Type 3 deiodinase and consumptive hypothyroidism: a common mechanism for a rare disease

Thyroid hormone deficiency affects anxiety-related behaviors and expression of hippocampal glutamate transporters in male congenital hypothyroid rat offspring

Thyroid hormones are crucial for brain development and their deficiency during fetal and postnatal periods can lead to mood and cognitive disorders. We aimed to examine the consequences of thyroid hormone deficiency on anxiety-related behaviors and protein expression of hippocampal glutamate transporters in congenital hypothyroid male offspring rats. Possible beneficial effects of treadmill exercise have also been examined. Congenital hypothyroidism was induced by adding propylthiouracil (PTU) to drinking water of pregnant Wistar rats from gestational day 6 until the end of the weaning period (postnatal day 28). Next, following 4 weeks of treadmill exercise (5 days per week), anxiety-related behaviors were examined using elevated plus maze (EPM) and light/dark box tests. Thereafter, protein expression of astrocytic (GLAST and GLT-1) and neuronal (EAAC1) glutamate transporters were measured in the hippocampus by immunoblotting. Hypothyroid rats showed decreased anxiety-like behavior, as measured by longer time spent in the open arms of the EPM and in the light area of the light/dark box, compared to control rats. Hypothyroid rats had significantly higher GLAST and GLT-1 and lower EAAC1 protein levels in the hippocampus than did the euthyroid rats. Following exercise, anxiety levels decreased in the euthyroid group while protein expression of EAAC1 increased and returned to normal levels in the hypothyroid group. Our findings indicate that thyroid hormone deficiency was associated with alterations in protein expression of glutamate transporters in the hippocampus. Up-regulation of hippocampal GLAST and GLT-1 could be at least one of the mechanisms associated with the anxiolytic effects of congenital hypothyroidism.

Refractory Hypothyroidism: Unraveling the Complexities of Diagnosis and Management

INTRODUCTION

Refractory hypothyroidism (RH) represents a challenge in the diagnosis and treatment within the field of thyroidology. It is defined as the inability to achieve disease control despite using levothyroxine (LT4) doses of 1.9 μg/kg/d or higher.

METHODS

A comprehensive review, encompassing 103 articles, was conducted using the Scielo, Scopus, and EMBASE databases, providing an approach to evaluation and diagnosis of this condition.

RESULTS

LT4 disintegrates and dissolves within an acidic gastric environment before being absorbed in the jejunum and ileum. It then extensively binds to serum transporter proteins and undergoes deiodination to yield tri-iodothyronine, the biologically active hormone. There are various nonpathological causes of RH, such as noncompliance with treatment, changes in the brand of LT4, food and drug interferences, as well as pregnancy. Pathological causes include lactose intolerance, Helicobacter pylori infection, giardiasis, among others. The diagnosis of RH involves conducting a thorough medical history and requesting relevant laboratory tests to rule out causes of treatment resistance. The LT4 absorption test allows for the identification of cases of malabsorption. The treatment of RH involves identifying and addressing the underlying causes of noncompliance or malabsorption. In cases of pseudomalabsorption, supervised and weekly administration of LT4 may be considered.

DISCUSSION

Early recognition of RH and correction of its underlying cause are of utmost importance, as this avoids the use of excessive doses of LT4 and prevents cardiovascular and bone complications associated with this condition.

Deiodinase Type 3 Polymorphism (rs1190716) Affects Therapeutic Response to Levothyroxine

Objectives

Levothyroxine (LT4) is a commonly used treatment for hypothyroidism. Deiodinase enzymes control the metabolism and homeostasis of thyroid hormones (THs). Deiodinase type 3 gene (DIO3) encodes deiodinase type 3 enzyme (D3), and the genetic polymorphisms of this gene could affect the levels of THs and the response to LT4 treatment. This study aimed to investigate the single-nucleotide polymorphism (SNP), rs1190716; C > T, of DIO3 as a candidate genetic variant that might affect the clinical response to LT4 treatment.

Materials and Methods

Two hundred Iraqi hypothyroid female patients aged 40 years were enrolled in this cross-sectional study. All of them were already on the LT4 treatment for at least 4 months. THs [thyroxin (T4), triiodothyronine (T3), reverse triiodothyronine (rT3), and diiodothyronine (T2)] were estimated. An allele-specific polymerase chain reaction technique was performed to detect the rs1190716; C > T SNP.

Results

The genotypes distribution of rs1190716; C > T SNP was 10 (4.5%) for the wild type (CC), 50 (22.7%) for the heterozygous mutant type (TC), and 160 (72.7%) for the homozygous mutant type (TT). The patients were divided into three groups according to their genotypes. Significant differences were found in the T4, T3, and T2 levels among the patients (p=0.019, p=0.039, p=0.032, respectively).

Conclusion

The rs1190716; C > T SNP could affect the activity of the D3 enzyme and the metabolic homeostasis of the THs; therefore rs1190716; C > T SNP could have an impact on the therapeutic response to LT4 in Iraqi female patients with primary hypothyroidism. Regarding DIO3 gene, this is a novel finding; hence, further studies are needed to confirm it.

