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Thyrotropin-Secreting Pituitary Adenomas

ABSTRACT Thyrotropin-secreting pituitary tumors (TSH-omas) are a rare cause of hyperthyroidism and account for less than 1% of all pituitary adenomas. It is, however, noteworthy that the number of reported cases increased over the last few years because of the routine use of ultrasensitive immunometric assays for measuring TSH levels. Contrary to previous RIAs, ultrasensitive […]

Acute and Subacute, and Riedel’s Thyroiditis

ABSTRACT The thyroid, like any other structure, may be the seat of an acute or chronic suppurative or non-suppurative inflammation. Various systemic infiltrative disorders may leave their mark on the thyroid gland as well as elsewhere. Infectious thyroiditis is a rare condition, usually the result of bacterial invasion of the gland. Its signs are the […]

Thyroid Nodules and Thyroid Cancer Prior to, During, and Following Pregnancy

ABSTRACT Thyroid cancer is the second most common malignancy to co-occur in pregnancy. Further, the rising prevalence of treated thyroid cancer in women of child-bearing age means that survivors of thyroid cancer are frequently presenting for obstetric care, occasionally in the setting of persisting structural disease. To ensure that optimal health outcomes are achieved for […]

Thyroid Hormones in Brain Development and Function

ABSTRACT   Thyroid hormones are essential for normal brain development. They influence neurogenesis, neuronal and glial cell differentiation and migration, synaptogenesis, and myelination. Thyroid hormone deficiency may severely affect the brain during fetal and postnatal development, causing retarded maturation, intellectual deficits, and neurological impairment. Neural cells express the thyroid hormone nuclear receptors THRA and THRB, […]

Thyroid Nodules and Cancer in the Elderly

ABSTRACT   Thyroid nodules and thyroid cancer are common in elderly patients and demonstrate age-specific prevalence, malignancy risk, and clinical behavior. Improved risk stratification by ultrasound characteristics and molecular testing of thyroid nodules pre-operatively has reduced the need for diagnostic surgery in many individuals. In patients with differentiated thyroid cancer, total thyroidectomy and radioactive iodine […]

Clinical Strategies in the Testing of Thyroid Function

ABSTRACT   In the past decades, emphasis has shifted from testing thyroid function in individuals who are likely to have clinically overt thyroid disorders to a broader population, an approach that includes also identification of so-called subclinical or mild thyroid dysfunctions. The key measurement methods used to detect thyroid dysfunction are still serum thyroid stimulating […]

Ultrasonography of the Thyroid

ABSTRACT Thyroid ultrasonography (US) is the most common, extremely useful, safe, and cost-effective way to image the thyroid gland and its pathology. US has largely replaced the need for thyroid scintigraphy except to detect iodine-avid thyroid metastases after thyroidectomy and to identify hyper-functioning (toxic) thyroid nodules. This chapter reviews the literature; discusses the science and […]

Cellular Action of Thyroid Hormone

ABSTRACT Thyroid hormones (THs) regulate growth, development, metabolism. This chapter aims to provide a comprehensive overview of the molecular and cellular mechanism(s) for intracellular signaling by TH. At the cellular level, THs bind to thyroid hormone receptors (TRs) that are members of the nuclear hormone receptor family.  TRs act as ligand-activated transcription factors that bind […]

Hyperthyroidism in Aging

ABSTRACT   Hyperthyroidism in the elderly is a serious clinical condition that is associated with significant morbidity and excess mortality.  It may be difficult to diagnose due to the confounding effects of drugs and acute or chronic illnesses on the interpretation of thyroid function tests. Hyperthyroidism is usually diagnosed when a suppressed TSH level is […]

Graves’ Disease: Complications

ABSTRACT Thyroid storm is an acute and life-threatening worsening of hyperthyroidism, characterized by an exacerbation of symptoms and signs of hyperthyroidism, with high fever, dehydration, marked tachycardia or tachyarrhytmias, heart failure, hepatomegaly, respiratory distress, abdominal pain, delirium, possibly seizures. It may occur in patients submitted to thyroidectomy or radioactive iodine treatment while hyperthyroid, or as […]

The Iodine Deficiency Disorders

ABSTRACT This chapter provides an overview of the disorders caused by iodine deficiency. Extensively referenced, it includes data on dietary sources of iodine, goitrogens, the effects of iodine deficiency throughout the lifecycle, the pathophysiology of iodine deficiency, as well as strategies for control and monitoring of the iodine deficiency disorders, such as iodized salt and […]

Genetic Defects in Thyroid Hormone Supply

  ABSTRACT Congenital hypothyroidism (CH) is the most frequent endocrine-metabolic disease in infancy, with an incidence of about 1/2500 newborns [1, 2]. In the last 20-30 years the incidence of congenital hypothyroidism in newborns has increased from 1:4000 to 1:2000 [3, 4]. This phenomenon could be explained by using a lower b-TSH cutoff, that allowed […]

