When to treat mild hypothyroidism

Deciphering the roles of triiodothyronine (T3) and thyroid-stimulating hormone (TSH) on cardiac electrical remodeling in clinical and experimental hypothyroidism

Hypothyroidism is the most frequent endocrine pathology. Although clinical or overt hypothyroidism has been traditionally associated to low T3 / T4 and high thyrotropin (TSH) circulating levels, other forms exist such as subclinical hypothyroidism, characterized by normal blood T3 / T4 and high TSH. In its different forms is estimated to affect approximately 10% of the population, especially women, in a 5:1 ratio with respect to men. Among its consequences are alterations in cardiac electrical activity, especially in the repolarization phase, which is accompanied by an increased susceptibility to cardiac arrhythmias. Although these alterations have traditionally been attributed to thyroid hormone deficiency, recent studies, both clinical trials and experimental models, demonstrate a fundamental role of TSH in cardiac electrical remodeling. Thus, both metabolic thyroid hormones and TSH regulate cardiac ion channel expression in many and varied ways. This means that the different combinations of hormones that predominate in different types of hypothyroidism (overt, subclinic, primary, central) can generate different forms of cardiac electrical remodeling. These new findings are raising the relevant question of whether serum TSH reference ranges should be redefined.

A review of the endocrine disrupting effects of micro and nano plastic and their associated chemicals in mammals

Over the years, the vaste expansion of plastic manufacturing has dramatically increased the environmental impact of microplastics [MPs] and nanoplastics [NPs], making them a threat to marine and terrestrial biota because they contain endocrine disrupting chemicals [EDCs] and other harmful compounds. MPs and NPs have deleteriouse impacts on mammalian endocrine components such as hypothalamus, pituitary, thyroid, adrenal, testes, and ovaries. MPs and NPs absorb and act as a transport medium for harmful chemicals such as bisphenols, phthalates, polybrominated diphenyl ether, polychlorinated biphenyl ether, organotin, perfluorinated compounds, dioxins, polycyclic aromatic hydrocarbons, organic contaminants, and heavy metals, which are commonly used as additives in plastic production. As the EDCs are not covalently bonded to plastics, they can easily leach into milk, water, and other liquids affecting the endocrine system of mammals upon exposure. The toxicity induced by MPs and NPs is size-dependent, as smaller particles have better absorption capacity and larger surface area, releasing more EDC and toxic chemicals. Various EDCs contained or carried by MPs and NPs share structural similarities with specific hormone receptors; hence they interfere with normal hormone receptors, altering the hormonal action of the endocrine glands. This review demonstrates size-dependent MPs' bioaccumulation, distribution, and translocation with potential hazards to the endocrine gland. We reviewed that MPs and NPs disrupt hypothalamic-pituitary axes, including the hypothalamic-pituitary-thyroid/adrenal/testicular/ovarian axis leading to oxidative stress, reproductive toxicity, neurotoxicity, cytotoxicity, developmental abnormalities, decreased sperm quality, and immunotoxicity. The direct consequences of MPs and NPs on the thyroid, testis, and ovaries are documented. Still, studies need to be carried out to identify the direct effects of MPs and NPs on the hypothalamus, pituitary, and adrenal glands.

Subclinical Hypothyroidism and Associated Cardiovascular Risk Factor in Perimenopausal Females

Background

Perimenopause refers to the period around menopause (40-55 years). This includes the period before menopause and the first year after menopause. Perimenopausal age is an important stage in a women's life. Many women are diagnosed with hypothyroidism at midlife. Hypothyroidism - both overt and subclinical are associated with increased risk of CVS diseases. Subclinical hypothyroidism is more important as this stage is usually ignored from treatment point of view and if early intervention is done in SCH worsening of metabolic derangement may be avoided.

Objectives

The present study was aimed to know the prevalence of subclinical hypothyroidism and associated dyslipidemia in perimenopausal females.

Material and Methods

In our retrospective study we took 100 perimenopausal females (40-55years) who were investigated for thyroid and lipid profile. Atherogenic indices like TC/HDL-c, LDL-c/HDL-c, TG/HDL-c ratios were calculated from the individual lipid profile parameters. The reference guidelines for lipid profile was according to NCEP ATP III.

Result

Subclinical hypothyroidism was found to be present in 18% of perimenopausal females The mean TSH levels were found to be higher in SCH as compared to euthyroid females with a mean value of 7.56±3.54(μIU/ ml). Dyslipidemia was seen in patients with SCH. TSH levels were found to be positively correlated with total cholesterol.

Conclusion

We conclude that subclinical hypothyroidism is present in 18% females of perimenopausal age group. Increased TSH levels are associated with hypertension, hypertriglyceridemia, and elevated TC/HDL-C ratio and non cholesterol HDL. In perimenopausal women the condition is usually underdiagnosed and ignored but subclinical hypothyroidism in these females should be screened and treated timely to decrease the risk of accelerated atherosclerosis and premature coronary artery disease in them.

A rare cause of subclinical hypothyroidism: macro-thyroid-stimulating hormone

Background Subclinical hypothyroidism is a situation in which the thyroid-stimulating hormone (TSH) value exceeds the upper limit of normal, but the free triiodothyronine (T3) and thyroxine (T4) values are within the normal range. The etiology is similar to overt hypothyroidism. Case presentation An 18-year-old female patient was referred to our endocrinology clinic due to elevated TSH levels detected during a routine examination. She was clinically euthyroid and had a normal thyroid ultrasound pattern. The TSH concentration was measured twice independently, giving values of 5.65 μIU/mL and 5.47 μIU/mL. The polyethylene glycol (PEG) method for TSH measurement was used to determine the concentration of macro-TSH (m-TSH), a macromolecule formed between TSH and immunoglobulin (Ig). Using the same blood samples for which the TSH levels were found to be high, the PEG method found TSH levels to be within a normal range, with values of 1.50 μIU/mL (5.65-1.50 μIU/mL measured; a decrease of 75%) and 1.26 μIU/mL (5.47-1.26 μIU/mL measured; a decrease of 77%), respectively. The TSH values determined by the PEG precipitation test were markedly low, with PEG-precipitable TSH ratios greater than 75%. Conclusions The cause of 55% of subclinical hypothyroidism is chronic autoimmune thyroiditis. However, it is necessary to exclude other TSH-elevated conditions for diagnosis. One of these conditions is m-TSH, which should be kept in mind even though it is rarely seen. m-TSH should be considered especially in patients who have a TSH value above 10 μIU/mL without hypothyroidism symptoms or who require a higher levothyroxine replacement dose than expected to make them euthyroid.