Tumor Microbial Communities and Thyroid Cancer Development-The Protective Role of Antioxidant Nutrients: Application Strategies and Future Directions

Thyroid cancer (TC), the most frequent malignancy of the endocrine system, has recorded an increasing incidence in the last decades. The etiology of TC remains at least partly unknown and, among modifiable risk factors, the gut microbiota and dietary nutrients (vitamins, essential microelements, polyphenols, probiotics) have been recognized to not only influence thyroid function, but exert critical effects on TC development and progression. Recent discoveries on the existence of tumor microbiota also in the TC microenvironment provide further evidence for the essential role of tumor microorganisms in TC etiology and severity, as well as acting as prognostic markers and as a potential target of adjuvant care in the treatment of TC patients. Therefore, in this review, we summarize current knowledge on the relationship of the tumor microbiome with the clinical tumor characteristics and TC progression, also illustrating the molecular mechanisms underlying this association, and how antioxidant nutrients may be used as a novel strategy to both control gut health and reduce the risk for TC. Furthermore, we discuss how new technologies might be exploited for the development of new foods with high nutritional values, antioxidant capability, and even attractiveness to the individual in terms of sensory and emotional features.

Thyroid hormone action during GABAergic neuron maturation: The quest for mechanisms

Thyroid hormone (TH) signaling plays a major role in mammalian brain development. Data obtained in the past years in animal models have pinpointed GABAergic neurons as a major target of TH signaling during development, which opens up new perspectives to further investigate the mechanisms by which TH affects brain development. The aim of the present review is to gather the available information about the involvement of TH in the maturation of GABAergic neurons. After giving an overview of the kinds of neurological disorders that may arise from disruption of TH signaling during brain development in humans, we will take a historical perspective to show how rodent models of hypothyroidism have gradually pointed to GABAergic neurons as a main target of TH signaling during brain development. The third part of this review underscores the challenges that are encountered when conducting gene expression studies to investigate the molecular mechanisms that are at play downstream of TH receptors during brain development. Unravelling the mechanisms of action of TH in the developing brain should help make progress in the prevention and treatment of several neurological disorders, including autism and epilepsy.

Autoantibodies to selenoprotein P in chronic fatigue syndrome suggest selenium transport impairment and acquired resistance to thyroid hormone

Chronic Fatigue Syndrome (CFS) presents with symptoms of hypothyroidism, including mental and physical fatigue, poor sleep, depression, and anxiety. However, thyroid hormone (TH) profiles of elevated thyrotropin and low thyroxine (T4) are not consistently observed. Recently, autoantibodies to the Se transporter SELENOP (SELENOP-aAb) have been identified in Hashimoto's thyroiditis and shown to impair selenoprotein expression. We hypothesized that SELENOP-aAb are prevalent in CFS, and associate with reduced selenoprotein expression and impaired TH deiodination. Se status and SELENOP-aAb prevalence was compared by combining European CFS patients (n = 167) and healthy controls (n = 545) from different sources. The biomarkers total Se, glutathione peroxidase (GPx3) and SELENOP showed linear correlations across the samples without reaching saturation, indicative of Se deficiency. SELENOP-aAb prevalence was 9.6-15.6% in CFS versus 0.9-2.0% in controls, depending on cut-off for positivity. The linear correlation between Se and GPx3 activity was absent in SELENOP-aAb positive patients, suggesting impaired Se supply of kidney. A subgroup of paired control (n = 119) and CSF (n = 111) patients had been characterized for TH and biochemical parameters before. Within this subgroup, SELENOP-aAb positive patients displayed particularly low deiodinase activity (SPINA-GD index), free T3 levels, total T3 to total T4 (TT3/TT4) and free T3 to free T4 (FT3/FT4) ratios. In 24 h urine, iodine concentrations were significantly lower in SELENOP-aAb positive than in SELENOP-aAb negative patients or controls (median (IQR); 43.2 (16.0) vs. 58.9 (45.2) vs. 89.0 (54.9) μg/L). The data indicate that SELENOP-aAb associate with low deiodination rate and reduced activation of TH to active T3. We conclude that a subset of CFS patients express SELENOP-aAb that disturb Se transport and reduce selenoprotein expression in target tissues. Hereby, TH activation decreases as an acquired condition not reflected by thyrotropin and T4 in blood. This hypothesis opens new diagnostic and therapeutic options for SELENOP-aAb positive CFS, but requires clinical evidence from intervention trials.

Unusual causes of hyperthyrotropinemia and differential diagnosis of primary hypothyroidism: a revised diagnostic flowchart

The clinical consequences of primary hypothyroidism include cardiovascular morbidity, increased mortality, and poor quality of life; therefore guidelines endorsed by several Scientific Societies recommend measuring circulating thyroid-stimulating hormone (TSH) in patients at risk. The assessment of serum TSH levels is also deemed to be the most robust and accurate biomarker during the management of replacement therapy in patients with a previous diagnosis of primary hypothyroidism. In line with a reflex TSH laboratory strategy, free thyroxine is measured only if the TSH falls outside specific cutoffs, in order to streamline investigations and save unjustified costs. This serum TSH-based approach to both diagnosis and monitoring has been widely accepted by several national and local health services; nevertheless, false-negative or -positive testing may occur, leading to inappropriate management or treatment. This review aims to describe several infrequent causes of increased circulating TSH, including analytical interferences, resistance to TSH, consumptive hypothyroidism, and refractoriness to levothyroxine replacement treatment. We propose a clinical flowchart to aid correct recognition of these various conditions, which represent important potential pitfalls in the diagnosis and treatment of primary hypothyroidism.

