fatigue during the exercise training period (p ≤ 0.05 for these parameters at the start and end of the exercise training period).

CONCLUSIONS

scTox is associated with lower muscle mass and mid-thigh girth and more fatigue. Physical activity training can partially ameliorate these characteristics. More studies are needed to determine what training program would be optimum, both in terms of beneficial effects and for avoiding potential adverse responses.

Thyroid hormone and cardiac disease: from basic concepts to clinical application

Nature's models of regeneration provide substantial evidence that a natural healing process may exist in the heart. Analogies existing between the damaged myocardium and the developing heart strongly indicate that regulatory factors which drive embryonic heart development may also control aspects of heart regeneration. In this context, thyroid hormone (TH) which is critical in heart maturation during development appears to have a reparative role in adult life. Thus, changes in TH -thyroid hormone receptor (TR) homeostasis are shown to govern the return of the damaged myocardium to the fetal phenotype. Accordingly, thyroid hormone treatment preferentially rebuilds the injured myocardium by reactivating developmental gene programming. Clinical data provide further support to this experimental evidence and changes in TH levels and in particular a reduction of biologically active triiodothyronine (T3) in plasma after myocardial infarction or during evolution of heart failure, are strongly correlated with patients morbidity and mortality. The potential of TH to regenerate a diseased heart has now been testing in patients with acute myocardial infarction in a phase II, randomized, double blind, placebo-controlled study (the THiRST study).

[Cognitive dysfunction in patients with subclinical hypothyroidism]

OBJECTIVE

Evaluate neuropsychological changes in patients with subclinical hypothyroidism (SH).

SUBJECTS AND METHODS

Cross-sectional study comparing the results of the neuropsychological evaluation of 89 SH patients and 178 individuals without thyroid disease. The participants underwent the following neuropsychological assessment: Conner's Continuous Performance Test (CPT-II), Iowa Gambling Task, Stroop Test, Wisconsin Card Sorting Test (WCST), Verbal Fluency Test (semantic and phonologic categories) and Rey Auditory Verbal Learning Test.

RESULTS

Among the neuropsychological tests, patients showed worse performance only in cognitive flexibility (WCST) and the ability to maintain sustained attention (omission errors on the CPT-II).

CONCLUSIONS

These losses can cause detriments in the daily lives of patients, constituting potential treatment indications.

Contributions of HIV infection in the hypothalamus and substance abuse/use to HPT dysregulation

Over the last two decades, consequences of HIV infection of the CNS on disease severity and clinical neuropsychiatric manifestations have changed. These changes are due, in part, to improved control of peripheral infection by new anti-retroviral medications and more efficient CNS penetration of combination anti-retroviral therapies (cART). While the life spans of HIV-infected patients have been prolonged with successful cART, the spectrum of cognitive alterations observed in these patients has broadened. Recent studies report that there does not appear to be a single prototypical pattern of neuropsychological impairment associated with HIV, but includes diverse manifestations. Some co-morbidities, such as substance abuse or depression likely play significant roles in the neuropsychiatric profiles of some HIV-infected patients. Newly recognized factors contributing to neurocognitive impairments include aging and unanticipated side effects from cART. Likewise, disturbances in neuroendocrine functioning are emerging as potentially important contributors to HIV-associated neurocognitive alterations. A retrospective review of clinical data from a small cohort of HIV-infected patients admitted to the psychiatric unit of an inner city hospital indicates that thyroid stimulating hormone levels were abnormal in 27% of the patients. Our data from analyses of post-mortem tissues from HIV patients show for the first time HIV infection of the hypothalamus and altered levels of thyroid hormone processing enzymes. Decreased vasopressin and oxytocin immunoreactivity in hypothalamic neurons was also observed. Thus, HIV infection of the CNS may contribute to changes in hypothalamic thyroid hormone signaling, thereby resulting in abnormal hypothalamic-pituitary-thyroid axis feedback and neuropsychiatric dysfunction.

Both exogenous subclinical hyperthyroidism and short-term overt hypothyroidism affect myocardial strain in patients with differentiated thyroid carcinoma

BACKGROUND

The cardiovascular effects of transitions from exogenous subclinical hyperthyroidism to short-term overt hypothyroidism in patients treated for differentiated thyroid carcinoma remain unclear. The present study aims at evaluating the changes in multidirectional myocardial strain using two-dimensional (2D) speckle tracking during this controlled transition from exogenous subclinical hyperthyroidism to overt hypothyroidism.

METHODS

The study included 14 patients with differentiated thyroid carcinoma on thyrotropin suppressive thyroxine substitution who were subsequently withdrawn from thyroxine for 4 weeks. Cardiac function was assessed by 2D speckle tracking echocardiography before and 1 and 4 weeks after withdrawal and compared with values obtained in a control group of 24 individuals.

RESULTS

At baseline, the left ventricular dimensions were significantly higher in patients as compared with controls. Using 2D speckle tracking imaging, the patients had significantly impaired baseline myocardial systolic function in the circumferential (-16.0% ± 2.1% vs. -19.2% ± 3.0%, p = 0.001) and longitudinal (-17.1% ± 2.5% vs. -19.7% ± 3.0%, p = 0.001) directions as compared with controls. Withdrawal of thyroid hormone did not induce significant changes in left ventricular dimensions or systolic function. During the transition from exogenous subclinical hyperthyroidism to overt hypothyroidism, a significant improvement in circumferential and longitudinal systolic shortening was observed and returned to abnormal values when the patients were overt hypothyroid (circumferential strain: from -16.0% ± 2.1% to -18.6% ± 1.9% and -14.7% ± 2.8%, p < 0.005; longitudinal strain: from -17.1% ± 2.5% to -18.8% ± 1.4% and -16.3% ± 1.3%, p < 0.005).

CONCLUSIONS

A U-shaped relationship between a range of thyroid hormone levels (from hyper- to hypothyroid concentrations) and myocardial strains was observed. The clinical consequences of these findings remain to be determined but may point out an increased myocardial vulnerability even in states of moderate subclinical hyperthyroidism and short-term hypothyroidism.

