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Adrenal cortex

Abstract Background The adrenal cortex produces three types of steroid hormones: mineralocorticoids, which regulate sodium and water balance; glucocorticoids, which stimulate glucose production and suppress immune function; and adrenal androgens, which influence sexual differentiation. All three types of adrenocortical steroids are synthesized from cholesterol, but regulation of production and secretion of the hormones involves several biosignaling mechanisms, some of which are unique to a particular hormone,…

Pituitary function and pathophysiology

Abstract Background The anterior and posterior lobes of the pituitary gland control processes vital for survival of the individual and the species. Although growth in infancy and childhood depend on nutrition, genetics, and environment, thyroid hormone and growth hormone (GH) are essential contributors to growth. Thyroid hormone is a master regulator of the metabolic rate and neurologic development in utero, in infancy, and in childhood. The…

Bone and mineral metabolism

Abstract Background The skeletal system is one of the largest organs in the body and is one of the hallmarks that distinguishes vertebrates from invertebrates. It is the storehouse for 98 to 99% of the body’s 1 kg of calcium. Bones are mineralized connective tissue in which type I collagen forms a network of flexible fibers. Mineralization of this network, or matrix, with calcium salts is…

Monoamine-producing tumors

Abstract Background Monoamine-producing tumors include neuroblastomas, pheochromocytomas, paragangliomas, and gastroenteropancreatic neuroendocrine tumors (GEP-NETs). Synthesis, storage, and secretion of biogenic amines and polypeptide hormones are characteristics of these tumors that both underlie their clinical manifestations and provide a means for laboratory diagnosis. The clinical features and related patterns and types of hormones produced by the tumors are highly heterogeneous and no single biomarker can reliably diagnose any…

Gastric, intestinal, and pancreatic function

Abstract Background The stomach, intestinal tract, and pancreas are closely related both anatomically and functionally. The clinical manifestations, such as diarrhea or malabsorption, may be associated with disease of any of these organs. It is therefore appropriate to discuss them together. Advances in imaging techniques and improvements in endoscopic procedures have led to many traditional laboratory tests of gastrointestinal (GI) and pancreatic function becoming obsolete. However,…

Liver disease

Abstract Background The liver is the largest and most complex organ in the body. The anatomy of the liver is intricate, and its function is dependent on the close interaction of resident cell lineages; the arterial, venous, and portal vasculature; and the biliary system. The liver plays a central role in numerous biochemical processes, executing metabolic and catabolic functions that are vital for homeostasis and health.…

Disorders of water, electrolytes, and acid-base metabolism

Abstract Background A complex yet elegant system of chemical buffers together with highly specialized mechanisms of the lungs and kidneys continuously work in tandem to ensure a precise balance of water, electrolytes, and pH in both the intracellular and extracellular compartments of the human body. Although these systems display impressive resilience and responsiveness to perturbation by illness or injury, they do have limits, at which point…

Kidney disease

Abstract Background The kidneys play a central role in homeostasis, and reduced renal function strongly correlates with increasing morbidity and mortality. Laboratory investigations are central to the diagnosis and management of kidney disease and investigations of kidney function constitute a significant element of the workload of most clinical laboratories. Content This chapter describes the basic anatomy and physiology of the kidneys as a foundation for understanding…

Cardiac function

Abstract Background Increases in cardiac biomarkers of myocardial injury and particularly cardiac troponin (cTn), in the absence of analytical confounders, define the presence of myocardial injury which in the proper clinical situation can lead to the diagnosis of acute myocardial infarction (AMI). Other biomarkers such as natriuretic peptides (NPs) facilitate the diagnosis and/or exclusion of heart failure (HF). These and other important biomarkers improve patient management…

Diabetes mellitus

Abstract Background Diabetes mellitus is a common disorder in which patients develop hyperglycemia due to inadequate insulin secretion, defective insulin action, or both. There are two major forms of diabetes, namely type 1 and type 2. The estimated global prevalence of diabetes in adults is ~460 million. Many patients with diabetes develop severe debilitating complications, including blindness, renal failure, peripheral vascular disease, myocardial infarction, and stroke.…

