Consumptive hypothyroidism resulting from hepatic vascular tumors in an athyreotic adult

Thyroid hormone economy in mice overexpressing iodothyronine deiodinases

In peripheral tissues, triiodothyronine (T3) production and consequent thyroid hormone actions are mainly regulated by iodothyronine deiodinases (DIOs) classified into 3 types: D1, D2, and D3. We aimed to investigate the effects of peripheral DIOs on thyroid hormone economy independent of the hypothalamus-pituitary-thyroid axis. We cloned coding sequences of human DIOs with FLAG-tag and HiBiT-tag sequences into a pcDNA3.1 vector. To obtain full-length proteins, we modified these vectors by cloning the selenocysteine insertion sequence of each DIO (SECIS vectors). Western blot analyses and HiBiT lytic assay using HEK293T cells revealed that SECIS vectors expressed full-length proteins with substantial activity. Subsequently, in vivo transfections of pLIVE-based SECIS vectors into male C57BL/6J mice were performed by hydrodynamic gene delivery to generate mice overexpressing DIOs predominantly in the liver (D1, D2, and D3 mice). After 7 days from transfections, mice were analyzed to clarify phenotypes. To summarize, serum thyroid hormone levels did not change in D1 mice but D2 mice had higher serum free T3 levels. D3 mice developed hypothyroidism with higher serum reverse T3 (rT3) levels. Transfections with levothyroxine administration suggested that thyroid hormone action was upregulated in D2 mice. Our DIO-overexpressing mice provided insights on the physiological properties of upregulated DIOs: D2 augments local thyroid hormone action and recruits T3 into the circulation: D3 decreases circulating T3 and T4 levels with elevated rT3, leading to consumptive hypothyroidism. As D3 mice are expected to be a novel hypothyroidism model, they can contribute to progress in the field of thyroid hormone economy and action.

Paradigms of Dynamic Control of Thyroid Hormone Signaling

Thyroid hormone (TH) molecules enter cells via membrane transporters and, depending on the cell type, can be activated (i.e., T4 to T3 conversion) or inactivated (i.e., T3 to 3,3'-diiodo-l-thyronine or T4 to reverse T3 conversion). These reactions are catalyzed by the deiodinases. The biologically active hormone, T3, eventually binds to intracellular TH receptors (TRs), TRα and TRβ, and initiate TH signaling, that is, regulation of target genes and other metabolic pathways. At least three families of transmembrane transporters, MCT, OATP, and LAT, facilitate the entry of TH into cells, which follow the gradient of free hormone between the extracellular fluid and the cytoplasm. Inactivation or marked downregulation of TH transporters can dampen TH signaling. At the same time, dynamic modifications in the expression or activity of TRs and transcriptional coregulators can affect positively or negatively the intensity of TH signaling. However, the deiodinases are the element that provides greatest amplitude in dynamic control of TH signaling. Cells that express the activating deiodinase DIO2 can rapidly enhance TH signaling due to intracellular buildup of T3. In contrast, TH signaling is dampened in cells that express the inactivating deiodinase DIO3. This explains how THs can regulate pathways in development, metabolism, and growth, despite rather stable levels in the circulation. As a consequence, TH signaling is unique for each cell (tissue or organ), depending on circulating TH levels and on the exclusive blend of transporters, deiodinases, and TRs present in each cell. In this review we explore the key mechanisms underlying customization of TH signaling during development, in health and in disease states.

Thyroid hormone availability in the human fetal brain: novel entry pathways and role of radial glia

Thyroid hormones (TH) are crucial for brain development; their deficiency during neurodevelopment impairs neural cell differentiation and causes irreversible neurological alterations. Understanding TH action, and in particular the mechanisms regulating TH availability in the prenatal human brain is essential to design therapeutic strategies for neurological diseases due to impaired TH signaling during neurodevelopment. We aimed at the identification of cells involved in the regulation of TH availability in the human brain at fetal stages. To this end, we studied the distribution of the TH transporters monocarboxylate transporter 8 (MCT8) and organic anion-transporting polypeptide 1C1 (OATP1C1), as well as the TH-metabolizing enzymes types 2 and 3 deiodinases (DIO2 and DIO3). Paraffin-embedded human brain sections obtained from necropsies of thirteen fetuses from 14 to 38 gestational weeks were analyzed by immunohistochemistry and in situ hybridization. We found these proteins localized along radial glial cells, in brain barriers, in Cajal-Retzius cells, in migrating fibers of the brainstem and in some neurons and glial cells with particular and complex spatiotemporal patterns. Our findings point to an important role of radial glia in controlling TH delivery and metabolism and suggest two additional novel pathways for TH availability in the prenatal human brain: the outer, and the inner cerebrospinal fluid-brain barriers. Based on our data we propose a model of TH availability for neural cells in the human prenatal brain in which several cell types have the ability to autonomously control the required TH content.