Adequacy of thyroid hormone replacement in a general population

BACKGROUND

Suboptimal thyroid hormone replacement may carry harmful health consequences.

AIMS

Our objectives were to determine the prevalence and factors associated with inadequate replacement in patients receiving treatment with levothyroxine.

DESIGN

Retrospective general practice audit.

METHODS

We identified levothyroxine users through electronic searches of primary care records in all 11 practices within a county borough. The adequacy of thyroid hormone replacement was determined from the current serum, serum thyrotropin (TSH) as: (i) adequate replacement (normal TSH; 0.4-4.0 mU/l); (ii) over replacement (low TSH; <0.4 mU/l); and (iii) under replacement (high TSH; >4.0 mU/l).

RESULTS

Out of a registered patient population of 58 567, we identified 1037 patients who were first included in the hypothyroidism disease register between January 2004 and December 2009 (mean age 62.4 ± 15.9 years; female 85.9%, male 14.1%). Inadequate replacement was seen in 385 patients (37.2%), comprising 205 patients (19.8%) with over replacement and 180 patients (17.4%) with under replacement. Step-wise logistic regression showed that the factors associated with under replacement were male gender [odds ratio (OR) 2.85, confidence interval (CI) 1.86-4.38; P < 0.001 and younger age (OR 0.88, CI 0.80-0.98; P = 0.02 per 10 year increase in age) while longer duration of treatment was associated with over-treatment (OR 1.06, CI 1.01-1.10). A thyroid function test was performed in the preceding 12 months in 914 patients (88.1%) and appropriate dose adjustments had been made in 81.0% (312/385) of patients with abnormal results.

CONCLUSION

Despite frequent monitoring and dose adjustment activities, inadequate thyroid hormone replacement remained a problem in over a third of levothyroxine users in this population.

Prevalence of clinical and subclinical thyroid disease in a peritoneal dialysis population

AIMS

We investigated dialysis duration, dose of erythropoietin (EPO), and clinical manifestations in peritoneal dialysis (PD) patients with subclinical hypothyroidism.

METHODS

This cross-sectional study, performed in 3 centers, assessed 122 adult patients on PD for more than 6 months with regard to demographic data, dialysis duration, thyroid function, biochemical data, EPO dose, and clinical manifestations. Thyroid dysfunction was determined by serum thyroid-stimulating hormone, free thyroxine, total thyroxine, total triiodothyronine, antithyroid peroxidase antibodies, and auto-antibodies against thyroglobulin.

RESULTS

Of the 122 study patients, 98 (80.3%) were assessed as having euthyroidism; 19 (15.6%), subclinical hypothyroidism; and 5 (4.1%), subclinical hyperthyroidism. The proportion of women (74.2% vs. 57.1%, p = 0.038), the mean duration of PD (58.1 months vs. 37.9 months, p = 0.032), and the weighted mean monthly EPO dose (1.22 μg/kg vs. 1.64 μg/kg, p = 0.009) were significantly higher in the subclinical hypothyroidism group than in the euthyroidism group, but the prevalences of coronary artery disease and cerebrovascular disease were not. From the multivariate model, PD duration was more significant than sex as a risk factor for subclinical hypothyroidism (p = 0.0132).

CONCLUSIONS

Subclinical hypothyroidism is frequent in PD patients, especially female patients and patients with a longer PD duration. Compared with euthyroid patients, patients with subclinical hyperthyroidism need a higher dose of EPO to maintain a stable hemoglobin level.

The TSH upper reference limit: where are we at?

The diagnosis of subclinical hypothyroidism--serum TSH levels above and T(4) levels within the laboratory reference ranges--depends critically on the upper limit of the TSH reference interval. Calls have been made to lower the current upper TSH reference limit of 4.0 mU/l to 2.5 mU/l to exclude patients with occult hypothyroidism. However, data from population studies do not indicate that the distribution of TSH is altered owing to inclusion of such individuals. The opposite suggestion has also been put forward; the TSH upper reference limit is often too low, especially in the elderly, in women and in white individuals, which may lead to unnecessary or even harmful therapy. Studies in elderly individuals have shown that although aging may be associated with increased TSH levels, paradoxically, overt hypothyroidism in this population may be associated with a less robust TSH response than in young individuals. This Review highlights the interindividual and intraindividual variability of TSH levels and discusses the current controversy that surrounds the appropriateness of reference ranges defined on the basis of age, race, sex and amount of iodine intake. Moreover, the current evidence on lowering or increasing the upper limit of the TSH reference interval is reviewed and the need to individualize levothyroxine treatment in patients with elevated TSH levels is discussed.

Low-normal or high-normal thyrotropin target levels during treatment of hypothyroidism: a prospective, comparative study

BACKGROUND

Recent literature advocates the decrease of the upper limit of the normal thyrotropin (TSH) reference range. The objective of this study was to determine whether treated hypothyroid patients maintained within a low-normal TSH range (0.4-2.0 mIU/L) have better clinical outcomes than those maintained within a high-normal TSH range (2.0-4.0 mIU/L).

METHODS

The study was performed in a thyroid outpatient clinic of a tertiary hospital. This was a prospective, interventional study. Forty-two participants with newly diagnosed overt primary hypothyroidism were paired in two groups: group 1 (n=20), low-normal target TSH; group 2 (n = 22), high-normal target TSH. Levothyroxine was initiated, and dose was adjusted to achieve and sustain the target TSH value during the study period. After the target TSH was reached, participants were evaluated every 3 months for thyroid function, serum lipid profile, resting energy expenditure (REE), body composition, and bone mineral density, for 12 months.

RESULTS

Nineteen patients in group 1 and 16 in group 2 completed the study. In the whole-group analysis, total cholesterol (p = 0.01), low-density lipoprotein cholesterol (p = 0.004), and triglycerides (p < 0.001) decreased after treatment, whereas REE per kilogram of lean body mass (p = 0.001) and total fat body mass (p =0.02) increased. Group 1 patients had a significantly higher relative increase in REE (+7.1% ± 11.3% vs. +3.6% ± 15.1%, p = 0.02). There was no difference between the groups in the other variables.