The Effects of Dyslipidemia in Subclinical Hypothyroidism

Background

Subclinical hypothyroidism (SCH) affects 7.5-8.5% of women and 2.8-4.4% of men globally. Usually, both hypothyroidism and hyperthyroidism are related to cardiovascular and cerebrovascular disease development. The relationship between subclinical hypothyroidism and dyslipidemia has been widely investigated, but the findings remain controversial. Recent evidence shows that serum thyroxine (T4) replacement therapy may improve lipid profiles. The objective of the present study is to assess dyslipidemia among patients with SCH in Benghazi, Libya and compare it with controls.

Methods

The study was conducted from August 2018 to November 2018 and included 36 patients with SCH. All the patients were around 30 years of age. We also included sex-matched healthy subjects (controls) selected from three diabetes and endocrinology clinics in Benghazi: Alhaya clinic, Alrazy clinic, and Alnukbah clinic. Clinical information and medical history were obtained through a questionnaire from all SCH patients and normal control subjects. Blood samples were collected and analyzed for thyroid-stimulating hormone (TSH), free thyroxine (FT4), total cholesterol (T-Chol), serum triglycerides (STG), low-density lipoprotein-cholesterol (LDL-C), and high-density lipoprotein-cholesterol (HDL-C).

Results

Patients with SCH showed significantly higher T-Chol, STG, and LDL-C levels, as well as significantly lower levels of HDL-C in comparison to the healthy controls. No significant correlation was found between TSH and T-Chol, STG, HDL-C, and LDL-C; no significant correlation was found between FT4 and HDL-C either. However, a strong negative correlation was found between FT4 and T-Chol, STG, and LDL-C.

Conclusion

Our study concluded that SCH is associated with dyslipidemia. We strongly recommend biochemical screening for thyroid dysfunction for all patients with dyslipidemia.

Subclinical hypothyroidism is not a risk factor for polycystic ovary syndrome in obese women of reproductive age

Obese women are at high risk for polycystic ovary syndrome (PCOS). Subclinical hypothyroidism (SCH) has been associated with weight gain, insulin resistance and impaired fertility, which are also factors involved in PCOS. However, there is limited information regarding the influence of SCH on the presence of PCOS. In order to determine whether SCH increases the prevalence of PCOS, we performed a cross-sectional study in a cohort of reproductive-aged obese women. All subjects underwent anthropometric evaluation, laboratory tests and ultrasound examination. Diagnosis of PCOS was based on the Rotterdam criteria. A total of 534 obese women were included and 108 (20.2%) of them were diagnosed with SCH. Patients with SCH showed similar insulin resistance, comparable androgen levels, and higher triglycerides levels (1.7 vs. 1.5 mmol/L, p = .002) compared to those with normal thyroid status. The frequency of PCOS did not differ between the two groups (56.1% for normal thyroid function vs. 60.2% for subclinical hypothyroidism, p = .514). In logistic regression analysis, SCH was not an independent risk factor for PCOS after adjusting for confounding factors (OR = 0.984, 95% CI 0.581-1.667). For the first time, our results suggest that SCH does not increase the risk of PCOS in obese women of reproductive age.

Estimation of serum prolactin levels and determination of prevalence of hyperprolactinemia in newly diagnosed cases of subclinical hypothyroidism

Background:

Hyperprolactinemia is a common endocrine disorder involving hypothalamic–pituitary axis. Prolactin (PRL) secretion is stimulated by dopamine antagonism and thyroid-releasing hormone. Hyperprolactinemia has been reported in subclinical hypothyroidism (SCH) but results are markedly variable and studies on SCH are very few. The objective of this study was to find out prevalence of hyperprolactinema in newly diagnosed subclinical hypothyroid patients.

Materials and Methods:

In this cross-sectional study, serum PRL levels of 150 newly diagnosed subclinical hypothyroid patients were determined using electrochemiluminescence method.

Results:

Raised PRL levels were found in 18 (%) patients with SCH. There was positive correlation between serum thyroid-stimulating hormone and PRL levels. Prevalence of infertility was significantly higher with presence of hyperprolactinemia than normoprolactinemia in subclinical hypothyroid patients.

Conclusion:

Routine prolactin estimation and subsequent treatment is required in patients with subclinical hypothroidism.

Evaluation of Tp-e interval, Tp-e/QT ratio and Tp-e/QTc ratio in patients with subclinical hypothyroidism

BACKGROUND

Prolongation of the peak-to-end interval of the T wave (Tp-e) has been reported as associated with ventricular arrhythmias. The aim of this study was to investigate the ventricular repolarization by using the Tp-e interval, Tp-e/QT ratio and Tp-e/ QTc ratio in patients with subclinical hypothyroidism (SH).

METHODS

We studied 56 volunteers: These were 28 patients with SH (mean age 45 ± 11 years) and 28 healthy subjects (mean age 34 ± 8 years). All basic biochemical parameters were analyzed and electrocardiograms (ECGs) were recorded. RR and QT intervals, QTc, Tp-e intervals and the Tp-e/QT and Tp-e/QTc ratios were calculated. The categorical and numerical variables were compared using the chi-square test and independent t test, respectively. Correlations were analyzed using the Spearman and Pearson correlation tests.

RESULTS

We found no difference between QT and QTc intervals between groups. In the subjects with SH, the Tp-e intervals (87 ± 5 ms, 66 ± 5 ms, p< 0.01), Tp-e/ QT ratio (0.23 ± 0.03, 0.18 ± 0.01, p< 0.01) and Tp-e/QTc ratio (0.21 ± 0.02, 0.16 ± 0.01, p< 0.01) were increased compared with healthy subjects. We also found positive correlations between levels of thyroid stimulating hormone (TSH) and Tp-e (r = 0.72, p< 0.01), Tp-e/ QT ratio (r = 0.67 p< 0.01), Tp-e/ QTc ratio (r = 0.68, p< 0.01). In the subjects with SH, Left Ventricular Myocardial Performance Index (LV-MPI) was increased compared with the healthy subjects (0.64 ± 0.08, 0.59 ± 0.09, p = 0.066) although it was not significant.