Influence of the TAS2R38 Gene Single Nucleotide Polymorphisms in Metabolism and Anthropometry in Thyroid Dysfunction

The gene TAS2R38 single nucleotide polymorphisms (SNPs-P49A, A262V and V296I) can condition bitter tasting by PAV (proline-alanine-valine) and non-bitter-tasting by AVI (alanine-valine-isoleucine) homozygosity. We evaluated this polymorphisms association with thyroid function, metabolism and anthropometry parameters determined by: Endpoint analysis (SNPs); DXA (fat mass-%, total fat mass-kg, lean mass-kg); Standard methods (lipid metabolism parameters, HbA1c-%, glycemia-mg/dL, insulinemia-µIU/mL, HOMA-IR, uricemia-mg/dL, calcemia-mg/dL and BMI-kg/m²); ELISA (leptinemia-ng/mL); Spectrophotometry (Angiotensin Converting Enzyme activity-UI/L). Statistics: SPSS program; OR [IC95%]; p < 0.05. Sample: 114 hypothyroid, 49 hyperthyroid, and 179 controls. An association between A262V-valine-valine and hypothyroidism/hyperthyroidism was verified (OR = 2.841; IC95% [1.726-4.676]), p < 0.001/OR = 8.915; IC95% [4.286-18.543]), p < 0.001). Protector effect from thyroid dysfunction: A262V-alanine-valine (OR = 0.467; IC95% [0.289-0.757], p = 0.002/OR = 0.132; IC95% [0.056-0.309], p < 0.001) and PAV (OR = 0.456; IC95% [0.282-0.737], p = 0.001/OR = 0.101; IC95% [0.041-0.250], p < 0.001). Higher parameter values associated with genotypes were: fat-mass-% (V296I-valine-isoleucine), lean-mass (P49A-proline-proline; PVI), leptin (AVI), HbA1c (A262V-alanine-valine) and lower values in lean-Mass (AVI; PVV), leptin (A262V-alanine-alanine), HbA1c (PVV), uricemia (V296I-valine-isoleucine), glycemia (A262V-alanine-alanine; AAV) and plasma triglycerides (PVV). In conclusion, TAS2R38 influences thyroid function, body composition and metabolism. Bitter taste perception (PAV) and the genotype A262V-alanine-valine can protect from thyroid dysfunction. AVV, PVV and genotype A262V-valine-valine may confer higher predisposition for thyroid dysfunction, particularly PVV for hyperthyroidism.

Severe consumptive hypothyroidism in hepatic hemangioendothelioma

OBJECTIVES

Consumptive hypothyroidism may occur in hepatic hemangioendothelioma. The altered expression of deiodinases inactivates peripheral thyroid hormones. As a result, serum levels of free triiodothyronine and free thyroxine are reduced to varying degrees. There are no established recommendations for the dosage of sirolimus for this particular indication. We describe for the first time the course of treatment with low-dose sirolimus.

CASE PRESENTATION

We present a 5-week-old infant with hepatic hemangioendothelioma and severe consumptive hypothyroidism. Due to hepatic infiltration he showed signs of right heart strain. Therapy of hemangioendothelioma was initiated with propranolol and, in the absence of response, methylprednisolone was added. Treatment was continued with low-dose sirolimus (due to side effects) and propranolol. Hypothyroidism was managed with levothyroxine and liothyronine.

CONCLUSIONS

Consumptive hypothyroidism due to cutaneous hemangioma and hepatic hemangioendothelioma can be managed with propranolol and low-dose sirolimus. Treatment of severe hypothyroidism may require a combinational therapy by substitution of both T3 and T4.

Consumptive Hypothyroidism due to Hepatic Hemangiomas: A Case Series and Review of the Literature

Consumptive hypothyroidism (CH) is a rare and potentially overlooked complication of hepatic hemangiomas (HH) overexpressing the enzyme deiodinase, which converts thyroxine (T4) to reverse triiodothyronine (rT3).

Materials and methods

Here, we report a case series of 3 patients and a systematic review of the literature.

Results

Hypothyroidism (mean serum TSH 52.03 mIU/L) was detected at a mean age of 4.6 months (range 3-6) in 3 infants with infantile hepatic hemangiomas, treated with thyroxine (mean dose 12 µg/kg/day). All received treatment with propranolol (1-3 mg/kg/day) from the mean age of 4 months. Hormonal treatment was stopped at a mean age of 20 months (range 12-30). Hypothyroidism reoccurred in a patient concurrently with the increase of liver lesions, requiring liver transplantation (LT) at age 39 months.Literature review retrieved 42 studies (48 patients): HH (n = 43) were isolated in 24 infants and associated with cutaneous hemangiomas in 19. Hemangiomas were only cutaneous in 5.In the first 43 patients, hypothyroidism was detected at a mean age of 1 month; 21 of 43 patients were prescribed propranolol alone (n = 8) or associated with other medicaments (n = 13); 2 of 43 patients underwent LT. Hormonal treatment consisted of T4 in 35 of 43 patients and T3 in 10.CH associated with only cutaneous and extrahepatic visceral hemangiomas (n = 5), detected at a mean age of 7 months (TSH mean levels at diagnosis of 150.3 mIU/L). Three of 5 patients received treatment with propranolol ± other medicaments. All 5 patients were treated with T4.

Conclusions

Periodical thyroid function assessment is necessary in patients with hepatic hemangiomas, particularly when lesions' size and number increase rapidly.

A decrease in peripheral thyroid hormone conversion efficiency in patients treated with immune checkpoint inhibitors and L-T3 as a possible alternative therapeutic escape option

Hypothyroidism is a frequently occurring side effect in patients under treatment with immune checkpoint inhibitors (ICIs). Actually, the origin of hypothyroidism with ICI use is classified as a primary (thyroid) or as secondary/tertiary hypothyroidism (hypothalamus-pituitary). Treatment consists of levothyroxine (L-T4) substitution. Recently, we were rarely confronted with a clinically overt hypothyroidism in three patients under treatment with ICIs who were non-responsive to T4 therapy. As a therapeutical escape, liothyronine (L-T3) was started with a significant clinical and/or biochemical improvement suggesting an underlying functional defect in the peripheral free T4 (fT4) to free T3 (fT3) conversion (as supported by calculation of SPINA-GD). Against this background, we discussed our three patients along an extended review of this clinical topic.