CONCLUSIONS

Despite recent trends toward lowering the upper limit of normal TSH range, the results of this 12-month study provided no substantial clinical evidence to corroborate that treatment of primary hypothyroidism should aim at maintaining TSH levels in a low-normal range

Hypothyroidism and hypertension

Hypothyroidism has been recognized as a cause of secondary hypertension. Previous studies on the prevalence of hypertension in subjects with hypothyroidism have demonstrated elevated blood pressure values. Increased peripheral vascular resistance and low cardiac output has been suggested to be the possible link between hypothyroidism and diastolic hypertension. The hypothyroid population is characterized by significant volume changes, initiating a volume-dependent, low plasma renin activity mechanism of blood pressure elevation. This article summarizes previous studies on the impact of hypothyroidism on blood pressure and early atherosclerotic process.

Update: Systemic Diseases and the Cardiovascular System (II). The endocrine system and the heart: a review

Normal endocrine function is essential for cardiovascular health. Disorders of the endocrine system, consisting of hormone hyperfunction and hypofunction, have multiple effects on the cardiovascular system. In this review, we discuss the epidemiology, diagnosis, and management of disorders of the pituitary, thyroid, parathyroid, and adrenal glands, with respect to the impact of endocrine dysfunction on the cardiovascular system. We also review the cardiovascular benefits of restoring normal endocrine function.

Effects of thyroid dysfunction on lipid profile

Thyroid dysfunction has a great impact on lipids as well as a number of other cardiovascular risk factors. Hypothyroidism is relatively common and is associated with an unfavorable effect on lipids. Substitution therapy is beneficial for patients with overt hypothyroidism, improving lipid profile. However, whether subclinical hypothyroidism should be treated or not is a matter of debate. On the other hand, hyperthyroidism can be associated with acquired hypocholesterolemia or unexplained improvement of lipid profile. Overall, thyroid dysfunction should be taken into account when evaluating and treating dyslipidemic patients.

[Autoimmune thyroiditis (Hashimoto's thyroiditis): current diagnostics and therapy]

Hashimoto's thyroiditis is a common autoimmune thyroid disease with preference of female gender. The chronic thyroiditis is characterized by autoantibodies against thyroid peroxidase and thyroglobulin. With manifestation, there is often a subclinical hypothyroidism that finally progresses to a persistent hypothyroidism with typical clinical symptoms and the need of hormonal substitution in succession of the lymphocytic infiltration of the thyroid. The ultrasound of the thyroid shows a hypoechogenic and inhomogeneous parenchyma. Autoimmune thyroiditis is frequently associated with autoimmune disease of other organs, such as vitiligo, Addison's disease, diabetes mellitus type 1, often in the sense of polyglandular syndrome 2.

Update: Systemic Diseases and the Cardiovascular System (II). The endocrine system and the heart: a review

Normal endocrine function is essential for cardiovascular health. Disorders of the endocrine system, consisting of hormone hyperfunction and hypofunction, have multiple effects on the cardiovascular system. In this review, we discuss the epidemiology, diagnosis, and management of disorders of the pituitary, thyroid, parathyroid, and adrenal glands, with respect to the impact of endocrine dysfunction on the cardiovascular system. We also review the cardiovascular benefits of restoring normal endocrine function.

Subclinical thyrotoxicosis in an outpatient population - predictors of outcome

OBJECTIVE

Individuals with endogenous subclinical thyrotoxicosis (SCT) may subsequently require treatment for overt disease. We aimed to evaluate the frequency of progression to hyperthyroidism and factors influencing this outcome.

DESIGN

This is a retrospective analysis of outcome in 96 consecutive patients (aged 16-91 years) diagnosed with SCT over a 6-year period. Individuals with secondary causes of TSH suppression were excluded. Mean follow-up was 3·8 years. The significance of age, gender, family history of thyrotoxicosis, symptoms at presentation, thyroid nodule(s) on clinical examination, entry TSH level, antithyroid antibody status and (99m) Tc pertechnetate thyroid imaging results on subsequent development of overt thyrotoxicosis was assessed.

RESULTS

Progression to overt thyrotoxicosis was seen in 8% at 1 year, 16% at 2 years, 21% at 3 years and 26% at 5 years. Multivariate analysis determined that diagnosis as determined by scintiscan to be the only independent predictor of outcome (P = 0·003) with the cumulative percentage requiring therapy at 5 years being 9% for subclinical Graves' disease, 21% for multinodular goitre and 61% for the autonomous nodule subgroup.

CONCLUSIONS

Progression of SCT to overt hyperthyroidism occurred at a rate of 5-8% per year with disease aetiology, as determined by thyroid scintigraphy, significantly influencing risk of progression.

[Potential risks of the adverse effects of thyrotropin suppression in differentiated thyroid carcinoma]

In patients with differentiated thyroid carcinoma, long-term inhibition of thyrotropin (TSH) secretion through levothyroxine administration is required when there is evidence of persistent or recurrent disease. In these cases, levothyroxine doses should be monitored to achieve the objectives of inhibiting TSH and avoiding clinical hyperthyroidism. The possibility that suppressive therapy may produce deleterious effects is still controversial, mainly in elderly patients. There are many studies on the potential harmful effects of suppressive therapy on various organs and systems with discrepant results. However, there is no scientific evidence that the clinical impact of these effects is significant.

Myxedema coma in a patient with subclinical hypothyroidism

BACKGROUND

Myxedema coma is the extreme manifestation of hypothyroidism, typically seen in patients with severe biochemical hypothyroidism. Its occurrence in association with subclinical hypothyroidism is extremely unusual. We describe a patient with subclinical hypothyroidism who developed clinical manifestations of myxedema coma.