CONCLUSIONS

Compared with healthy subjects, patients with SH demonstrated longer Tp-e intervals, and higher Tp-e/QT and Tp-e/QTc ratios. TSH levels were positively correlated with Tp-e interval, Tp-e/QT ratio, and Tp-e/QTc ratio.

Association of thyroid peroxidase antibody and dyslipidemia in subclinical hypothyroidism

Context:

Subclinical hypothyroidism (SCH) is stated as mild thyroid failure, is more common as compared to overt hypothyroidism, is associated with different biochemical abnormalities such as dyslipidemia, and is also having high conversion rate into overt hypothyroidism in patients having thyroid peroxidase (TPO) antibody positive. Lipid abnormalities are controversial in SCH and there is lack of Indian studies showing correlation between lipid abnormalities and TPO positivity in SCH. Hence, we did this study to find the TPO positivity and associated dyslipidemia in SCH patients.

Materials and Methods:

It was a prospective observational study from January 2015 to December 2015 including fifty adult diagnosed SCH patients presented in outpatient department of Sri Balaji Action Medical Institute, Paschim Vihar, New Delhi. TPO positivity and different lipid abnormalities were studied in those fifty diagnosed SCH patients, and finally, association between TPO antibody and dyslipidemia was calculated.

Results:

Females were predominant (86%). TPO was positive in 56% SCH patients. Dyslipidemia was found in 100% of SCH patients with positive TPO antibody. In overall, TPO positive patients as well as TPO positive females, total cholesterol, triglyceride, and low-density lipoprotein were significantly high while high-density lipoprotein was insignificant. In males, no significant association was found.

Conclusion:

In SCH patients, dyslipidemia is significantly associated with TPO positivity, especially in females. Hence, early screening, diagnosis, and treatment of SCH patients are recommended to prevent further risks.

Effects of levothyroxine replacement therapy on parameters of metabolic syndrome and atherosclerosis in hypothyroid patients: a prospective pilot study

The aim of this study was to investigate the effect of levothyroxine (LT4) replacement therapy during three months on some parameters of metabolic syndrome and atherosclerosis in patients with increased thyroid-stimulating hormone (TSH) level. This study included a group of 30 female patients with TSH level >4 mIU/L and 15 matched healthy controls. Intima media complex thickness (IMCT) and peak systolic flow velocity (PSFV) of superficial femoral artery were determined by Color Doppler scan. In hypothyroid subjects, BMI, SBP, DBP, and TSH were significantly increased versus controls and decreased after LT4 administration. FT4 was significantly lower in hypothyroid subjects compared with controls and significantly higher by treatment. TC, Tg, HDL-C, and LDL-C were similar to controls at baseline but TC and LDL-C were significantly decreased by LH4 treatment. IMCT was significantly increased versus controls at baseline and significantly reduced by treatment. PSFV was similar to controls at baseline and significantly decreased on treatment. In this study, we have demonstrated the effects of LT4 replacement therapy during three months of treatment on correction of risk factors of metabolic syndrome and atherosclerosis.

Depressive symptoms in patients with subclinical hypothyroidism--the effect of treatment with levothyroxine: a double-blind randomized clinical trial

Despite the increasing evidence for relationships between thyroid dysfunction and neuropsychiatric alterations, the effect of treatment of thyroid disease on various clinical psychiatric outcomes is controversial. The purpose of this study was to investigate the effect of levothyroxine treatment on depressive symptoms in subjects with subclinical hypothyroidism. A randomized double-blind placebo-controlled clinical trial was performed. Sixty subjects (51 females and 9 males) with subclinical hypothyroidism were enrolled. Beck Depression Inventory was completed for all participants at the beginning of the study and 12 weeks after enrollment. The intervention and control groups received levothyroxine and placebo, respectively, for 12 weeks. There were no statistical differences in the total depression score and its subscales between the two groups at the beginning of the study. The Beck Depression Inventory score decreased from 16.79 ± 13.25 to 12.37 ± 10.01 (p value = 0.04) in the intervention group. The change in score was not significant for the control group (13.77 ± 11.71 to 11.86 ± 10.71; p value= 0.16). The affective subscale of Beck Depression Inventory did not change after 12 weeks of treatment with levothyroxine, while somatic subscale remarkably improved in the intervention group (p value = 0.02). This study showed the efficacy of treatment of subclinical hypothyroidism in people with levothyroxine in relation to depressive symptoms.

Association of thyroid-stimulating hormone and cardiovascular risk factors

Thyroid hormone plays an important role in regulating the lipid and glucose metabolism. Previously, much attention has been drawn to define the pathophysiological relationship between thyroid dysfunction and the incidence of cardiovascular diseases (CVDs). While the conditions of overt hypothyroidism and subclinical hypothyroidism were both emphasized, the association between CVD risks and the deregulated circulating thyroid-stimulating hormone (TSH) level remains to be elucidated. Nevertheless, multiple TSH-mediated physiological adaptations, including alteration of the serum lipids, body mass index, blood pressure and insulin sensitivity, have led to the difficulty of clearly examining the association between the TSH level and CVD prevalence. The current review aims to 1) summarize the evidence for the role of thyroid dysfunction and TSH abnormality in CVD pathogenesis and 2) explore the possible underlying molecular mechanisms of TSH-mediated cardiovascular pathology in hopes of providing better therapeutic strategies for the patients with deregulated TSH.

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.

Raised serum TSH in morbid-obese and non-obese patients: effect on the circulating lipid profile

Morbid obesity is associated with a high rate of raised serum TSH associated with normal free thyroid hormones. The body repercussions of this thyroid abnormality, suggesting subclinical hypothyroidism, are still debated. In particular, it is unclear whether the raised serum TSH of obesity results in changes of circulating lipids typically observed in hypothyroidism. Aim of this study was to evaluate the impact of a raised serum TSH on the lipid profile in morbid-obese and non-obese patients. Serum TSH, FT4, FT3, Tg-Ab, TPO-Ab and lipids were measured in 55 morbid-obese (BMI > 40 kg/m(2)) and 55 non-obese (BMI < 30 kg/m(2)) patients with a raised serum TSH. Despite similar serum levels of TSH, FT4 and FT3, morbid-obese patients displayed significantly lower mean levels of total cholesterol (200.8 ± 35.6 vs. 226.9 ± 41.4 mg/dl, p < 0.001) and a significantly lower prevalence of hypercholesterolemia (50.9 vs. 72.7 %, p < 0.01) when compared with non-obese patients. Morbid-obese patients also had lower mean serum HDL cholesterol and higher serum triglycerides. The impact of a raised serum TSH on the lipid profile differs in morbid-obese compared to non-obese patients, suggesting that obese patients might not be truly hypothyroid. Measuring total cholesterol could be a helpful tool for deciding whether a morbid-obese patient with a raised serum TSH should be given levothyroxine treatment.