Effects of methylisothiazolinone and octylisothiazolinone on development and thyroid endocrine system in zebrafish larvae

Methylisothiazolinone (MIT) and octylisothiazolinone (OIT) are used as preservatives and biocides to prevent product decay or deterioration. In the present study, developmental toxicity and the effect on the thyroid endocrine system were investigated in zebrafish embryos exposed to MIT and OIT for 96 h. Coagulation was significantly increased when zebrafish embryos were exposed to a concentration of 300 μg/L MIT and ≥ 0.3 μg/L OIT, resulting in a significant decrease in hatchability and larvae survival. The body length in zebrafish larvae exposed to 30 μg/L OIT was significantly shorter than that of the control group. The whole-body levels of triiodothyronine and thyroxine were significantly decreased in larvae exposed to MIT and OIT. Significant upregulation of crh, trh, tshβ, and tshr genes and downregulation of trαa, tg, ttr, and deio2 genes were observed in fish exposed to two isothiazolinones. The expression of dre-miR-193b and dre-miR-499 was significantly increased in zebrafish larvae exposed to MIT and OIT, indicating that epigenetic deregulation of miRNAs modulated genes involved in thyroid hormone regulation. OIT has a higher magnitude of toxicity than MIT, corresponding to the observed changes in thyroid hormones and developmental toxicity.

Increased Thyroid-Hormone Requirements Consistent With Type 3 Deiodinase Induction Related to Ibrutinib in a Thyroidectomized Woman

Objective

Tyrosine-kinase inhibitors (TKIs) are chemotherapeutic agents associated with increased thyroid-hormone requirements and altered deiodinase activity. We present the first case to link these findings to the TKI ibrutinib.

Methods

Serial thyroid-stimulating hormone (TSH), free-thyroxine (FT4), free-triiodothyronine (FT3), and reverse-triiodothyronine (rT3) levels were assessed.

Results

An 80-year-old, 62-kg woman with hypothyroidism secondary to total thyroidectomy for stage I papillary thyroid cancer, on maintenance levothyroxine (LT4) 137 μg daily, presented for follow-up. Compared to one year prior, the patient’s weight had increased by 2 kg and TSH from 2.58 to 27.60 μIU/mL (normal: 0.45-4.50 μIU/mL) while on pantoprazole. Ibrutinib, her other medication, had been started seven months prior for chronic lymphocytic leukemia. Despite sequential confirmation of proper LT4 adherence and self-administration, adjustment of LT4 to 150 μg, and discontinuation of pantoprazole, the patient’s hypothyroid symptoms worsened, and the TSH was 73.90 μIU/mL six months later. LT4 was increased to 175 μg six days a week and 262.5 μg once weekly. Two months later, the TSH was 3.92 μIU/mL (steady-state condition), FT4 2.32 ng/dL (normal: 0.82-1.77 ng/dL), FT3 1.6 pg/mL (normal: 2.0-4.4 pg/mL), and rT3 69.6 ng/dL (normal: 9.2-24.1 ng/dL). Ibrutinib was discontinued the next month due to gastrointestinal side effects and elevated blood pressure. Four months later, LT4 had been reduced to 150 μg, and the FT4 reached 1.92 ng/dL, FT3 2.0 pg/mL, and rT3 26.6 ng/dL.

Conclusion

This report links ibrutinib to increased thyroid-hormone requirements in a thyroidectomized woman whose decreased T3:T4, T3:rT3, and T4:rT3 ratios suggested type 3 deiodinase induction and type 2 deiodinase inhibition.

Severe hyperthyroidism without symptoms due to nonthyroidal illness in a child with acute hepatitis: case report and literature review

While liver enzyme changes are frequently reported in hyperthyroidism, liver dysfunction itself can lead to alterations in thyroid hormone metabolism. However, the exact relationship between hyperthyroidism and liver dysfunction is unclear. We report an 11-year-old boy presenting with acute hepatitis of unknown etiology, who was incidentally found to have asymptomatic biochemical hyperthyroidism. Despite significant total and free T4 elevation, clinical evidence of thyrotoxicosis was absent. Thyroid I-123 uptake was also reduced. Additional testing revealed slight T3 elevation and significant rT3 elevation. Graves' and Hashimoto's thyroiditis testing was negative. We hypothesize that the biochemical hyperthyroidism was due to transient thyroiditis. Although an etiology for the boy's hepatitis was never determined, and an undiagnosed infectious etiology causing subacute thyroiditis was considered, subsequent testing showing positive thyroid peroxidase antibodies, suggesting autoimmune Hashimoto's thyroiditis as the likely cause of the hyperthyroidism. We believe, furthermore, that the absence of symptoms was the result of concurrent nonthyroidal illness resulting in the biochemical findings of slight T3 elevation and significant rT3 increase despite significant T4 elevation.