SUMMARY

A 47-year-old woman presented to our endocrine clinic with complaints of fatigue and biochemical findings of subclinical hypothyroidism. She was started on treatment with thyroxine (T4) but remained unwell and was later admitted to hospital with hormone profile showing persisting subclinical hypothyroidism (elevated thyrotropin and normal free T4 [FT4] and free triiodothyronine [FT3]): FT4 10.7 pmol/L (reference range 10.3-24.5), FT3 2.7 pmol/L (reference range 2.67-7.03), and thyrotropin 6.09 mU/L (reference range 0.4-4.0). She subsequently developed hypothermia (temperature 33.2°C), circulatory collapse, and coma. Biochemical profile showed hyponatremia, elevated creatinine phosphokinase, metabolic acidosis, and renal failure. An echocardiogram revealed a moderate-sized pericardial effusion. We diagnosed myxedema coma and started treatment with intravenous T3. She responded dramatically with improvement in level of consciousness and normalization of metabolic parameters. We found no explanation other than hypothyroidism to account for the presentation. Adrenocorticotrophic hormone (ACTH) stimulation tests excluded adrenal insufficiency, and serum gonadotrophins were within the normal reference range. FT4 estimation by equilibrium dialysis excluded analytical interference, and molecular analysis for the thyroid hormone receptor β gene associated with thyroid hormone resistance was negative.

CONCLUSIONS

To the best of our knowledge this is the first report of myxedema coma in a patient with subclinical hypothyroidism. The reason for normal thyroid hormone levels is unclear but may reflect deviation from a higher pre-morbid set-point. The case highlights the importance of careful clinical evaluation in patients with disparate clinical and laboratory findings.

Effects of thyroxine replacement on endothelial function and carotid artery intima-media thickness in female patients with mild subclinical hypothyroidism

BACKGROUND

Previous studies have suggested an association between subclinical hypothyroidism and coronary artery disease that could be related to changes in serum lipids or endothelial dysfunction.

METHODS

Thirty-two female subclinical hypothyroidism patients were randomly assigned to 12 months of L-thyroxine replacement or no treatment. Endothelial function was measured by the flow-mediated vasodilatation of the brachial artery, as well as mean carotid artery intima-media thickness, and lipid profiles were studied at baseline and after 12 months of follow-up.

RESULTS

The mean ( ± SD) serum thyroid-stimulating hormone levels in the L-thyroxine replacement and control groups were 6.09 ± 1.32 and 6.27 ± 1.39 μUI/ml, respectively. No relationship between carotid artery intima-media thickness or brachial flow-mediated vasodilatation and free T4 and serum thyroid-stimulating hormone was found. The median L-T4 dose was 44.23 ± 18.13 μg/day. After 12 months, there was a significant decrease in the flow-mediated vasodilatation in the subclinical hypothyroidism control group (before: 17.33 ± 7.88 to after: 13.1 ± 4.75%, p =0.03), but there were no significant differences in flow-mediated vasodilatation in the L-thyroxine treated group (before: 16.81 ± 7.0 to after: 18.52 ± 7.44%, p = 0.39). We did not find any significant change in mean carotid intimamedia thickness after 12 months of L-thyroxine treatment.

CONCLUSION

Replacement therapy prevents a decline in flow-mediated vasodilatation with continuation of the subclinical hypothyroidism state. Large prospective multicenter placebo-controlled trials are necessary to investigate endothelial physiology further in subclinical hypothyroidism patients and to define the role of L-thyroxine therapy in improving endothelial function in these patients.

Thyroid hormone therapy modulates hypothalamo-pituitary-adrenal axis

To observe the influence of thyroid hormone therapy on hypothalamo-pituitary-adrenal (HPA) axis, a group of 14 athyreotic women due to thyroid cancer treatment were studied before and after thyroid suppression therapy with thyroxine (T4). Changes in plasma adrenocorticotropin (ACTH) and cortisol levels in response to human corticotropin-releasing hormone (hCRH; 100µg, i.v.) were estimated under hypothyroid conditions and after T4 suppression therapy with 2.5µg/kg/day for two months (n=14). A group of seven healthy women was evaluated as a control group. A greater increase in ACTH levels by hCRH was observed in patient group both before and after suppression therapy compared than that of control group. Plasma cortisol levels after hCRH stimulation were also greater in patient group both before and after suppression therapy than that of control group. In conclusion, both hypothyroidism and subclinical hyperthyroidism with suppressive doses of thyroid hormone induced a hypersensitivity of ACTH to hCRH. Considering the role of thyroid hormone on HPA axis, the mechanisms of ACTH hypersensitivity may be different between these two conditions.

The epidemiology of thyroid disease

INTRODUCTION

Thyroid disorders are prevalent and their manifestations are determined by the dietary iodine availability.

SOURCES OF DATA

Data from screening large population samples from USA and Europe.

AREAS OF AGREEMENT

The most common cause of thyroid disorders worldwide is iodine deficiency, leading to goitre formation and hypothyroidism. In iodine-replete areas, most persons with thyroid disorders have autoimmune disease.

AREAS OF CONTROVERSY

Definition of thyroid disorders, selection criteria used, influence of age and sex, environmental factors and the different techniques used for assessment of thyroid function.

GROWING POINTS

Increasing incidence of well-differentiated thyroid cancer. Environmental iodine influences the epidemiology of non-malignant thyroid disease.

AREAS TIMELY FOR DEVELOPING RESEARCH

Iodine supplementation of populations with mild-to-moderate iodine deficiency. An evidence-based strategy for the risk stratification, treatment and follow-up of benign nodular thyroid disease. Is there any benefit in screening adults for thyroid dysfunction?

A sexual shift induced by silencing of a single insulin-like gene in crayfish: ovarian upregulation and testicular degeneration

In sequential hermaphrodites, intersexuality occurs naturally, usually as a transition state during sexual re-differentiation processes. In crustaceans, male sexual differentiation is controlled by the male-specific androgenic gland (AG). An AG-specific insulin-like gene, previously identified in the red-claw crayfish Cherax quadricarinatus (designated Cq-IAG), was found in this study to be the prominent transcript in an AG cDNA subtractive library. In C. quadricarinatus, sexual plasticity is exhibited by intersex individuals in the form of an active male reproductive system and male secondary sex characters, along with a constantly arrested ovary. This intersexuality was exploited to follow changes caused by single gene silencing, accomplished via dsRNA injection. Cq-IAG silencing induced dramatic sex-related alterations, including male feature feminization, a reduction in sperm production, extensive testicular degeneration, expression of the vitellogenin gene, and accumulation of yolk proteins in the developing oocytes. Upon silencing of the gene, AG cells hypertrophied, possibly to compensate for low hormone levels, as reflected in the poor production of the insulin-like hormone (and revealed by immunohistochemistry). These results demonstrate both the functionality of Cq-IAG as an androgenic hormone-encoding gene and the dependence of male gonad viability on the Cq-IAG product. This study is the first to provide evidence that silencing an insulin-like gene in intersex C. quadricarinatus feminizes male-related phenotypes. These findings, moreover, contribute to the understanding of the regulation of sexual shifts, whether naturally occurring in sequential hermaphrodites or abnormally induced by endocrine disruptors found in the environment, and offer insight into an unusual gender-related link to the evolution of insulins.