Prevalence, clinical and biochemical profile of subclinical hypothyroidism in normal population in Mumbai

BACKGROUND

Subclinical Hypothyroidism (ScHt) affects 3-15% of the adult population. It's clinical and biochemical profile is not well defined, especially in Indian scenario. Our study aimed at screening normal population to define normative ranges of thyroid hormones and Serum thyroid stimulating hormone (S.TSH) and prevalence of ScHt and thyroid autoimmunity.

MATERIALS AND METHODS

Two-hundred thirty-seven normal subjects without family history of thyroid disease were evaluated for symptoms and laboratory tests for thyroid dysfunction and autoimmunity.

RESULTS

The thyroid function tests were as follows:

EUTHYROID GROUP

MEAN VALUES WERE: T3: 1.79 ± 0.42 ng/mL, T4: 10.23 ± 2.25 μg/dL, FT3: 1.88 ± 0.19 pg/mL, FT4: 1.12 ± 0.21 ng/dL, S.TSH: 2.22 ± 1.06 μlu/mL. 10.2% of euthyroid subjects had antimicrosomal antibodies (AMA) +ve (mean titer 1:918) and 23.6% were anti-thyroid peroxidase autoantibody (anti-TPO) +ve (mean titer 15.06 Au/mL). The euthyroid outlier range for S.TSH was 0.3-4.6 μlu/mL. The values were comparable in both the sexes. Those with S.TSH ≥ 5 μlu/mL were defined to have ScHt.

SCHT GROUP

Prevalence of ScHt was 11.3% (M:F ratio 1:3.7). 74% belonged to 35-54 years age group and prevalence increased with age (post-menopausal females: prevalence 20%). S.TSH was 9.8 ± 7.22 μlu/mL, mean S.AMA was 1:5079 (40.7% positivity) and mean S.anti-TPO was 260 Au/mL (47.6% positivity). Majority were agoitrous (74%), and stage I goiter was seen in 26% of this population. Symptom score of 5-8 was seen in 55% ScHt subjects versus 35% normal subjects.

CONCLUSION

Mean S.TSH in our population was 2.22 μlu/mL (euthyroid outliers: 0.3-4.6 μlu/mL); hence, S.TSH above 4.6 μlu/mL should be considered as abnormal. The prevalence of thyroid autoimmunity increases after age of 35 years. ScHt presents mainly in agoitrous form and with positive antibodies, suggesting autoimmunity as the cause.

Generic and brand-name L-thyroxine are not bioequivalent for children with severe congenital hypothyroidism

CONTEXT

In the United States, generic substitution of levothyroxine (L-T(4)) by pharmacists is permitted if the formulations are deemed to be bioequivalent by the Federal Drug Administration, but there is widespread concern that the pharmacokinetic standard used is too insensitive.

OBJECTIVE

We aimed to evaluate the bioequivalence of a brand-name L-T(4) (Synthroid) and an AB-rated generic formulation (Sandoz, Princeton, NJ) in children with severe hypothyroidism.

DESIGN

This was a prospective randomized crossover study in which patients received 8 weeks of one L-T(4) formulation followed by 8 weeks of the other.

SETTING

The setting was an academic medical center.

PATIENTS

Of 31 children with an initial serum TSH concentration >100 mU/L, 20 had congenital hypothyroidism (CH), and 11 had autoimmune thyroiditis.

MAIN OUTCOME MEASURES

The primary endpoint was the serum TSH concentration. Secondary endpoints were the free T(4) and total T(3) concentrations.

RESULTS

The serum TSH concentration was significantly lower after 8 weeks of Synthroid than after generic drug (P = .002), but thyroid hormone levels did not differ significantly. Subgroup analysis revealed that the difference in TSH was restricted to patients with CH (P = .0005). Patients with CH required a higher L-T(4) dose (P < .0004) and were younger (P = .003) but were not resistant to thyroid hormone; 15 of 16 CH patients had severe thyroid dysgenesis or agenesis on imaging. The response to generic vs brand-name preparation remained significant when adjusted for age.

CONCLUSIONS

Synthroid and an AB-rated generic L-T(4) are not bioequivalent for patients with severe hypothyroidism due to CH, probably because of diminished thyroid reserve. It would therefore seem prudent not to substitute L-T(4) formulations in patients with severe CH, particularly in those <3 yr of age. Our results may have important implications for other severely hypothyroid patients in whom precise titration of L-T(4) is necessary.

Preservation of renal function by thyroid hormone replacement therapy in chronic kidney disease patients with subclinical hypothyroidism

CONTEXT

Subclinical hypothyroidism is not a rare condition, but the use of thyroid hormone to treat subclinical hypothyroidism is an issue of debate.

OBJECTIVE

This study was undertaken to investigate the impact of thyroid hormone therapy on the changes in estimated glomerular filtration rate (eGFR) in subclinical hypothyroidism patients with stage 2-4 chronic kidney disease.

PATIENTS

A total of 309 patients were included in the final analysis.

MAIN OUTCOME MEASURE

The changes in eGFR over time were compared between patients with and without thyroid hormone replacement therapy using a linear mixed model. Kaplan-Meier curves were constructed to determine the effect of thyroid hormone on renal outcome, a reduction of eGFR by 50%, or end-stage renal disease. The independent prognostic value of subclinical hypothyroidism treatment for renal outcome was ascertained by multivariate Cox regression analysis.

RESULTS

Among the 309 patients, 180 (58.3%) took thyroid hormone (treatment group), whereas 129 (41.7%) did not (nontreatment group). During the mean follow-up duration of 34.8 ± 24.3 months, the overall rate of decline in eGFR was significantly greater in the nontreatment group compared to the treatment group (-5.93 ± 1.65 vs. -2.11 ± 1.12 ml/min/yr/1.73 m(2); P = 0.04). Moreover, a linear mixed model revealed that there was a significant difference in the rates of eGFR decline over time between the two groups (P < 0.01). Kaplan-Meier analysis also showed that renal event-free survival was significantly lower in the nontreatment group (P < 0.01). In multivariate Cox regression analysis, thyroid hormone replacement therapy was found to be an independent predictor of renal outcome (hazard ratio, 0.28; 95% CI, 0.12-0.68; P = 0.01).