Consumptive Hypothyroidism: Case Report of Hepatic Hemangioendotheliomas Successfully Treated with Vincristine and Systematic Review of the Syndrome

OBJECTIVES

To provide a comprehensive description of consumptive hypothyroidism syndrome (CHS), a severe form of hypothyroidism that occurs due to the high expression levels of thyroid hormone inactivation enzyme type 3 deiodinase (D3) in tumors.

STUDY DESIGN

Case report and systematic review.

RESULTS

A 7-month-old girl with a diagnosis of massive hepatic hemangioendotheliomas was treated with high doses of thyroid hormones and tumor-directed chemotherapy with vincristine. The tumor displayed excellent response, and euthyroid status was regained. A systematic review on the databases PubMed/Medline and Embase was performed, using the term "Consumptive AND "Hypothyroidism." From the 33 selected references, we extracted 42 case reports of CHS: 36 children and 6 adults. The laboratory profile at diagnosis displayed high TSH and low T4 and T3 serum levels. The serum reverse T3 and D3 activity levels were high in all patients tested. In children, 97% had vascular tumors, whereas in adults 33% were vascular tumors, 33% fibrous tumors, and 33% gastrointestinal stromal tumors. The conservative treatment was predominant in children, while in adults all cases were treated with surgery. Death occurred in 16% of children and 33% of adults.

CONCLUSIONS

CHS is a rare form of hypothyroidism that occurs in children and adults, usually linked to hepatic vascular tumors. The condition is associated with high lethality. Prompt diagnosis, followed by high-dose thyroid hormone replacement and tumor-directed therapy are the keys to optimize outcomes.

Consumptive hypothyroidism due to a gastrointestinal stromal tumor expressing type 3 iodothyronine deiodinase

CONTEXT

Gastrointestinal stromal tumors (GISTs) are responsive to sunitinib (the tyrosine kinase inhibitor), this agent is widely used in prevention relapse of GISTs and neo-adjuvant chemotherapy in GIST patients without operation opportunity. The use of these agents has both advantages and disadvantages. On the one hand, it can improve the outcome for patient. On the other hand, it may lead to consumptive hypothyroidism, a rare syndrome caused by increased catabolism of T4 and T3 by increased type 3 iodothyronine deiodinase (D3) activity. D3 is the major physiologic inactivator of thyroid hormone, this selenoenzyme catalyzes the inner-ring deiodination of T(4) to reverse T(3) and T(3) to 3, 3;-diiodothyronine, both of which are biologically inactive [1]. Increased monitoring and supernormal thyroid hormone supplementation are required for affected patient.

OBJECTIVE

The aim of the study was to report the first case of consumptive hypothyroidism in an athyreotic patient after surgical resection of gastrointestinal stromal tumor.

DESIGN, SETTING, AND PATIENT

A 60-year-old athyreotic male was presented and he was euthyroid when receiving a stable therapeutic dose of thyroid hormone which was used to treat consumptive hypothyroidism resulting from the side effects of sunitinib, which is used for treatment of neo-adjuvant chemotherapy in gastrointestinal stromal tumor. With a discovery of large D3-expressing gastrointestinal stromal tumor, this patient suffered from marked Hyperthyrotropinemia, which instantly worsened after surgical resection of the gastrointestinal stromal tumor and then continued for 12 weeks after the surgical resection, in spite of further increases in levothyroxine therapy. The patient also had low serum T3 and elevated serum reverse T3 (rT3).

INTERVENTION

The patient's consumptive hypothyroidism caused by marked overexpression of the thyroid hormone-inactivating D3 within the gastrointestinal stromal tumor and adjacent normal gastrointestinal tissue.

MAIN OUTCOME MEASURES AND RESULTS

D3 immunostaining of the patient's gastrointestinal stromal tumor was positive, with no significant immunoreactivity in adjacent normal gastrointestinal tissue. The expression levels of CD34, CD117, and DOG1 in peri-tumor tissue samples was lower than that in tumor tissue. The mRNA expression level of KIT exon17 in peri-tumor tissue was higher than that in tumor tissue.