Nutrition: Laboratory and clinical aspects

Abstract Background Nutrition is relevant to every specialty within overall medical practice. Adequate nutrition, both qualitatively and quantitatively, is essential for normal development, growth, function, and health. Both excessive and insufficient intake of individual nutrients can have adverse consequences. Also, patients with many pathologic conditions who have free access to a good diet may benefit from nutritional supplementation or restriction. Content This chapter describes all the…

Body fluids

Abstract Background Body fluids are collected and analyzed either to gain insight into the processes that contribute to the accumulation of that fluid within a body compartment or to provide diagnostic information to investigate pathophysiologic processes. Content In the preanalytical phase, the route, equipment, and mechanism for obtaining and transporting the body fluid specimen (including required collection device, volume, temperature, and timeliness of transport to the…

Toxic elements

Abstract Background Elements have been recognized as toxins for centuries. Many elements are essential for life but if an individual’s exposure exceeds a certain threshold, toxicity may develop. When identified early, disease caused by elemental exposure is readily treatable with good outcomes. Conversely, if exposure is not identified and reduced, serious and sometimes irreparable damage to the nervous, renal, and cardiovascular systems can occur. The laboratory…

Clinical toxicology

Abstract Background Toxicology is a broad, multidisciplinary science where the goal is to determine the effects of chemical agents on living systems. Innumerable potential toxins can inflict harm, including pharmaceuticals, herbals, household products, environmental agents, occupational chemicals, drugs of abuse, and chemical terrorism threats. Each year millions of human exposure cases are reported worldwide. The Centers for Disease Control and Prevention (CDC) has reported that poisoning…

Therapeutic drugs and their management

Abstract Background Therapeutic drug monitoring (TDM) is the traditional term used for the activity of measuring drug concentrations to tailor the dose of the medication to an individual. The use of monitored drug therapy is generally reserved for drugs with a narrow therapeutic index (TI), with variable pharmacokinetic behavior, and for which the efficacy or toxicity is difficult to measure or detect early during therapy. Content…

Porphyrins and the porphyrias

Abstract Background The porphyrias are a group of rare, mainly inherited metabolic disorders that result from decreased or, in one rare form of erythropoietic protoporphyria, increased, activities of the enzymes of heme biosynthesis. Each porphyria is defined by the association of characteristic clinical features with a specific pattern of heme precursor accumulation that reflect the buildup of substrates upstream of the enzyme that is partially deficient,…

Iron metabolism

Abstract Background Iron plays an essential role in many biochemical processes, in particular in the production of heme for incorporation in hemoglobin and iron-sulfur clusters, which serve as enzyme cofactors. Measurement of iron and other indicators of body iron are helpful in the assessment of some of the world’s most prevalent disorders: iron deficiency, iron overload, and iron distribution disorders. Content This chapter describes the processes…

Vitamins and trace elements

Abstract Background An adequate supply of vitamins and trace elements is critical in maintaining optimum health. Measurements of vitamin and trace element concentrations are frequently helpful in nutritional assessment and may be a requisite in suspected deficiency or toxicity, and in the management of patients with cystic fibrosis (CF), bariatric surgery, and for those on nutritional support in the intensive or critical care units. There is…

Hormones

Abstract Background Hormones are a diverse group of compounds that circulate in body fluids at very low and variable concentrations. Hormones perform important signaling and communication roles between cells and tissues of the body. Accurate measurement of hormone concentrations in patient samples is critical for accurate clinical diagnosis of acute illness and chronic disease. Content Endocrine hormones are chemical messengers that communicate between cells and tissues.…

Electrolytes and blood gases

Abstract Background Electrolyte balance within the human body is essential for maintenance of health. Dysregulation of electrolytes affects water homeostasis and acid-base status and often results in overt clinical signs and symptoms. The laboratory is tasked with aiding the clinician by providing accurate, timely results to narrow or confirm a diagnosis. In challenging cases in which the clinical context is lacking or conflicting, it is even…