CONCLUSION

Thyroid hormone therapy not only preserved renal function better, but was also an independent predictor of renal outcome in chronic kidney disease patients with subclinical hypothyroidism.

Are hsCRP Levels and LDL/HDL Ratio Better and Early Markers to Unmask Onset of Dyslipidemia and Inflammation in Asymptomatic Subclinical Hypothyroidism?

The implications of subclinical hypothyroidism (SCH) are many amongst which the most important is progression to overt hypothyroidism. Other debatable aspects are its association with cardiovascular risk, neuromuscular and psychiatric dysfunction, increased predisposition to developing metabolic syndrome and an underlying pro-inflammatory state. We aimed to study the lipid profile, lipoprotein(a) [Lp(a)] and hsCRP levels and insulin resistance in a group of patients with SCH in a referral hospital and see if any significant differences exist between them and euthyroids. This is a case-control study where the selection of controls and cases was based on the thyroid profile. Subjects were selected on their visit to clinical biochemistry lab for thyroid function tests. 33 euthyroids were taken as controls (Group I) and 38 patients comprising of subclinical hypothyroids were grouped as cases (Group II). Serum thyroid stimulating hormone (TSH) was in the range of 0.5-5.0 mIU/L for euthyroids and for subclinical hypothyroids the concentration of TSH was more than 5 mIU/L. The concentration of tri-iodothyronine (T3) and thyroxine (T4) were in normal reference range in both the groups. Individual lipid profile parameters failed to show a significant p value between cases and controls. The LDL/HDL ratio was highly significant (p value < 0.0001) and hsCRP was also statistically between the two groups (p value = 0.0054). Lp(a) and insulin resistance did not differ significantly. SCH is a common disorder that frequently progresses to overt hypothyroidism. This study underlines the importance of LDL/HDL ratio rather than measurement of individual lipid profile parameters in bringing to light the dyslipidemic state associated with SCH. Moreover the use of hsCRP to detect an underlying pro-inflammatory state in SCH can also be emphasized.

Thyroid disrupting chemicals in plastic additives and thyroid health

The globally escalating thyroid nodule incidence rates may be only partially ascribed to better diagnostics, allowing for the assessment of environmental risk factors on thyroid disease. Endocrine disruptors or thyroid-disrupting chemicals (TDC) like bisphenol A, phthalates, and polybrominated diphenyl ethers are widely used as plastic additives in consumer products. This comprehensive review studied the magnitude and uncertainty of TDC exposures and their effects on thyroid hormones for sensitive subpopulation groups like pregnant women, infants, and children. Our findings qualitatively suggest the mixed, significant (α = 0.05) TDC associations with natural thyroid hormones (positive or negative sign). Future studies should undertake systematic meta-analyses to elucidate pooled TDC effect estimates on thyroid health indicators and outcomes.

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.

Favorable influence of subclinical hypothyroidism on the functional outcomes in stroke patients

Subclinical hypothyroidism (SCH) is thought to have an influence on stroke outcomes. However, few reports demonstrate a favorable relationship between the two. We evaluated this association in acute ischemic stroke. From Jan 2005 to June 2008, 756 acute ischemic stroke patients were recruited within seven days of onset. The patients with overt hypothyroidism/hyperthyroidism or other medical conditions that may affect thyroid function were excluded. Thyroid stimulating hormone (TSH) and free thyroxine (FT4) levels were measured within two days. Patients were divided into two groups: the SCH group (TSH > 5.0 microU/mL and normal FT4 levels) and the control group. Stroke outcomes were assessed using two different criteria. In the first outcome model, favorable outcomes [I] were simply defined by modified Rankin Scale (mRS) scores (<or= 1), while the favorable outcomes [II] were defined as follows: a) a mRS score of 0, if the baseline National Institute of Health Stroke Scale (NIHSS) scores were < 8, b) a mRS score of 0 or 1, if the NIHSS scores were 8-14, c) a mRS score 0-2, if the NIHSS scores were >14. The changes in mRS scores and the proportion of patients with favorable outcomes [I] or [II] at the 30(th) and 90(th) day were compared between the two patient groups. Of the 756 patients, 31 (4.1%) were patients with SCH. More patients from the SCH group showed improvement in NIHSS scores on the 30(th) day compared to the control group (48.4% vs. 25.3%, p=.006). In addition, the proportion of patients who exhibited favorable outcomes [I] was significantly higher in the SCH group on the 90(th) day (74.2% vs. 55.3%, p=.027) and that trend was seen as early as the 30(th) day (p=.102). Similarly, the proportion of the patients with favorable outcomes [II] was significantly greater in the SCH group both on the 30(th) (29.0% vs. 14.6%, p=.039) and 90(th) day (58.0% vs. 31.0%, p=.003). We found that acute ischemic stroke patients with SCH at admission were more likely to show favorable functional outcomes than those without SCH. We can suggest preconditioning before the stroke combined with a reduced response to stress as a possible protective mechanism.

Lipid profiles in the untreated patients with Hashimoto thyroiditis and the effects of thyroxine treatment on subclinical hypothyroidism with Hashimoto thyroiditis

To evaluate the prevalence of dyslipidemia in the population of Hashimoto thyroiditis, we reviewed medical records on the consecutive 1181 cases with adult Hashimoto thyroiditis and 830 cases were adopted for the study. First, the serum TSH level increased and serum free T4 level decreased, slightly but significantly, with increasing age. There were significant positive correlations between serum TSH levels and lipid parameters such as total cholesterol (TC), triglyceride (TG), HDL-cholesterol (HDL-C), LDL-cholesterol (LDL-C), non-HDL-C and LDL-C/HDL-C ratio (L/H). In contrast, there were significant negative correlations between serum free T4 levels and all of these lipid parameters. According to the thyroid function, the cases were classified into 4 groups such as thyrotoxicosis (TT), euthyroidism (EU), subclinical hypothyroidism (SH) and overt hypothyroidism (OH). TC, HDL-C, non-HDL-C and LDL-C of TT were significantly lower than those in EU. In contrast, TC, TG, non-HDL-C, LDL-C, L/H and age of OH were significantly higher than those in EU. Interestingly, LDL-C and L/H of SH were significantly higher compared with EU. Thirty-two of SH patients were treated with small doses of levothyroxine and the effects on the lipid profile were examined. The TC, non-HDL-C, LDL-C and L/H were significantly decreased after treatment. In conclusion, the prevalence of dyslipidemia increases along with hypofunction of the thyroid and T4 replacement therapy may improve lipid profile in the cases of SH with Hashimoto thyroiditis.