Update of hypothyroidism and its management in Unani medicine

Hypothyroidism is a clinical syndrome caused by thyroid hormone deficiency due to reduced production, deranged distribution, or lack of effects of thyroid hormone. The prevalence of hypothyroidism in developed countries is around 4-5%, whereas it is about 11% in India, only 2% in the UK, and 4·6% in the USA. It is more common in women than in men. Hypothyroidism has multiple etiologies and manifestations. The most common clinical manifestations are weight gain, loss of hair, cold intolerance, lethargy, constipation, dry skin, and change in voice. The signs and symptoms of hypothyroidism differ with age, gender, severity of condition, and some other factors. The diagnosis is based on clinical history, physical examination and serum level of FT3, FT4, and thyroid-stimulating hormone, imaging studies, procedures, and histological findings. The treatment of choice for hypothyroidism is levothyroxine, however; in this review article, we have discussed the epidemiology, etiology, clinical sign and symptoms, diagnosis, complications, and management of hypothyroidism in modern medicine and a comparative treatment by the Unani system of medicine (USM). In the USM, the main emphasis of the principle of treatment (Usool-e-Ilaj) is to correct the abnormal constitution (Su-e-Mizaj) and alter the six prerequisites for existence (Asbab-e-Sitta Zarooriya) to restore normal health. It is a packaged treatment, that is, different components of treatment are given as a package form which includes different drugs, dosages form, and regimens.

A Case of Consumptive Hypothyroidism in a 1-Month-Old Boy with Diffuse Infantile Hepatic Hemangiomas

Consumptive hypothyroidism is a rare paraneoplastic syndrome characterized by excessive inactivation of the thyroid hormones due to increased type 3 iodothyronine deiodinase activity of tumors. We report the case of severe consumptive hypothyroidism in a 1-month-old boy with infantile hepatic hemangiomas who presented with cardiac failure and cholestasis. Diffuse infiltration of hepatic hemangiomas was detected on abdominal imaging studies, and thyroid function screening test revealed severe hypothyroidism, which necessitated the administration of higher-than-usual doses of levothyroxine for the normalization of thyroid function. The patient was successfully treated with propranolol, prednisolone, and levothyroxine, and he showed normal thyroid function at 3 months of age and normal neurodevelopment at 9 months of age. This case highlights the importance of early recognition and prompt management of consumptive hypothyroidism in patients with infantile hepatic hemangiomas.

Follow-up of infants with congenital hypothyroidism and low total thyroxine/thyroid stimulating hormone on newborn screen

PURPOSE

Newborn screening (NBS) methods to detect congenital hypothyroidism (CH) vary regarding whether total thyroxine (T4), thyroid stimulating hormone (TSH), or both are measured. Neonates with low T4 and normal or low TSH (lowT4/TSH) may only be detected by T4-inclusive methods or age-dependent repeat screens. Premature neonates and those with pituitary-hypothalamic disorders frequently manifest lowT4/TSH.

METHODS

This is a retrospective case-study of newborns who were screen-positive for lowT4/TSH in Alabama in 2009-2016 using a combined T4 and TSH method and 2 routine NBS. The clinical, laboratory, and final diagnosis after 3 years were determined.

RESULTS

Over 8 years, 225 infants were referred to our institution for evaluation and treatment of CH. Twelve infants were screen-positive for lowT4/TSH by first or second NBS. Four of the 12 infants had permanent CH (30%): 2 with primary and 2 with central etiologies. One infant with moderately severe central CH was only detected by the routine second NBS. Six of 7 premature infants had elevated TSH on serum confirmation labs consistent with a delay in hypothalamic-pituitary maturation, yet 2 of these patients were later established to have permanent primary CH. While most cases of lowT4/TSH resolved by 3 years of age, several neonates had extended periods of moderate to severe hypothyroxinemia prior to detection and treatment.

CONCLUSION

One third of the infants with lowT4/TSH on NBS in this study had permanent CH. These results emphasize the importance of T4-based assay methods, subsequent (repeat) screens and long-term follow-up in the management of neonates with lowT4/TSH on newborn screen.

Combination therapy of propranolol, levothyroxine, and liothyronine was effective in a case of severe consumptive hypothyroidism associated with infantile hepatic hemangioma

Infantile hepatic hemangioma (IHH) can be accompanied by consumptive hypothyroidism. We report the case of a 4-mo-old boy who showed massive hepatomegaly, peripheral coldness, lethargy, and failure to thrive. An enhanced computed tomography scans demonstrated multiple hemangiomas in both lobes of the liver, and a thyroid function tests showed severe hypothyroidism: TSH 561.5 µIU/mL, free triiodothyronine (fT₃) 1.0 pg/mL, and free thyroxine (fT₄) < 0.7 ng/dL. IHH gradually regressed following propranolol treatment and fT₄ increased to a low normal level (1.0 ng/dL) by high dose replacement of levothyroxine, while fT₃ remained very low (< 1.0 pg/mL), even following high doses of levothyroxine; fT₃ eventually normalized following the administration of liothyronine. We suggest that treatment strategies should be individualized based on thyroid function, and that the combination therapy of propranolol for anti-tumor treatment and levothyroxine and liothyronine for respective thyroid hormone replacement is effective, particularly in cases of severe consumptive hypothyroidism due to multiple IHHs.

Iodine and Myo-Inositol: A Novel Promising Combination for Iodine Deficiency

Despite universal salt iodization programmes implemented over the last decades, iodine deficiency remains a major public health problem in many countries worldwide. Endeavors are still required to ensure sufficient iodine intake in the populations at risk in order to eliminate deficiency. Iodine is crucial for the synthesis of thyroid hormones triiodothyronine (T₃) and thyroxine (T₄), as well as for the thyroid health. When iodine levels are insufficient, T₄ attests toward the lower limit of the physiological range, causing subtle fluctuations in the T₃:T₄ ratio. Monitoring these variations may be an accurate way to assess patient's iodine status. Recently, a number of published clinical studies documented a growing interest toward the use of myo-inositol in thyroid diseases. Myo-inositol, a carbocyclic polyol, regulates the generation of hydrogen peroxide (H₂O₂) in thyrocytes, crucial for iodine organification and thyroid hormone biosynthesis. Thus, combined supplementation of iodine and myo-inositol may promote higher iodine availability in thyrocytes improving thyroid functionality. This review presents novel strategies for the diagnosis and the management of iodine deficiency, focusing on the potential role of myo-inositol combined with iodine.