Subclinical hypothyroidism and related biochemical entities in pregnancy: implications and management

Subclinical hypothyroidism (SCH), thyroid autoimmunity and isolated maternal hypothyroxinaemia are diagnoses made on laboratory findings. The two former conditions are commonly identified in the general population, while the term isolated maternal hypothyroxinaemia was developed to highlight potential neurodevelopmental risks in progeny. Each entity has been associated with either obstetric, perinatal and/or child developmental harm in observational studies, although few interventional trials have been performed to guide diagnostic and therapeutic approaches. Once diagnosed, treatment of SCH is recommended by endocrine groups to limit potential risk, given that harm from appropriate therapy is unlikely. Screening for thyroid disorders in pregnancy has traditionally been controversial. Definitive trials are expected to report over coming years and updated consensus guidelines will hopefully resolve this issue.

Thyroid stimulating hormone, cognitive impairment and depression in an older korean population

OBJECTIVE

Associations of thyroid dysfunction with cognitive impairment and depression in late-life have been described but remain controversial. This study aimed to investigate the associations of serum thyroid stimulating hormone (TSH) levels with cognitive impairment and depression after controlling for potential confounding factors.

METHODS

The sample consisted of 495 community residents aged 65 or over in whom serum TSH had been assayed. Cognitive impairment was defined using the Community Screening Interview for Dementia, and depression was diagnosed using the Geriatric Mental State schedule. Age, gender, education, smoking history, physical activity, blood pressure, diabetes, and serum total cholesterol and albumin were included as covariates.

RESULTS

There was a significant association between lower (hyperthyroid) serum TSH levels (<0.5 mIU/L) and cognitive impairment after adjustment [odds ratio 7.12 (95% confidence interval 1.35-37.5)]. However, no association was found between TSH levels and depression.

CONCLUSION

Based on TSH levels, hyperthyroidism but not hypothyroidism was associated with cognitive impairment in this sample, and we found no evidence for an association of either with depression.

Undiagnosed thyroid dysfunction, thyroid antibodies, and iodine excretion in a Mediterranean population

The prevalence of thyroid dysfunction varies in different populations. The aim of this cross-sectional study was to analyze the prevalence of undiagnosed thyroid dysfunction and thyroid antibodies and their relationship with urine iodine excretion in a representative sample of 1,124 (55.5% women; mean age: 44.8 ± 15.2 years) non-hospitalized Mediterranean adults, in Catalonia (Spain). Free thyroxine, thyroid-stimulating hormone, thyroperoxidase and thyroglobulin antibodies, and urine iodine were measured. Undiagnosed thyroid dysfunction was 5.3% (hypothyroidism 3.8%; 56.66% of these subjects were women). The total (diagnosed + undiagnosed) thyroid dysfunction was 8.9% (71.15% women). Thyroperoxidase antibodies were positive in 2.4% of men and 9.4% of women and thyroglobulin antibodies, in 1.3% of men and 3.8% of women. No differences were observed in urine iodine between groups with thyroid dysfunction and euthyroidism, or between subjects with positive or negative antibodies. In subjects over 60, undiagnosed thyroid dysfunction was 9.8% (hypothyroidism 6.9%, hyperthyroidism 3.3%; 36.36% women) and total thyroid dysfunction 13.61% (53.12% women). Women and men over 60 had similar thyroid dysfunction prevalence. Thus, aggressive case-finding should be recommended in both, over 60.

[Thyroid diseases and hypertension]

Thyroid hormones have several well-recognized effects on the vasculature and heart, resulting in characteristic cardiovascular changes in thyroid disease, including an increase in blood pressure. In hyperthyroidism reduced systemic vascular resistance and increased blood volume lead to an enhanced preload, which, in association with reduced afterload, improved contractility, as well as increased beta-adrenergic activity, results in isolated systolic hypertension based on enhanced stroke volume and cardiac output. In contrast, hypothyroidism causes increased systemic vascular resistance in association with decreased arterial compliance resulting in elevated diastolic blood pressure. Therefore in the evaluation of arterial hypertension secondary hypertension based on thyroid disease should always be considered, especially given the fact that blood pressure changes in the course of thyroid dysfunction are usually reversible upon adequate treatment of hypo- or hyperthyroidism.

Subclinical thyroid dysfunction and incident hip fracture in older adults

BACKGROUND

Subclinical thyroid dysfunction is common in older adults and affects bone metabolism, but its effects on fracture risk have not been reported. We sought to determine prospectively whether older men and women with subclinical hyperthyroidism or hypothyroidism have an increased risk of hip fracture.

METHODS

Prospective cohort of 3567 US community-dwelling adults, 65 years or older, with biochemically defined subclinical thyroid dysfunction or euthyroidism was enrolled from June 10, 1989, through May 30, 1990, and followed up through 2004. Main outcome measures included incidence and hazard ratios (HRs), with 95% confidence intervals (CIs), of confirmed incident hip fractures for groups with subclinical hypothyroidism, subclinical hyperthyroidism, and euthyroidism as defined at baseline.