Effect of levothyroxine treatment on QT dispersion in patients with subclinical hypothyroidism

OBJECTIVE

To examine the effect of levothyroxine treatment in patients with subclinical hypothyroidism on electrocardiographic variables, especially on ventricular repolarization-related factors.

METHODS

Sixteen women (mean age, 48.2 years) with subclinical hypothyroidism were treated with levothyroxine for 16 weeks. All standard 12-lead electrocardiographic recordings were scanned and transferred to a computer, and the QT intervals were measured on 300 times magnified recordings. QT dispersion, which reflects the heterogeneity of the ventricular repolarization, was calculated by the difference between the QT maximum and the QT minimum.

RESULTS

We found that, after 16 weeks of levothyroxine treatment, the QT interval decreased from 387.2 +/- 10.8 ms to 345.6 +/- 13.0 ms (P<0.0001). The study patients exhibited a significant reduction of QT dispersion from 46.5 +/- 5.3 ms to 30.7 +/- 5.8 ms (P<0.0001). On linear regression analysis, a positive relationship was found between QT dispersion and logarithmic serum TSH levels (r = 0.492; P<0.0001).

CONCLUSION

We conclude that serum TSH concentration has a role in ventricular inhomogeneity and, therefore, that subclinical hypothyroidism may predispose to ventricular arrhythmias. A large-scale, multicenter, randomized trial should be undertaken to address the benefit-to-risk ratio of levothyroxine treatment on cardiac inhomogeneity in patients with subclinical hypothyroidism.

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.

Subclinical hypothyroidism: the state of the art

Subclinical hypothyroidism (SH) is a common clinical problem, particularly in adulthood and the elderly. Its prevalence is conditioned by several etiological and risk factors. The highest age- and sex-specific rates are in women over 60. SH may be associated with manifestations of mild thyroid failure, which may reverse under levothyroxine (L-T4) therapy. The risk of progression to overt hypothyroidism is distinctly higher in cases with underlying thyroid disease. A population routine screening is not generally recommended, but screening is encouraged in high-risk groups. L-T4 therapy may be indicated in subjects with TSH levels which are repeatedly and consistently elevated (>10 microIU/ml) and may be considered in those with TSH ranging between 4.5-5.5 and 10 microIU/ml, particularly if anti-thyroid antibodies are positive and/or hypothyroid symptoms are present. Treatment should be based, at least initially, on L-T4 low doses.

Thyroid hormone replacement for subclinical hypothyroidism

BACKGROUND

Subclinical hypothyroidism is defined as an elevated serum thyroid-stimulating hormone (TSH) level with normal free thyroid hormones values. The prevalence of subclinical hypothyroidism is 4% to 8% in the general population, and up to 15% to 18% in women who are over 60 years of age. There is considerable controversy regarding the morbidity, the clinical significance of subclinical hypothyroidism and if these patients should be treated.

OBJECTIVES

To assess the effects of thyroid hormone replacement for subclinical hypothyroidism.

SEARCH STRATEGY

We searched The Cochrane Library, MEDLINE, EMBASE and LILACS. Ongoing trials databases, reference lists and abstracts of congresses were scrutinized as well.

SELECTION CRITERIA

All studies had to be randomised controlled trials comparing thyroid hormone replacement with placebo or no treatment in adults with subclinical hypothyroidism. Minimum duration of follow-up was one month.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data. We contacted study authors for missing or additional information.

MAIN RESULTS

Twelve trials of six to 14 months duration involving 350 people were included. Eleven trials investigated levothyroxine replacement with placebo, one study compared levothyroxine replacement with no treatment. We did not identify any trial that assessed (cardiovascular) mortality or morbidity. Seven studies evaluated symptoms, mood and quality of life with no statistically significant improvement. One study showed a statistically significant improvement in cognitive function. Six studies assessed serum lipids, there was a trend for reduction in some parameters following levothyroxine replacement. Some echocardiographic parameters improved after levothyroxine replacement therapy, like myocardial relaxation, as indicated by a significant prolongation of the isovolumic relaxation time as well as diastolic dysfunction. Only four studies reported adverse events with no statistically significant differences between groups.

AUTHORS' CONCLUSIONS

In current RCTs, levothyroxine replacement therapy for subclinical hypothyroidism did not result in improved survival or decreased cardiovascular morbidity. Data on health-related quality of life and symptoms did not demonstrate significant differences between intervention groups. Some evidence indicates that levothyroxine replacement improves some parameters of lipid profiles and left ventricular function.

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.

Cardiovascular risk factors in patients with subclinical hypothyroidism

Background/Aims. Overt hypothyroidism is disease associated with accelerated arteriosclerosis and coronary heart disease. Whether subclinical hypothyroidism (SH) is associated with increased cardiovascular risk is contraversial. As SH is a high prevalence thyroid dysfunction, specially in older women, it is important to evaluate cardiovascular risk factors in these patients and that was the aim of this study. Methods. We examined 30 patients with SH and 20 healthy controls. Subclinical hypothireoidism was defined as an elevated thyrotropin (TSH) (> 4.5 mU/L) and normal free thyroxine (FT4) level. In all the participants we determined body mass index (BMI), blood pressure, TSH, FT4, antibodies to thyroid peroxidase, antibodies to thyroglobulin, total cholesterol, high density lipoprotein (HDL) cholesterol, low density lipoprotein (LDL) cholesterol, triglicerides, total cholesterol/HDL cholesterol ratio and LDL/HDL cholesterol ratio. Results. Mean BMI in patients with SH was significantly higher (p < 0.05), as well as diastolic blood pressure (p < 0.01) compared with the controls. Average levels of total cholesterol (5.40?0.62 vs 5.06?0.19 mmol/l, p < 0.01) and triglycerides (2.16?0.56 vs 1.89?0.24 mmol/l, p < 0.05) were also significantly higher in the group with SH. Individual analysis revealed that the percentage of patients with SH having borderline elevated total cholesterol (63.33%), hypertrigliceridemia (43.33%) and elevated total cholesterol/HDL cholesterol ratio (26.67%) were significantly higher than the percentage in the controls. No significant correlation between TSH and lipid parameters was detected. Conclusion. Subclinical hypothyroidism was associated with higher BMI, diastolic hypertension, higher total cholesterol and triglicerides levels and higher total cholesterol/HDL cholesterols ratio. This might increase the risk of accelerated arteriosclerosis in patients with SH.