Recurrent bloody stools associated with visceral infantile haemangioma in a preterm twin girl

A premature twin infant girl was transferred to a level IV neonatal intensive care unit for recurrent bloody stools, anaemia and discomfort with feeds; without radiographic evidence of necrotising enterocolitis. Additional imaging after transfer revealed a large retroperitoneal mass in the region of the pancreas compressing the inferior vena cava and abdominal aorta, raising suspicion for neuroblastoma. Abdominal exploration and biopsy unexpectedly revealed that the lesion was an infantile capillary haemangioma involving the small bowel, omentum, mesentery and pancreas. The infant was subsequently treated with propranolol, with a decrease in the size of the lesion over the first year of her life and a drastic improvement in feeding tolerance. While cutaneous infantile haemangiomas are common, visceral infantile haemangiomas are less so and may present a significant diagnostic challenge for clinicians. This interesting case demonstrates that such lesions should be considered in the differential diagnosis for unexplained gastrointestinal bleeding or abdominal symptoms in newborns.

Post-myocardial infarction exercise training beneficially regulates thyroid hormone receptor isoforms

Thyroid hormone receptors (TRs) play a critical role in the expression of genes that are major determinants of myocardial contractility, including α-myosin heavy chain (α-MHC) and β-MHC. After myocardial infarction (MI), changes in myocardial TRs consistently correlate with changes in thyroid hormone (TH) target gene transcription, and this is thought to play a key role in the progression to end-stage heart failure. Interestingly, post-MI exercise training has been shown to beneficially alter TH-target gene transcription and preserve cardiac function without changing serum TH. Therefore, in this study, we investigated whether mild exercise training alters expression of α1 and β1 TR isoforms in post-MI rats. Seven-week-old male Sprague-Dawley rats underwent coronary ligation or sham operation, and were assigned to 3 groups (n = 10): sham, sedentary MI (MI-Sed), and exercise MI (MI-Ex). Treadmill training was initiated 1 week post-MI, and gradually increased up to 16 m/min, 5° incline, 50 min/day, 5 days/week, and lasted for a total of 8 weeks. Real-time polymerase chain reaction and gel electrophoresis were performed to quantify changes in TR isoforms. Our results illustrated that mRNA expression of TR-α1 and TR-β1 was higher in both MIs; however, protein electrophoresis data showed that TR-α1 was 1.91-fold higher (P < 0.05) and TR-β1 was 1.62-fold higher (P < 0.05) in the MI-Ex group than in the MI-Sed group. After MI, TR-α1 and TR-β1 protein levels are significantly decreased in the surviving non-infarcted myocardium. Moderate-intensity exercise training significantly increases TR-α1 and TR-β1 protein expression, which in turn may upregulate α-MHC and improve myocardial contractile function and prognosis.

Van Wyk-Grumbach syndrome with hemangioma in an infant

Background Van Wyk-Grumbach syndrome (VWGS) is characterized by juvenile primary hypothyroidism, delayed bone age and isosexual incomplete precocious puberty with reversal to the prepubertal state following thyroid hormone replacement. Case presentation In this case, an 18-month-old girl presented with premature menarche since 9 months of age, delayed bone age and enlarged bilateral multicystic ovaries along with a superficial infantile hemangioma over the upper anterior chest. VWGS was diagnosed based on the clinical features. High serum thyroid stimulating hormone and low free thyroxine with the absence of any carpal bones in the wrist X-ray were suggestive of congenital hypothyroidism. Interestingly, the coexisting hemangioma could also play a role in the etiology of the hypothyroidism through "consumptive hypothyroidism". Thyroid hormone replacement resulted in the complete resolution of signs and symptoms. Conclusions Untreated congenital hypothyroidism of short duration, onset of symptoms in infancy and association of an infantile hemangioma in VWGS were the unique features in our case.

Severe consumptive hypothyroidism caused by multiple infantile hepatic haemangiomas

Background Infantile hepatic haemangiomas (IHHs) produce an excess of the thyroid hormone inactivating enzyme type-3 iodothyronine deiodinase (D3), leading to rapid degradation of thyroid hormones and consumptive hypothyroidism. The L-thyroxine replacement dose in patients with consumptive hypothyroidism is inappropriately higher than that in congenital hypothyroidism. Case presentation A 4-month-old boy presented with abdominal distention. Thyroid function tests (TFTs) revealed an elevated thyroid-stimulating hormone (TSH) level of 177 mU/L, normal free thyroxine (fT4) of 1.23 ng/dL, low free tri-iodothyronine (fT3) of 1.55 pg/mL and increased reverse T3 (rT3) of 1240 ng/dL. Abdominal ultrasound and magnetic resonance imaging (MRI) revealed multiple IHHs. Based on his TFTs, ultrasonography and MRI evidence, he was diagnosed with consumptive hypothyroidism, and L-thyroxine replacement at 15 μg/kg/day was started. The L-thyroxine dose was increased gradually to 35 μ/kg/day until a stabilising euthyroid status was achieved. By the age of 8 months, the TSH concentration was decreased to normal levels; the L-thyroxine dose was gradually reduced and finally discontinued at the age of 12 months. Repeat abdominal ultrasound and MRI revealed a reduction in the number and size of the haemangiomas. The TFTs were at normal reference levels. The patient remains in active follow-up. Conclusions Neonatal screening for congenital hypothyroidism is usually negative in cases of IHH, as seen in our case. A high index of suspicion is necessary to diagnose hypothyroidism in cases of IHH. The present case required very high doses of levothyroxine to achieve a euthyroid status. In cases of hypothyroidism in the first year of life with consumptive hypothyroidism caused by hepatic haemangioma, aggressive L-thyroxine replacement is required with no upper limit. The dose should be increased gradually until a stabilising euthyroid status is achieved.