CONCLUSIONS

This is the first case report of consumptive hypothyroidism in an adult after surgical partial resection of the gastrointestinal stromal tumor. This case demonstrates that hyperthyrotropinemia may worsen after surgical resection of the gastrointestinal stromal tumor.

Dyshormonogenesis seems to be more frequent in a group of Cameroonian children with congenital hypothyroidism

Congenital hypothyroidism is a main congenital endocrine disorder, affecting 1 in 4000 births. It is not well described in sub-Saharan countries, and to draw attention to that issue, we decided to describe affected pediatric patients. We retrospectively analyzed the records of eight patients over a period of 6 years. We analyzed clinical sings of hypothyroidism and psychomotor development; hormonal assays and thyroid ultrasound were performed. We included four boys and four girls aged from 3 to 84 months at diagnosis with a median thyroid-stimulating hormone (TSH) level of 156.5 mUI/L. All except one present with a moderate psychomotor delay. Other clinical signs were classical for hypothyroidism. Thyroid ultrasound performed showed a goiter in half of patients, a normal gland in three of them and a hypoplasic gland in the last one, consonant with dyshormonogenesis. We therefore concluded that dyshormonogenesis seems to be more frequent in our context, and this raised the issue of neonatal screening of hypothyroidism in Africa.

Vincristine for successful treatment of steroid-dependent infantile hemangiomas

Infantile hemangiomas (IHs) are common, although systemic therapy has been generally limited to circumstances of potential compromise of vital functions (airway, vision, feeding, or cardiac), risk of disfigurement, or bleeding. IHs have previously been shown to express high levels of type III deiodinase, which catabolizes active thyroid hormone, resulting in a state of severe hypothyroidism, termed "consumptive hypothyroidism." We describe an infant with diffuse hepatic hemangiomas who developed consumptive hypothyroidism who was initially treated successfully with systemic glucocorticoids and β-blockers. Several efforts to wean her medications were unsuccessful. She subsequently developed severe growth restriction and treatment alternatives were sought. Although previously limited to treatment of life-threatening hemangiomas, a trial of vincristine was initiated. She was ultimately weaned from all systemic therapies, with recovery of a normal growth trajectory. This case highlights broader indications for vincristine as a safe and effective systemic therapy for treatment of IHs. It also stresses the importance of close anthropometric monitoring of infants and toddlers receiving glucocorticoid therapy and intervention when growth compromise becomes evident.

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.

Guidelines for the treatment of hypothyroidism: prepared by the american thyroid association task force on thyroid hormone replacement

BACKGROUND

A number of recent advances in our understanding of thyroid physiology may shed light on why some patients feel unwell while taking levothyroxine monotherapy. The purpose of this task force was to review the goals of levothyroxine therapy, the optimal prescription of conventional levothyroxine therapy, the sources of dissatisfaction with levothyroxine therapy, the evidence on treatment alternatives, and the relevant knowledge gaps. We wished to determine whether there are sufficient new data generated by well-designed studies to provide reason to pursue such therapies and change the current standard of care. This document is intended to inform clinical decision-making on thyroid hormone replacement therapy; it is not a replacement for individualized clinical judgment.

METHODS

Task force members identified 24 questions relevant to the treatment of hypothyroidism. The clinical literature relating to each question was then reviewed. Clinical reviews were supplemented, when relevant, with related mechanistic and bench research literature reviews, performed by our team of translational scientists. Ethics reviews were provided, when relevant, by a bioethicist. The responses to questions were formatted, when possible, in the form of a formal clinical recommendation statement. When responses were not suitable for a formal clinical recommendation, a summary response statement without a formal clinical recommendation was developed. For clinical recommendations, the supporting evidence was appraised, and the strength of each clinical recommendation was assessed, using the American College of Physicians system. The final document was organized so that each topic is introduced with a question, followed by a formal clinical recommendation. Stakeholder input was received at a national meeting, with some subsequent refinement of the clinical questions addressed in the document. Consensus was achieved for all recommendations by the task force.

RESULTS

We reviewed the following therapeutic categories: (i) levothyroxine therapy, (ii) non-levothyroxine-based thyroid hormone therapies, and (iii) use of thyroid hormone analogs. The second category included thyroid extracts, synthetic combination therapy, triiodothyronine therapy, and compounded thyroid hormones.