Hypothyroidism as a protective factor in acute stroke patients

OBJECTIVE

It has been reported that hypothyroidism is associated with better survival in elderly persons. We investigated possible associations of thyroid status with clinical outcome in patients with acute stroke.

DESIGN

Retrospective analysis.

PATIENTS

Consecutive patients (median age 70 years) admitted for acute stroke.

MEASUREMENTS

Total T3, T4 and TSH levels. Stroke severity evaluation using the Scandinavian Stroke Scale (SSS) and the Glasgow Coma Score (GCS). Handicap and survival assessment over 12 months.

RESULTS

Of 744 patients where thyroid function tests were available within the first 24 h of stroke, 13 had elevated TSH (>or= 10 microU/ml; range 10-42 microU/ml) (hypo-group), 51 had mildly elevated TSH (3.3-9.9 microU/ml) and 680 had nonelevated TSH < 3.3 microU/ml. In the hypo-group transient ischaemic attacks (TIA's) were more prevalent (46.2%) compared to the groups of mildly elevated TSH (11.8%) and nonelevated TSH (12.4%, P < 0.002). Hypo-group had more frequently an adequate level of consciousness (GCS 14-15 = fully alert): 92.3%vs 74.5% and 63.7% (P = 0.033), a milder neurological deficit (SSS score 45-58) 76.9%vs 39.2% and 38.7% (P = 0.02) compared to the other two groups, respectively, and a tendency for lower glucose levels on admission. One year outcome tended to be better with respect to survival and handicap.

CONCLUSIONS

Acute stroke patients with laboratory findings compatible with pre-existing hypothyroidism on admission, appear to have better clinical presentation and outcome; we speculate that a reduced response to stress and previous TIA's, possibly related to endogenous 'preconditioning', may contribute to this phenomenon.

Neuropsychological function and symptoms in subjects with subclinical hypothyroidism and the effect of thyroxine treatment

OBJECTIVE

Our objective was to examine the relation between neuropsychological function and subclinical hypothyroidism (SHT), defined as serum TSH of 3.5-10.0 mIU/liter and normal serum free T4 and free T3 levels, and to study the effect of T4 supplementation.

SUBJECTS

A total of 89 subjects (45 males) with SHT and 154 control subjects (72 males) were recruited from a general health survey (the fifth Tromsø study). Sixty-nine of those with SHT were included in a placebo-controlled, double-blind intervention study with T4 medication for 1 yr.

MAIN OUTCOME MEASURES

We used fourteen tests of cognitive function, Beck Depression Inventory, General Health Questionnaire, and a questionnaire on hypothyroid symptoms.

RESULTS

The mean +/- sd serum TSH in the SHT and control group were 5.57 +/- 1.68 and 1.79 +/- 0.69 mIU/liter, respectively. There were no significant differences in cognitive function and hypothyroid symptoms between the two groups, but those with SHT scored significantly better than the controls on the GHQ-30. At the end of the intervention study, serum TSH in the T4 group (n = 36) and the placebo group (n = 33) were 1.52 +/- 1.51 and 5.42 +/- 1.96 mIU/liter, respectively. T4 substitution had no effect on any of the parameters measured.

CONCLUSION

In subjects with SHT where the serum TSH level is in the 3.5-10.0 mIU/liter range, there is no neuropsychological dysfunction, and compared with healthy controls, there is no difference in symptoms related to hypothyroidism.

Increased risk for atherosclerosis estimated by pulse wave velocity in hypothyroidism and its reversal with appropriate thyroxine treatment

Pulse wave velocity (PWV) is known to represent arterial stiffness and is established as a marker for cardiovascular risk and a prognostic factor for mortality in the case of chronic renal failure or hypertension. The application of an automated apparatus for measuring brachial-ankle pulse wave velocity (baPWV) has made PWV measurement non-invasive, easier to screen for cardiovascular risk and as a result, baPWV measurements have become widely applied in clinical practice in recent years. We assessed the baPWV in 7 flank hypothyroidism patients and 28 subclinical hypothyroidism patients. In comparison with age matched healthy controls, 3 hypothyroid patients had advanced values and by replacement therapy, all 7 subjects showed improvement in their baPWV values (1531.2 +/- 242.7 to 1330.2 +/- 208.6 cm/s, p<0.05). In 28 subclinical hypothyroid subjects, 71% also had accelerated baPWV values for their age. Ten subjects (36% of all) had neither hypertension, hyperlipidemia, diabetes nor were taking any medication, and yet 8 patients out of 10 showed advanced baPWV values compared to age matched mean values. The baPWV was not correlated to TSH or total cholesterol levels, and was associated with only age and blood pressure (p = 0.01, <0.001, respectively), which are widely demonstrated as the characteristics for baPWV. In two subclinical hypothyroid subjects, who were normotensive and had no dyslipidemia, thyroxine treatment was performed and the baPWV decreased with unchanged blood pressure and total cholesterol levels. We concluded that the arterial wall stiffness tends to be increased in both overt and subclinical hypothyroid patients, and an appropriate treatment could reverse the abnormalities. It is possible that the initiation of adequate treatment in subclinical hypothyroidism may reduce the cardiovascular risk.

Hypothyroidism

Hypothyroidism is common, potentially serious, often clinically overlooked, readily diagnosed by laboratory testing, and eminently treatable. The condition is particularly prevalent in older women, in whom autoimmune thyroiditis is common. Other important causes include congenital thyroid disorders, previous thyroid surgery and irradiation, drugs such as lithium carbonate and amiodarone, and pituitary and hypothalamic disorders. Worldwide, dietary iodine deficiency remains an important cause. Hypothyroidism can present with nonspecific constitutional and neuropsychiatric complaints, or with hypercholesterolaemia, hyponatraemia, hyperprolactinaemia, or hyperhomocysteinaemia. Severe untreated hypothyroidism can lead to heart failure, psychosis, and coma. Although these manifestations are neither specific nor sensitive, the diagnosis is confirmed or excluded by measurements of serum thyrotropin and free thyroxine. Thyroxine replacement therapy is highly effective and safe, but suboptimal dosing is common in clinical practice. Patient noncompliance, drug interactions, and pregnancy can lead to inadequate treatment. Iatrogenic thyrotoxicosis can cause symptoms, and, even when mild, provoke atrial fibrillation and osteoporosis. We summarise present understanding of the history, epidemiology, pathophysiology, and clinical diagnosis and management of hypothyroidism.