Subclinical Changes in Maternal Thyroid Function Parameters in Pregnancy and Fetal Growth

CONTEXT

Overt thyroid disease in pregnancy is a known risk factor for abnormal fetal growth and development. Data on the effects of milder forms of variation in maternal thyroid function on intrauterine growth are less well examined.

OBJECTIVE

We explored these associations using repeated thyroid hormone and ultrasound measurements.

DESIGN, SETTING, AND PARTICIPANTS

Data were obtained from 439 pregnant women without diagnosed thyroid disease who were participants in a case-control study of preterm birth nested within an ongoing prospective birth cohort in Boston, Massachusetts.

MAIN OUTCOME MEASURES

Ultrasound and delivery indices of fetal growth were standardized to those measured in a larger population.

RESULTS

At median 10, 18, and 26 weeks of gestation, we observed significant inverse associations between free thyroxine (FT4) and birth weight z scores, with the strongest association detected at median 10 weeks, at which time a 10% increase in FT4 was associated with a 0.02 z score decrease (∼8.5 g) in birth weight (β = -0.41 for ln-transformed FT4; 95% confidence interval, -0.64 to -0.18). FT4 was also inversely associated with repeated measurements of estimated fetal weight, head circumference, and abdominal circumference. We observed weaker inverse associations for total T4 and a positive relationship between total triiodothyronine and birth weight z scores. We did not observe any associations for thyroid-stimulating hormone.

CONCLUSION

In pregnant women without overt thyroid disease, subclinical changes in thyroid function parameters may influence fetal growth.

The classic pathways of thyroid hormone metabolism

Thyroid hormones (TH) are crucial for growth and development and play an important role in energy homeostasis. Although serum TH levels are relatively constant in the physiological state, TH bioavailability at the tissue and cellular level is dependent on local TH metabolism. Circulating TH produced by the thyroid can be metabolized by a number of different pathways resulting in 1) activation of TH 2) deactivation of TH or 3) excretion of TH and subsequent metabolites. These pathways play an essential role in determining local TH levels and action. The major classical pathways of TH metabolism are deiodination, sulfation, glucuronidation, and ether-link cleavage. This review provides an overview of these pathways, their relative contributions to TH levels in the serum and in various organs and the changes in these pathways elicited by fasting and illness.

Role of thyroid hormones in the neoplastic process: an overview

Thyroid hormones (TH) are critical regulators of several physiological processes, which include development, differentiation and growth in virtually all tissues. In past decades, several studies have shown that changes in TH levels caused by thyroid dysfunction, disruption of deiodinases and/or thyroid hormone receptor (TR) expression in tumor cells, influence cell proliferation, differentiation, survival and invasion in a variety of neoplasms in a cell type-specific manner. The function of THs and TRs in neoplastic cell proliferation involves complex mechanisms that seem to be cell specific, exerting effects via genomic and nongenomic pathways, repressing or stimulating transcription factors, influencing angiogenesis and promoting invasiveness. Taken together, these observations indicate an important role of TH status in the pathogenesis and/or development of human neoplasia. Here, we aim to present an updated and comprehensive picture of the accumulated knowledge and the current understanding of the potential role of TH status on the different hallmarks of the neoplastic process.

Use of liothyronine without levothyroxine in the treatment of mild consumptive hypothyroidism caused by hepatic hemangiomas

There have been reports of the use of levothyroxine or levothyroxine plus liothyronine for consumptive hypothyroidism caused by hepatic hemangiomas. Administration of levothyroxine without liothyronine can be inadequate to maintain normal levels of both free T3 and free T4 in some patients. However, there is no report of treatment with liothyronine plus propranolol. We herein present a case in which we used liothyronine therapy for multifocal hepatic hemangiomas in a Japanese patient with low free T3 and normal free T4 levels. A 2-month-old Japanese male was referred to our hospital because of jaundice. Abdominal computed tomography showed multifocal hemangiomas in both lobes of the liver. TSH level was elevated, free T3 level was low, free T4 level was normal, and hypothyroidism due to hepatic hemangiomas was diagnosed. In addition to propranolol, liothyronine was started. We used liothyronine without levothyroxine for hypothyroidism because only free T3 level had decreased, whereas free T4 level remained in the normal range. The TSH and free T3 levels normalized in this patient in less than 1 month. The liothyronine dose was gradually reduced with regression of the hemangiomas, and liothyronine administration was discontinued at the age of 5 months. At the age of 11 months, growth and neurological development of the patient met age-specific norms, and he was euthyroid at that time. This is the first report demonstrating the use of liothyronine with propranolol for treatment of this type of consumptive hypothyroidism.

Diffuse hepatic hemangioma with single cutaneous hemangioma: an alerting occurrence

Screening of infants with five or more cutaneous infantile hemangiomas with abdominal ultrasound is often recommended. However, diffuse hepatic hemangioma can develop even in patients with single cutaneous hemangioma. This highlights the importance of physical examination and screening ultrasound in these patients.

