Anorexia Nervosa 343
Hematology. Leukopenia is common, with the loss of all cell types but usually with ap-
parent lymphocytosis. Mild anemia can occur,  as well as thrombocytopenia and, rarely,
bleeding problems. 
Serum chemistry. Dehydration may be reflected by an elevated blood urea nitrogen
level. Hypercholesterolemia is common. Hepa tic enzyme levels may be elevated. Hypo-
magnesemia, hypozincemia, hypophosphatemia, and hyperamylasemia are occasionally
observed. Self-induced vomiting may lead to metabolic alkalosis (elevated serum bicarbon-
ate), hypochloremia, and hypokalemia; laxative  abuse may cause a mild metabolic acidosis. 
Endocrine. Serum thyroxine (T4) levels are usually in the low-normal rang e; triiodothy-
ronine (T3) levels are decreased, while reverse T3 levels are elevated. Females have low se-
rum estrogen levels, whereas males have  low levels of se rum testosterone.
Electrocardiography. Sinus bradycardia is common, and,  rarely, arrhythmias are noted.
Significant prolongation of the QTc interv al is observed in some individuals. 
Bone mass. Low bone mineral density, with specific areas of osteopenia or osteoporo-
sis, is often seen. The risk of fr acture is significantly elevated.
Electroencephalography. Diffuse abnormalities, reflecting a metabolic encephalopa-
thy, may result from significant fluid and electrolyte disturbances. 
Resting energy expenditure. There is often a significant redu ction in resting energy ex-
penditure.