TSH Receptor Mutations and Diseases

ABSTRACT The thyroid-stimulating hormone (TSH) receptor (TSHR) is a member of the glycoprotein hormone receptors (GPHRs), a sub-group of class A G protein-coupled receptors (GPCRs). TSHR and its ligand thyrotropin are of essential importance for growth and function of the thyroid gland. The TSHR activates different G-protein subtypes and signaling pathways, of which Gs and […]

Hashimoto’s Thyroiditis

ABSTRACT Hashimoto’s thyroiditis is characterized clinically as a commonly occurring, painless, diffuse enlargement of the thyroid gland occurring predominantly in middle-aged women. The patients are often euthyroid, but hypothyroidism may develop. The thyroid parenchyma is diffusely replaced by a lymphocytic infiltrate and fibrotic reaction; frequently, lymphoid germinal follicles are visible. Persons with Hashimoto’s thyroiditis have […]

Disorders of the Thyroid Gland in Infancy, Childhood and Adolescence

This chapter is, in part, based on the previous version written by Prof. Rosalind Brown. ABSTRACT Thyroid disorders in infancy, childhood and adolescence represent common and usually treatable endocrine disorders. Thyroid hormones are essential for normal development and growth of many target tissues, including the brain and the skeleton. Thyroid hormone action on critical genes […]

Hypothyroidism in Older Adults

ABSTRACT Hypothyroidism is more common among elderly individuals due to the increasing incidence and prevalence of autoimmune thyroiditis that occurs with aging. Accurate diagnosis of this condition in the elderly may be challenging due to a number of factors including a relative paucity of referable symptoms, confounding findings that may be related to comorbid disorders, […]

Assay of Thyroid Hormones and Related Substances

 ABSTRACT This chapter reviews how improvements in sensitivity and specificity of thyroid function tests [total and free thyroid hormones, TSH, thyroid autoantibodies (TRAb, TPOAb and TgAb) and thyroglobulin (Tg)] have dramatically improved clinical strategies for detecting and treating thyroid disorders. The review discusses the strengths and limitations of the different methodologies currently used (RIA, IMA […]

Metabolism of Thyroid Hormone

    ABSTRACT Thyroid hormone is indispensable for normal development and metabolism of most cells and tissues. Thyroid hormones are metabolized by different pathways: glucuronidation, sulfation, and deiodination, the latter being the most important. Three enzymes catalyzing deiodination have been identified, called type 1 (D1), type 2 (D2) and type 3 (D3) iodothyronine deiodinases. D1 […]

Diagnosis and Treatment of Graves’ Disease

   ABSTRACT Diagnosis of the classic form of Graves’ disease is easy and depends on the recognition of the cardinal features of the disease and confirmation by tests such as TSH and FTI. The differential diagnosis includes other types of thyrotoxicosis, such as that occurring in a nodular gland, accompanying certain tumors of the thyroid, […]

Effects of the Environment, Chemicals and Drugs on Thyroid Function

ABSTRACT The sensitive and tightly regulated feedback control system, thyroid gland autoregulation, and the large intrathyroidal and extrathyroidal storage pools of thyroid hormone serve to provide a constant supply of thyroid hormone to peripheral tissues in the face of perturbations imposed by the external environment, chemicals and drugs, and a variety of diseases processes. The […]

Multinodular Goiter

ABSTRACT Multinodular goiter (MNG) is the most common of all the disorders of the thyroid gland. MNG is the result of the genetic heterogeneity of follicular cells and apparent acquisition of new cellular qualities that become inheritable. Nodular goiter is most often detected simply as a mass in the neck, but sometimes an enlarging gland […]

PHYSIOLOGY OF THE HYPOTHALAMIC-PITUITARY-THYROID AXIS

ABSTRACT    The activity of the thyroid gland is predominantly regulated by the concentration of the pituitary glycoprotein hormone, thyroid-stimulating hormone (TSH). In the absence of pituitary or of thyrotroph function hypothyroidism ensues. Thus, regulation of thyroid function in normal individuals is to a large extent determined by the factors which regulate the synthesis and secretion […]

Thyroid Regulation and Dysfunction in the Pregnant Patient

ABSTRACT Thyroid disease in pregnancy is a common clinical problem. During the past 2 years significant clinical and scientific advances have occurred in the field. This chapter reviews the physiology of thyroid and pregnancy focusing on iodine requirements and advances in placental function. There follows discussion on thyroid function tests in pregnancy and their interpretation […]

Thyroid Nodules

ABSTRACT Thyroid cancer accounts for only 0.4% of all cancer deaths, with an incidence of 11 cases and about 0.5-0.6 deaths per 100,000 population in the United States each year,according to the November 2011 SEER report (http://seer.cancer.gov/statfacts/html/thyro.html). Its clinical importance, by contrast, is out of all proportion to its incidence, because cancers of the thyroid […]

Cellular Uptake of Thyroid Hormones

ABSTRACT The biological activity of thyroid hormone (TH) is regulated at the target tissue level by two important processes, i.e. deiodination and plasma membrane transport. The first process involves the expression of the deiodinase D2, which converts the prohormone T4 to bioactive T3, and/or of the deiodinase D3 which converts both T4 and T3 to […]