RESULTS

During 39 952 person-years (median follow-up, 13 years), hip fracture incidence (per 1000 men-years) was 13.65 in men with subclinical hyperthyroidism (n = 29) and 10.27 in men with subclinical hypothyroidism (n = 184), both greater than 5.0 in men with euthyroidism (n = 1159). Men with subclinical hypothyroidism had a multivariable-adjusted HR of 2.31 (95% CI, 1.25-4.27); those with subclinical hyperthyroidism, 3.27 (0.99-11.30). After excluding those with baseline use of thyroid-altering medications, men with endogenous subclinical hyperthyroidism had a higher HR of 4.91 (95% CI, 1.13-21.27), as did men with endogenous subclinical hypothyroidism (2.45, 1.27-4.73). Hip fracture incidence (per 1000 women-years) was 8.93 in women with subclinical hypothyroidism (n = 359) and 10.90 in women with subclinical hyperthyroidism (n = 142) compared with 10.18 in women with euthyroidism (n = 1694). No clear association between subclinical dysfunction and fracture was observed in women.

CONCLUSIONS

Older men with subclinical hyperthyroidism or hypothyroidism are at increased risk for hip fracture. Whether treatment of the subclinical syndrome reduces this risk is unknown.

A cross-section analysis of FT3 age-related changes in a group of old and oldest-old subjects, including centenarians' relatives, shows that a down-regulated thyroid function has a familial component and is related to longevity

Background: several studies suggest that a decreased thyroid activity might be favourable in oldest-old subjects and that subclinical thyroid hyperfunction may be detrimental.

Objectives: to verify whether declining levels of circulating thyroid hormones may contribute to longevity.

Design: cross-sectional observational study.

Setting: all subjects were born in Calabria (southern Italy) and their ancestry in the region was ascertained up to the grandparents.

Subjects: six hundred and four home-dwelling subjects (301 females, 303 males), divided into three groups: 278 individuals 60–85 years old; 179 children or nieces/nephews of centenarians who are 60–85 years old; 147 individuals older than 85 years.

Methods: thyroid function parameters were measured in the frame of a comprehensive geriatric assessment.

Results: FT3 and FT4 levels were negatively associated with age. Lower levels of FT3, FT4 and TSH were found in centenarians’ children and nieces/nephews with respect to age-matched controls. Indeed, being a relative of centenarians qualified as an independent correlate of thyroid parameters.

Conclusions: age-related subtle thyroid hypofunction (either due to a familial component or due to a reset of the thyroid function occurring between the sixth and the eighth decade of life) appears to be related to longevity.

Reference range thyroid-stimulating hormone is associated with physical activity energy expenditure in overweight and obese postmenopausal women: a Montreal-Ottawa New Emerging Team Study

Clinical and, to a lesser extent, subclinical hypothyroidism is associated with a variety of metabolic abnormalities, including increased body mass index, unfavorable lipoprotein profile, and increased biomarkers for atherosclerosis. Energy expenditure could act as a confounding factor in the association reported between thyroid-stimulating hormone (TSH) levels and cardiometabolic risk factors. The objective of the study was to investigate the relationship between reference range plasma TSH and energy expenditure as well as blood pressure, lipid, and inflammation parameters in women. One hundred four postmenopausal, overweight and obese, spontaneously euthyroid women were included in the study. We evaluated total energy expenditure by doubly labeled water, resting energy expenditure by indirect calorimetry, physical activity energy expenditure (PAEE = [total energy expenditure × 0.90] - resting metabolic rate), body weight, and percentage of fat mass by dual-energy x-ray absorptiometry. Blood pressure, plasma lipoproteins profile, and high-sensitivity C-reactive protein levels were also measured. Mean TSH was 2.39 ± 1.09 mIU/L. We observed that high-density lipoprotein cholesterol (r = -0.20, P ≤ .05) was negatively associated with TSH, whereas systolic blood pressure (r = 0.21, P ≤ .05) and apolipoprotein B (r = 0.22, P ≤ .05) were positively correlated with TSH. However, these correlations were no longer significant after controlling for PAEE. A significant negative correlation was found between TSH and PAEE (r = -0.23, P ≤ .05). Our results suggest that, although TSH in the reference range is associated with some cardiometabolic risk factors, this is in large part explained by lower PAEE. In turn, lower PAEE could increase the cardiometabolic risk.

Drug-induced osteoporosis: mechanisms and clinical implications

Drug-induced osteoporosis is common and has a significant impact on the prognosis of patients suffering from chronic debilitating diseases. Glucocorticoids are the drugs causing osteoporotic fractures most frequently, but osteoporosis with fractures is observed also in women treated with aromatase inhibitors for breast cancer, in men receiving anti-androgen therapy for prostate cancer, in postmenopausal women treated with high doses of thyroxine, and in men and women treated with thiazolinediones for type 2 diabetes mellitus. Bone loss with fractures also occurs in patients treated with drugs targeting the immune system, such as calcineurin inhibitors, antiretroviral drugs, selective inhibitors of serotonin reuptake, anticonvulsants, loop diuretics, heparin, oral anticoagulants, and proton pump inhibitors.

TSH reference values for adult Brazilian population

OBJECTIVE: To establish limits of normal serum TSH for the adult (18 to 60 years) Brazilian population according to recommendations of the National Academy of Clinical Biochemistry. SUBJECTS AND METHODS: Healthy volunteers were evaluated and those fulfilling the following clinical criteria were selected: absence of known thyroid disease; no use of any interfering medications; no history of head and neck external radiotherapy, type 1 diabetes or autoimmune disease; no family history of thyroid disease, and absence of goiter or palpable nodules. Subjects with anti-thyroperoxidase antibodies and/or altered free T4 were excluded. The sample consisted of 960 subjects (480 males and 480 females). RESULTS: TSH values corresponding to the 2.5th and 97.5th percentiles of the sample were 0.43 and 3.24 mIU/L, respectively. TSH values > 2.5 mIU/L were observed in 9.15% of the volunteers and levels > 3 mIU/L in 3.11%. CONCLUSION: The present study suggests an upper limit of normal TSH of approximately 3.5 mIU/L.

Subclinical hypothyroidism and the risk of coronary heart disease and mortality

CONTEXT

Data regarding the association between subclinical hypothyroidism and cardiovascular disease outcomes are conflicting among large prospective cohort studies. This might reflect differences in participants' age, sex, thyroid-stimulating hormone (TSH) levels, or preexisting cardiovascular disease.

OBJECTIVE

To assess the risks of coronary heart disease (CHD) and total mortality for adults with subclinical hypothyroidism.

