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Polyglandular Disorders

Definition Polyglandular syndromes are disorders of dysfunction and pathology of more than one endocrine gland. These disorders can be classified into neoplastic syndromes with abnormal endocrine cell proliferation and often, but not invariably, hormone hypersecretion, and autoimmune syndromes , in which immune destruction of endocrine cells often results in hypofunction and reduced hormone secretion. Both the neoplastic and autoimmune polyglandular syndromes often have nonendocrine manifestations that…

Hypoglycemia

Definition Hypoglycemia is a common biochemical abnormality observed in clinical practice. Hypoglycemic disorders are more frequent in neonates, infants, and children than adults. Delay in diagnosis and inappropriately treated hypoglycemia can have severe consequences, including seizures, permanent brain injury, or death. In adults, no single plasma glucose concentration categorically defines hypoglycemia. Rather, clinical hypoglycemia is defined as a plasma (or serum) glucose concentration low enough to…

Diabetes Mellitus

Overview Diabetes mellitus is a chronic metabolic disorder characterized by raised glucose concentrations and associated alterations in the metabolism of fat, protein, and carbohydrates. Chronically elevated blood glucose levels increase the risk of developing macrovascular and microvascular complications. Diabetes comprises a cluster of heterogeneous disorders with elevated blood glucose concentrations, but the cluster includes many subcategories, each of which requires tailored prevention, diagnosis, and treatment approaches.…

Adrenal Medulla, Catecholamines, and Pheochromocytoma

Adrenal Medulla and Catecholamines The adrenal medulla occupies the central portion of the adrenal gland. Adrenomedullary cells are called chromaffin cells because they stain brown with chromium salts. Chromaffin cells differentiate in the center of the adrenal gland in response to cortisol; some chromaffin cells also migrate to form paraganglia. The largest cluster of chromaffin cells outside the adrenal medulla is near the level of the…

Adrenal Cortex

Normal Anatomy and Function The adrenal glands weigh 6 to 8 g in adults ( Fig. 208-1 ). Each contains a cortex, which makes steroid hormones, and a medulla, which produces catecholamines. Diseases of the adrenal medulla are discussed in Chapter 209 . In the adrenal cortex, production of the three major classes of steroids occurs in specific zones: (1) the outermost layer, which is the glomerulosa,…

Thyroid

Overview of Thyroid Disease The thyroid gland synthesizes both T 4 and T 3 , which are essential for normal human growth and development and for normal physiologic function during adult life. Thyroid hormone levels are genetically set in each individual and are regulated by a negative feedback loop that allows for exquisite control. Disorders of thyroid hormone production, including both hypothyroidism and hyperthyroidism, have diverse…

Posterior Pituitary

Anatomy and Hormone Synthesis Vasopressin and oxytocin, which are hormones of the posterior pituitary, are synthesized in specialized neurons of the hypothalmus. These neurons, notable for their large size, are termed magnocellular neurons . In the hypothalamus, the magnocellular neurons are clustered in the paired paraventricular and supraoptic nuclei ( Fig. 206-1 ). Vasopressin and oxytocin are also synthesized in parvocellular (i.e., small cell) neurons of…

Anterior Pituitary

Definition The pituitary is located in the sella turcica, which is a part of the sphenoid bone of the skull. It is attached to the base of the brain by a stalk, known as the infundibulum, and is contained in a capsule that is continuous with the dura mater, thereby placing it technically outside of the blood-brain barrier. The gland itself is composed of two parts,…

Neuroendocrinology and the Neuroendocrine System

Neuroendocrine Regulation Neuroendocrinology is the interactions between the nervous system and the endocrine system’s metabolic and hormonal homeostatic activities. One role the nervous system has is to connect the environment with the body. The most important environmental factors are temperature and light, which fluctuate in a predictable way each day. Humans have a circadian clock ( Chapter 374 ) to assure that physiology and behavior are…

Principles of Endocrinology

The principal manifestation of most endocrine diseases is over- or undersecretion of one or more hormones, but the causes of endocrine disease are not unique to endocrinology as a subspecialty of medicine. Major causes of endocrine disease that are shared with diseases of other organ systems include benign or malignant proliferation of endocrine cells; destruction of endocrine cells by autoimmune, infectious, or other infiltrative processes; mutations…

Approach to the Patient with Endocrine Disease

Most endocrine disorders are due to either an excess or a deficiency of a hormone that is transported in the systemic circulation and therefore result in multiorgan manifestations. Since individual hormones commonly have multiple sites of action, patients rarely present with a single set of symptoms or signs isolated to only one organ system. Generalized nonspecific symptoms such as weakness, difficulty concentrating, lack of energy, and…

Obesity

Obesity is the most common nutritional disorder in the United States, and it directly or indirectly accounts for a significant portion of health-related expenses. Lifestyle change, antiobesity medications, and bariatric surgery are evidence-based treatment options, but each requires training and time to implement. Definition Obesity, which is a degree of excess adiposity that can predispose to adverse health consequences, is a disease of body weight regulation,…

Eating Disorders

Definition Feeding and eating disorders are characterized by a persistent disturbance of eating or eating-related behavior that results in the altered consumption or absorption of food and that significantly impairs physical health or psychosocial functioning. The Diagnostic and Statistical Manual of Mental Disorders , 5th edition (DSM-5) provides formal criteria defining anorexia nervosa, bulimia nervosa, binge-eating disorder, and avoidant/restrictive food intake disorder. Presentations that do not…

Vitamins, Trace Minerals, and Other Micronutrients

Micronutrients in Nutritional Science Dietary Requirements Micronutrients are a diverse array of dietary components that are necessary to sustain health. The physiologic roles of micronutrients are as varied as their composition. Some micronutrients are used in enzymes as either coenzymes or prosthetic groups, some are biochemical substrates or hormones; in some instances, functions are not well defined. Under normal circumstances, the average daily dietary intake required…

Iron Overload (Hemochromatosis)

Definition Hereditary hemochromatosis is an inherited disorder that leads to iron overload due to excessive absorption of dietary iron because of a deficiency of hepcidin, which is an iron regulatory peptide hormone. A homozygous C282Y mutation in HFE is responsible for the vast majority of hereditary cases. However, iron overload due to hyperabsorption of dietary iron may result from other genetic mutations, chronic anemias associated with…

Wilson Disease

Definition Wilson disease is an autosomal recessive disorder of copper transport. Affected individuals accumulate toxic levels of copper in the liver and later in the brain as a consequence of mutations in both alleles of the Wilson disease gene ( ATP7B ). The gene encodes a copper-transporting ATPase expressed primarily in hepatocytes in the liver, where its major function is excretion of hepatic copper into the…

The Porphyrias

Definition The porphyrias, which are a group of disorders that arise from disturbances in heme synthesis, are characterized by the accumulation of porphyrins or their precursors on the heme biosynthetic pathway. Most porphyrias are genetic and heritable, except for the sporadic form of porphyria cutanea tarda and rare instances of porphyria arising from acquired somatic mutations. Approximately 90% of heme biosynthesis occurs within the erythron, where…

Homocystinuria and Hyperhomocysteinemia

Definition Homocysteine, which is a nonprotein amino acid, is a key metabolic branch point metabolite between the trans-sulfuration and remethylation pathways of methionine metabolism. The many conditions associated with high homocysteine levels encompass a wide range of clinical manifestations. The normal level of plasma total homocysteine is below 15 µM. However, the threshold of total homocysteine above which a disorder of homocysteine metabolism should be suspected…