CONCLUSIONS

We concluded that levothyroxine should remain the standard of care for treating hypothyroidism. We found no consistently strong evidence for the superiority of alternative preparations (e.g., levothyroxine-liothyronine combination therapy, or thyroid extract therapy, or others) over monotherapy with levothyroxine, in improving health outcomes. Some examples of future research needs include the development of superior biomarkers of euthyroidism to supplement thyrotropin measurements, mechanistic research on serum triiodothyronine levels (including effects of age and disease status, relationship with tissue concentrations, as well as potential therapeutic targeting), and long-term outcome clinical trials testing combination therapy or thyroid extracts (including subgroup effects). Additional research is also needed to develop thyroid hormone analogs with a favorable benefit to risk profile.

Thyroid hormone inactivation in gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are resistant to traditional chemotherapy but are responsive to the tyrosine kinase inhibitors imatinib and sunitinib. The use of these agents has improved the outcome for patients but is associated with adverse effects, including hypothyroidism. Multiple mechanisms of this effect have been proposed, including decreased iodine organification and glandular capillary regression. Here we report the finding of consumptive hypothyroidism caused by marked overexpression of the thyroid hormone-inactivating enzyme type 3 iodothyronine deiodinase (D3) within the tumor. Affected patients warrant increased monitoring and may require supernormal thyroid hormone supplementation.

Type 3 deiodinase: role in cancer growth, stemness, and metabolism

Deiodinases are selenoenzymes that catalyze thyroid hormones (THs) activation (type 1 and type 2, D1 and D2, respectively) or inactivation (type 3, D3). THs are essential for proper body development and cellular differentiation. Their intra- and extra-cellular concentrations are tightly regulated by deiodinases with a pre-receptorial control thus generating active or inactive form of THs. Changes in deiodinases expression are anatomically and temporally regulated and influence the downstream TH signaling. D3 overexpression is a feature of proliferative tissues such as embryo or cancer tissues. The enhanced TH degradation by D3 induces a local hypothyroidism, thus inhibiting THs transcriptional activity. Of note, overexpression of D3 is a feature of several highly proliferative cancers. In this paper, we review recent advances in the role of D3 in cancer growth, stemness, and metabolic phenotype. In particular, we focus on the main signaling pathways that result in the overexpression of D3 in cancer cells and are known to be relevant to cancer development, progression, and recurrence. We also discuss the potential role of D3 in cancer stem cells metabolic phenotype, an emerging topic in cancer research.

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

The major product secreted by the thyroid is thyroxine (T4), whereas most of the biologically active triiodothyronine (T3) derives from the peripheral conversion of T4 into T3. The deiodinase enzymes are involved in activation and inactivation of thyroid hormones (THs). Type 1 and type 2 deiodinase (D1 and D2) convert T4 into T3 whereas D3 degrades T4 and T3 into inactive metabolites and is thus the major physiological TH inactivator. The hypothalamic-pituitary-thyroid axis maintains circulating TH levels constant, while the deiodinases tissue-specifically regulate intracellular thyroid status by controlling TH action in a precise spatio-temporal fashion. Here we review the data related to the recent identification of a paraneoplastic syndrome called "consumptive hypothyroidism," which exemplifies how deiodinases alter substantially the concentration of TH in blood. This syndrome results from the aberrant uncontrolled expression of D3 that can induce a severe form of hypothyroidism by inactivating T4 and T3 in defined tumor tissue. This rare TH insufficiency generally affects patients in the first years of life, and has distinct features in terms of diagnosis, treatment, and prognosis with respect to other forms of hypothyroidism.

Hypothyroidism: etiology, diagnosis, and management

Hypothyroidism is the result of inadequate production of thyroid hormone or inadequate action of thyroid hormone in target tissues. Primary hypothyroidism is the principal manifestation of hypothyroidism, but other causes include central deficiency of thyrotropin-releasing hormone or thyroid-stimulating hormone (TSH), or consumptive hypothyroidism from excessive inactivation of thyroid hormone. Subclinical hypothyroidism is present when there is elevated TSH but a normal free thyroxine level. Treatment involves oral administration of exogenous synthetic thyroid hormone. This review presents an update on the etiology and types of hypothyroidism, including subclinical disease; drugs and thyroid function; and diagnosis and treatment of hypothyroidism.