Thyroid Allostasis-Adaptive Responses of Thyrotropic Feedback Control to Conditions of Strain, Stress, and Developmental Programming

The hypothalamus-pituitary-thyroid feedback control is a dynamic, adaptive system. In situations of illness and deprivation of energy representing type 1 allostasis, the stress response operates to alter both its set point and peripheral transfer parameters. In contrast, type 2 allostatic load, typically effective in psychosocial stress, pregnancy, metabolic syndrome, and adaptation to cold, produces a nearly opposite phenotype of predictive plasticity. The non-thyroidal illness syndrome (NTIS) or thyroid allostasis in critical illness, tumors, uremia, and starvation (TACITUS), commonly observed in hospitalized patients, displays a historically well-studied pattern of allostatic thyroid response. This is characterized by decreased total and free thyroid hormone concentrations and varying levels of thyroid-stimulating hormone (TSH) ranging from decreased (in severe cases) to normal or even elevated (mainly in the recovery phase) TSH concentrations. An acute versus chronic stage (wasting syndrome) of TACITUS can be discerned. The two types differ in molecular mechanisms and prognosis. The acute adaptation of thyroid hormone metabolism to critical illness may prove beneficial to the organism, whereas the far more complex molecular alterations associated with chronic illness frequently lead to allostatic overload. The latter is associated with poor outcome, independently of the underlying disease. Adaptive responses of thyroid homeostasis extend to alterations in thyroid hormone concentrations during fetal life, periods of weight gain or loss, thermoregulation, physical exercise, and psychiatric diseases. The various forms of thyroid allostasis pose serious problems in differential diagnosis of thyroid disease. This review article provides an overview of physiological mechanisms as well as major diagnostic and therapeutic implications of thyroid allostasis under a variety of developmental and straining conditions.

An Improved Nonradioactive Screening Method Identifies Genistein and Xanthohumol as Potent Inhibitors of Iodothyronine Deiodinases

BACKGROUND

Deiodinases (DIO1, 2, and 3) are key enzymes in thyroid hormone (TH) activation and inactivation with impact on energy metabolism, development, cell differentiation, and a number of other physiological processes. The three DIO isoenzymes thus constitute sensitive rate-limiting components within the TH axis, prone to dysregulation by endocrine disruptive compounds or disease state. In animal models and cell culture experiments, they serve as readout for local TH status and disarrangement of the hormonal axis. Furthermore, some human diseases are characterized by apparent deiodinase dysregulation (e.g., the low triiodothyronine syndrome in critical illness). Consequently, these enzymes are targets of interest for the development of pharmacological compounds with modulatory activities. Until now, the portfolio of inhibitors for these enzymes is limited. In the clinics, the DIO1-specific inhibitor propylthiouracil is in use for treatment of severe hyperthyroidism. Other well-known inhibitors (e.g., iopanoic acid or aurothioglucose) are nonselective and block all three isoenzymes. Furthermore, DIO3 was shown to be a potential oncogenic gene, which is strongly expressed in some tumors and might, in consequence, protect tumor tissue form differentiation by TH. With respect to its role in tumorigenesis, specific inhibitors of DIO3 as a potential target for anticancer drugs would be highly desirable. To this end, a flexible and convenient assay for high-throughput screening is needed. We recently described a nonradioactive screening assay, utilizing the classic Sandell-Kolthoff reaction as readout for iodide release from the substrate molecules. While we used murine liver as enzyme source, the assay was limited to murine DIO1 activity testing. Here, we describe the use of recombinant proteins as enzyme sources within the assay, expanding its suitability from murine Dio1 to human DIO1, DIO2, and DIO3.

METHODS

As proof-of-concept, deiodination reactions catalyzed by these recombinant enzymes were monitored with various nonradioactive substrates and confirmed by liquid chromatography-tandem mass spectrometry.

RESULTS

The contrast agent and known DIO inhibitor iopanoic acid was characterized as readily accepted substrate by DIO2 and Dio3. In a screening approach using established endocrine disrupting compounds, the natural food ingredient genistein was identified as a further DIO1-specific inhibitor, while xanthohumol turned out to potently block the activity of all three isoenzymes.

CONCLUSIONS

A rapid nonradioactive screening method based on the Sandell-Kolthoff reaction is suitable for identification of environmental, nutritive and pharmacological compounds modulating activities of human deiodinase enzymes.

Genetic determination of the hypothalamic-pituitary-thyroid axis: where do we stand?

For a long time it has been known that both hypo- and hyperthyroidism are associated with an increased risk of morbidity and mortality. In recent years, it has also become clear that minor variations in thyroid function, including subclinical dysfunction and variation in thyroid function within the reference range, can have important effects on clinical endpoints, such as bone mineral density, depression, metabolic syndrome, and cardiovascular mortality. Serum thyroid parameters show substantial interindividual variability, whereas the intraindividual variability lies within a narrow range. This suggests that every individual has a unique hypothalamus-pituitary-thyroid axis setpoint that is mainly determined by genetic factors, and this heritability has been estimated to be 40-60%. Various mutations in thyroid hormone pathway genes have been identified in persons with thyroid dysfunction or altered thyroid function tests. Because these causes are rare, many candidate gene and linkage studies have been performed over the years to identify more common variants (polymorphisms) associated with thyroid (dys)function, but only a limited number of consistent associations have been found. However, in the past 5 years, advances in genetic research have led to the identification of a large number of new candidate genes. In this review, we provide an overview of the current knowledge about the polygenic basis of thyroid (dys)function. This includes new candidate genes identified by genome-wide approaches, what insights these genes provide into the genetic basis of thyroid (dys)function, and which new techniques will help to further decipher the genetic basis of thyroid (dys)function in the near future.