DATA SOURCES AND STUDY SELECTION

The databases of MEDLINE and EMBASE (1950 to May 31, 2010) were searched without language restrictions for prospective cohort studies with baseline thyroid function and subsequent CHD events, CHD mortality, and total mortality. The reference lists of retrieved articles also were searched.

DATA EXTRACTION

Individual data on 55,287 participants with 542,494 person-years of follow-up between 1972 and 2007 were supplied from 11 prospective cohorts in the United States, Europe, Australia, Brazil, and Japan. The risk of CHD events was examined in 25,977 participants from 7 cohorts with available data. Euthyroidism was defined as a TSH level of 0.50 to 4.49 mIU/L. Subclinical hypothyroidism was defined as a TSH level of 4.5 to 19.9 mIU/L with normal thyroxine concentrations.

RESULTS

Among 55,287 adults, 3450 had subclinical hypothyroidism (6.2%) and 51,837 had euthyroidism. During follow-up, 9664 participants died (2168 of CHD), and 4470 participants had CHD events (among 7 studies). The risk of CHD events and CHD mortality increased with higher TSH concentrations. In age- and sex-adjusted analyses, the hazard ratio (HR) for CHD events was 1.00 (95% confidence interval [CI], 0.86-1.18) for a TSH level of 4.5 to 6.9 mIU/L (20.3 vs 20.3/1000 person-years for participants with euthyroidism), 1.17 (95% CI, 0.96-1.43) for a TSH level of 7.0 to 9.9 mIU/L (23.8/1000 person-years), and 1.89 (95% CI, 1.28-2.80) for a TSH level of 10 to 19.9 mIU/L (n = 70 events/235; 38.4/1000 person-years; P <.001 for trend). The corresponding HRs for CHD mortality were 1.09 (95% CI, 0.91-1.30; 5.3 vs 4.9/1000 person-years for participants with euthyroidism), 1.42 (95% CI, 1.03-1.95; 6.9/1000 person-years), and 1.58 (95% CI, 1.10-2.27, n = 28 deaths/333; 7.7/1000 person-years; P = .005 for trend). Total mortality was not increased among participants with subclinical hypothyroidism. Results were similar after further adjustment for traditional cardiovascular risk factors. Risks did not significantly differ by age, sex, or preexisting cardiovascular disease.

CONCLUSIONS

Subclinical hypothyroidism is associated with an increased risk of CHD events and CHD mortality in those with higher TSH levels, particularly in those with a TSH concentration of 10 mIU/L or greater.

A review on post-puberty hypothyroidism: a glance at myxedema

Hypothyroidism, is a thyroid disorder accompanied by serum thyroid hormone reduction when thyroxin T4, the main thyroid hormone, reduced, it is followed by disruption of a negative-feed back auto regulatory mechanism on pituitary gland and subsequent thyroid stimulating hormone (TSH) which is released into the blood circulation to stimulate the thyroid gland to produce enough thyroid hormone to compensate for the body hormone requirements. Therefore, reduced serum thyroxin(T4) in principle, triidothyronine (T3) and elevated TSH are laboratory indices for the diagnosis of hypothyroidism. At early stage of hypothyroidism although laboratory measurements of thyroid function test are manifest the thyroid disorder but the patient clinical signs and symptoms may remain unnoticed. If the patient undiagnosed and untreated the condition of hypothyroidism worsen and the clinical manifestation begin to show itself and myxedema is a definition given to the whole picture of untreated hypothyroidism at very end stage the patients enter into myxedema comma with eventual death due to the sever symptoms of hypothyroidism. Among important causative factors leading to catastrophic events in myxedema is life threatening hypothermia, heart and cerebral dysfunctions.

Color-flow doppler sonography in patients with subclinical thyroid dysfunction

OBJECTIVE

To assess the value of color-flow Doppler sonography (CFDS) in evaluating intrathyroidal blood flow and velocity in patients with subclinical thyroid dysfunction.

METHODS

In this prospective study, patients with subclinical hypothyroidism, patients with subclinical hyperthyroidism, and euthyroid patients without known thyroid autoimmune disease who served as controls were included. Subclinical thyroid dysfunction was defined as normal se-rum free thyroxine (FT4) and free triiodothyronine (FT3) in the presence of high (subclinical hypothyroidism), or low-suppressed (subclinical hyperthyroidism) serum thyrotropin (TSH) levels. Serum FT4, FT3, TSH, and antibodies to thyroid peroxidase and thyroglobulin were measured in all participants. In addition, TSH receptor antibody levels were determined in patients with subclinical hyperthyroid-ism. All participants underwent conventional sonography and CFDS. Mean peak systolic velocity (PSV) and resistive index were obtained from multiple extranodular thyroid parenchyma samplings and inferior thyroid artery measurements.

RESULTS

The study population included 27 patients with subclinical hypothyroidism, 15 patients with subclinical hyperthyroidism, and 20 euthyroid patients. Patients with subclinical hypothyroidism had significantly higher mean intrathyroidal PSV values than control patients (19.9 +/- 5.6 cm/s vs 15.7 +/- 4.4 cm/s; P = .008), whereas patients with subclinical hyperthyroidism had significantly higher mean PSV values than control patients at the inferior thyroid artery level (29.7 +/- 10.7 cm/s vs 21.9 +/- 6.8 cm/s; P = .014). Compared with control patients, a greater proportion of patients with subclinical hypothyroidism and patients with subclinical hyperthyroidism had marked CFDS patterns (78% vs 15% [P<.001] and 53% vs 15%; [P<.001], respectively). A significant association was found between positivity for thyroid autoantibodies and intense CFDS patterns. No correlation was found between TSH or thyroid hormone levels and CFDS pattern or blood flow velocity.

CONCLUSION

We have demonstrated that significantly increased thyroid blood flow velocity and vascularity are already present in patients with mild thyroid dysfunction.

Subclinical hypothyroidism and the risk for cardiovascular diseases. Are epidemiological studies giving the right answers?