5: Diagnosis and management of hyperthyroidism and hypothyroidism

The most common cause of hyperthyroidism in Australia is Graves disease, caused by a defect in immunoregulation in genetically predisposed individuals, leading to production of thyroid-stimulating antibodies. Each of the three modalities of therapy for Graves disease--thionamide drugs, subtotal or total thyroidectomy, and radioactive iodine ablation--can render the patient euthyroid, but all have potential adverse effects and may not eliminate recurrences. Hypothyroidism occurs in about 5% of the adult population; most present with "subclinical" hypothyroidism (mild thyroid failure), characterised by raised levels of serum thyroid stimulating hormone (TSH) but normal free thyroxine (T(4)). The most common cause of hypothyroidism in Australia is autoimmune chronic lymphocytic thyroiditis, characterised by raised circulating levels of thyroid peroxidase antibody. Symptoms and signs of hypothyroidism are often mild or subtle and, when there is clinical suspicion, thyroid function tests are needed; if serum TSH level is raised, free T(4) and thyroid peroxidase antibody should be measured. Replacement therapy with thyroxine is the cornerstone of therapy (1.6 microg/kg lean body weight daily, taken on an empty stomach); combination therapy with thyroxine and liothyronine (T(3)) is promoted, but there is little evidence of its clinical benefit. Despite the development of highly sensitive laboratory tests, clinical assessment and judgement remain paramount

Disfunções mínimas da tiróide: hipotiroidismo subclínico e hipertiroidismo subclínico

Hipotiroidismo subclínico (SHT) e hipertiroidismo subclínico (SCH) são definidos pelas concentrações normais de T4 e T3 livres séricos associadas com valores de TSH elevado (SHT) ou suprimido (SCH). As prevalências são baixas e sintomas e sinais de disfunção tiroideana escassos. No SHT, colesterol total e LDL-C estão ligeiramente elevados, e tratamento com levotiroxina pode influir nos valores dos lipídeos. Ocorre diminuição da contratilidade do miocárdio e aumento da resistência vascular periférica, que melhoram com o tratamento. Fibrilação atrial é mais freqüente no SCH, e há aumento do índice de massa do ventrículo esquerdo, da contratilidade cardíaca, disfunção diastólica e indução de batimentos atriais ectópicos que regridem com uso de beta-bloqueadores. No SCH, ocorre diminuição da densidade óssea. Depressão, doença do pânico e alterações de testes cognitivos são freqüentes no SHT. O tratamento do SHT é indicado com TSH sérico maior do que 8mU/L e presença de anticorpos antitiroideanos, e do SCH endógeno, quando existem sintomas, em idosos ou concentração de TSH menor do que 0,1mU/L.

Development of a murine model of autoimmune thyroiditis induced with homologous mouse thyroid peroxidase

Autoimmune thyroid disease (AITD) is a common autoimmune disease. Thyroid peroxidase (TPO) is a well characterized autoantigen in AITD. Autoantibodies and autoreactive T lymphocytes to TPO are believed to play a major role in the pathogenesis of lymphocytic thyroiditis. To understand the pathogenic mechanisms of AITD and the role of TPO, we have established a mouse model of lymphocytic thyroiditis by immunizing C57Bl/6 (H-2(b)), CBA (H-2(k)), and C57Bl/6 x CBA F1 mice with recombinant murine TPO (rmTPO) ectodomain comprising amino acid residue 1-837 produced in Escherichia coli. Mice were immunized with 30 microg purified ectodomain in complete Freund's adjuvant. Antibodies against rmTPO were detected in the serum of all mice from day 21 onward. Draining lymph node cells from rmTPO-immunized animals showed dose-dependent proliferation to TPO stimulation. Mice killed at d 50 and 90 revealed variable degrees of thyroiditis with infiltration of mononuclear cells and destruction of thyroid follicles. C57Bl/6 and the F1 mice, in comparison with CBA mice, showed a greater degree of thyroiditis. There was a lack of correction between the intensity of thyroiditis and the anti-TPO response. Immunotyping of the thyroid cellular infiltrates showed predominantly CD4+ T cells and B220+ B cells but scanty CD8+ T cells. None of the control mice injected with the purified fusion partner developed anti-TPO antibodies and thyroiditis. In conclusion, a genuine autoimmune mouse model of lymphocytic thyroiditis was established using autologous mouse TPO. This new model induced with autologous TPO will lead to a better understanding of the mechanisms in destructive thyroiditis and will assist in the development of new strategies for modulating the pathogenic immune response.

Humic substances in drinking water and the epidemiology of thyroid disease

Thyroid diseases are common in all populations but the type and frequency depends on environmental factors. In Denmark geographical differences in iodine intake are caused by different iodine contents of drinking water, which varies from < 1 to 139 microg iodine per litre. Comparative epidemiologic studies have demonstrated considerable differences in type and occurrence of thyroid disease with more goitre and hyperthyroidism in Aalborg with water iodine content around 5 microg/L, and more hypothyroidism in Copenhagen with water iodine around 20 microg/L. In Denmark, iodine in ground water is bound in humic substances, which have probably leached from marine sediments in the aquifers. Interestingly, humic substances in water from other parts of the world have goitrogenic properties, especially humic substances from coal and shale. Humic substances are heterogeneous mixtures of naturally occurring molecules, produced by decomposition of plant and animal tissues. The effect of humic substances in drinking water on the epidemiology of thyroid disease probably depends on the source of aquifer sediments.

Serum thyroid-stimulating hormone measurement for assessment of thyroid function and disease

Third generation thyroid stimulating hormone (TSH) assays have emerged as the single most useful test of thyroid function, and are used widely and appropriately as a screening test. TSH measurement alone may be misleading in complicated patients and those undergoing treatment for thyroid dysfunction. Before obtaining thyroid function tests, clinicians need to consider whether the patient might have pituitary or hypothalamic disease or severe nonthyroidal illness, and whether assessment of the pituitary-thyroid axis reflects steady-state conditions. Subclinical hyperthyroidism is associated with adverse effects on the skeleton and the heart, and is best assessed by measurement of serum TsH with a third-generation assay.