Anorexia nervosa is a state of self-induced starvation resulting in marked weight loss; bulimia is a condition in which the patient binges on food and then induces vomiting. Bulimia is more common than anorexia nervosa and carries a better prognosis. It is estimated to occur in 1% to 2% of women and 0.1% of men, with an average age at onset of 20 years. These disorders occur primarily in previously healthy young women who have acquired an obsession with attaining or maintaining thinness.
The clinical findings in anorexia nervosa generally are similar to those in SAM. In addition, effects on the endocrine system are prominent. Amenorrhea, resulting from decreased secretion of gonadotropin-releasing hormone (and consequent decreased secretion of luteinizing and follicle-stimulating hormones), is so common that its presence is almost a diagnostic feature. Other common findings, related to decreased thyroid hormone release, include cold intolerance, bradycardia, constipation, and changes in the skin and hair. In addition, dehydration and electrolyte abnormalities are frequent findings. Body hair may be increased but usually is fine and pale (lanugo). Bone density is decreased, most likely because of low estrogen levels, which mimics the postmenopausal acceleration of osteoporosis. As expected with severe malnutrition, anemia, lymphopenia, and hypoalbuminemia may be present. A major complication of anorexia nervosa is an increased susceptibility to cardiac arrhythmia and sudden death, both resulting from hypokalemia.
In bulimia, binge eating is the norm. Huge amounts of food, principally carbohydrates, are ingested, only to be followed by induced vomiting. Although menstrual irregularities are common, amenorrhea occurs in less than 50% of bulimic patients, probably because weight and gonadotropin levels are maintained near normal. The major medical complications are related to continual induced vomiting and chronic use of laxatives and diuretics. These include (1) electrolyte imbalances (hypokalemia), which predispose the patient to cardiac arrhythmias; (2) pulmonary aspiration of gastric contents; and (3) esophageal and stomach rupture. Nevertheless, there are no specific signs and symptoms for this syndrome, and the diagnosis must rely on a comprehensive psychologic assessment of the patient.
Before we summarize the functions of individual vitamins and the consequence of their deficiency, some general comments are in order.
Thirteen vitamins are necessary for health; four—A, D, E, and K—are fat-soluble and the remainder are water-soluble. The distinction between fatand water-soluble vitamins is important; although the former are more readily stored in the body, they may be poorly absorbed in fat malabsorption disorders, caused by disturbances of digestive functions (discussed in Chapter 15).
Certain vitamins can be synthesized endogenously—vitamin D from precursor steroids, vitamin K and biotin by the intestinal microflora, and niacin from tryptophan, an essential amino acid. Notwithstanding this endogenous synthesis, a dietary supply of all vitamins is essential for health.
Deficiency of a single vitamin is uncommon, and singleor multiple-vitamin deficiencies may accompany concurrent SAM.
In the following sections, vitamins A, D, and C are presented in some detail because of their wide-ranging functions and the morphologic changes of deficient states. This is followed by a summary in tabular form of the main consequences of deficiencies of the remaining vitamins—E, K, and the B complex—and some essential minerals.
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