Vita tárgyát képezi, vajon a szubklinikus hypothyreosis káros hatást fejt-e ki a cardiovascularis rendszerre, amelynek a következménye megnövekedett morbiditás és mortalitás. Ennek a tisztázására számos epidemiológiai vizsgálatot végeztek, mégis ez idáig ezek nem adtak egyértelmű választ. A vizsgálatok kiértékelését számos zavaró körülmény befolyásolja, márpedig ezeket tekintetbe kell venni. A szerzők a TSH-vizsgálat végzésekor életkor-specifikus referenciatartomány meghatározását ajánlják, mivel az életkor előrehaladtával a TSH-szint magasabb érték felé tolódik el. Így elkerülhető lenne kissé emelkedett TSH-szintű idősebb betegek helytelen besorolása a szubklinikus hypothyreosisos csoportba. Újabb vizsgálatok arra utalnak, hogy szubklinikus hypothyreosisban a cardiovascularis betegség kockázata elsősorban a 65 életévnél fiatalabbakon növekszik meg. Ezt a lehetőséget is tekintetbe véve, a jövőben jól tervezett, prospektív, randomizált vizsgálatok elvégzése szükséges, amelyekben tekintetbe veszik a betegek életkorát, a vascularis eseményeket pedig elsődleges végpontnak tekintik. Remélhetőleg ezek megadják majd a választ arra a kérdésre is, vajon a tiroxinnal végzett korai szubsztitúciós kezelés megakadályozhatja-e ezen betegekben az ischaemiás szívbetegség kifejlődését. Orv. Hetil., 2010, 37, 1488–1494.

T3 affects expression of collagen I and collagen cross-linking in bone cell cultures

Thyroid hormones (T3, T4) have a broad range of effects on bone, however, its role in determining the quality of bone matrix is poorly understood. In-vitro, the immortalized mouse osteoblast-like cell line MC3T3-E1 forms a tissue like structure, consisting of several cell layers, whose formation is affected by T3 significantly. In this culture system, we investigated the effects of T3 on cell multiplication, collagen synthesis, expression of genes related to the collagen cross-linking process and on the formation of cross-links.

T3 compared to controls modulated cell multiplication, up-regulated collagen synthesis time and dose dependently, and stimulated protein synthesis. T3 increased mRNA expressions of procollagen-lysine-1,2-oxoglutarate 5-dioxygenase 2 (Plod2) and of lysyloxidase (Lox), both genes involved in post-translational modification of collagen. Moreover, it stimulated mRNA expression of bone morphogenetic protein 1 (Bmp1), the processing enzyme of the lysyloxidase-precursor and of procollagen. An increase in the collagen cross-link-ratio Pyr/deDHLNL indicates, that T3 modulated cross-link maturation in the MC3T3-E1 culture system. These results demonstrate that T3 directly regulates collagen synthesis and collagen cross-linking by up-regulating gene expression of the specific cross-link related enzymes, and underlines the importance of a well-balanced concentration of thyroid hormones for maintenance of bone quality.

Diabetes and thyroid disorders

It has long been recognised that thyroid hormones have marked effects on glucose homeostasis. Glucose intolerance is associated with hyperthyroidism and most recently it was shown that hypothyroidism is characterised by insulin resistance. Although autoimmune thyroid disease is more prevalent in type 1 diabetes as a result of their common origin, in patients with type 2 diabetes the prevalence of hypothyroidism and hyperthyroidism is similar to that of the general population. However, in type 2 diabetic patients, the presence of the highly frequent sub-clinical forms of hyperthyroidism and hypothyroidism should be ruled out since they may be associated with higher cardiovascular risk. While there are no doubts about the therapeutic impact of normalising hypothyroidism and hyperthyroidism, the information available about the benefit of treating subclinical thyroid disease in diabetes remains insufficient.

A randomized controlled trial of the effect of thyroxine replacement on cognitive function in community-living elderly subjects with subclinical hypothyroidism: the Birmingham Elderly Thyroid study

CONTEXT

Subclinical hypothyroidism (SCH) and cognitive dysfunction are both common in the elderly and have been linked. It is important to determine whether T4 replacement therapy in SCH confers cognitive benefit.

OBJECTIVE

Our objective was to determine whether administration of T4 replacement to achieve biochemical euthyroidism in subjects with SCH improves cognitive function.

DESIGN AND SETTING

We conducted a double-blind placebo-controlled randomized controlled trial in the context of United Kingdom primary care.

PATIENTS

Ninety-four subjects aged 65 yr and over (57 females, 37 males) with SCH were recruited from a population of 147 identified by screening.

INTERVENTION

T4 or placebo was given at an initial dosage of one tablet of either placebo or 25 microg T4 per day for 12 months. Thyroid function tests were performed at 8-weekly intervals with dosage adjusted in one-tablet increments to achieve TSH within the reference range for subjects in treatment arm. Fifty-two subjects received T4 (31 females, 21 males; mean age 73.5 yr, range 65-94 yr); 42 subjects received placebo (26 females, 16 males; mean age 74.2 yr, 66-84 yr).

MAIN OUTCOME MEASURES

Mini-Mental State Examination, Middlesex Elderly Assessment of Mental State (covering orientation, learning, memory, numeracy, perception, attention, and language skills), and Trail-Making A and B were administered.

RESULTS

Eighty-two percent and 84% in the T4 group achieved euthyroidism at 6- and 12-month intervals, respectively. Cognitive function scores at baseline and 6 and 12 months were as follows: Mini-Mental State Examination T4 group, 28.26, 28.9, and 28.28, and placebo group, 28.17, 27.82, and 28.25 [not significant (NS)]; Middlesex Elderly Assessment of Mental State T4 group, 11.72, 11.67, and 11.78, and placebo group, 11.21, 11.47, and 11.44 (NS); Trail-Making A T4 group, 45.72, 47.65, and 44.52, and placebo group, 50.29, 49.00, and 46.97 (NS); and Trail-Making B T4 group, 110.57, 106.61, and 96.67, and placebo group, 131.46, 119.13, and 108.38 (NS). Linear mixed-model analysis demonstrated no significant changes in any of the measures of cognitive function over time and no between-group difference in cognitive scores at 6 and 12 months.

CONCLUSIONS

This RCT provides no evidence for treating elderly subjects with SCH with T4 replacement therapy to improve cognitive function.