Physical symptoms include rapid loss of weight, unusual appetite, rapid pulse, diarrhea, and muscle weakness (especially in the legs, as when climbing stairs). The classical symptoms of hyperthyroidism are staring eyes and enlargement of the neck, but these need not be present. It is interesting to note that certain factors in upbringing and personality seem to predispose people to hyperthyroidism (this would mean that a feedback loop of the second type may precipitate the disease in some people). Individuals who later develop hyperthyroidism often have these characteristics: {103} * They were forced prematurely to become self-sufficient and responsible. * They felt rejected by one or both parents and feared a loss of emotional support. * Their early dependence needs (their needs for affection, mothering, warmth, etc.) were frustrated, and this led to feelings of insecurity and low self-esteem and to the belief that the world is a threatening place. * They often had dominant, tight-lipped, overcontrolling mothers. HYPOTHYROIDISM An underactive thyroid, known as _hypothyroidism_, is caused by an inadequate production of thyroid hormone. It is most common in middle-aged women. The emotional symptoms of hypothyroidism include mental sluggishness, nervousness, depression, irritability, impatience, and frequently dislike of everyday activities. Physical symptoms include a sense of heaviness and lethargy, dry skin, sensitivity to cold, constipation, and thinning hair. HYPER- AND HYPOPARATHYROIDISM The parathyroid glands, which are four bean-size glands located on top of the thyroid gland, manufacture hormones that regulate phosphorus and calcium levels in the body. Excess hormone raises the calcium level too high, and psychotic-like behavior can result. Too little hormone lowers the calcium level to the point that a person may behave like an alcoholic. These conditions are comparatively rare. DIABETES Diabetes, or hypoinsulism, which at the time of this writing affects as many as 2.5 million Americans, results from underproduction of insulin, which in turn causes an excess of sugar in the blood and urine. Diabetes takes two forms: juvenile onset (or insulin-dependent) and adult onset (or noninsulin-dependent) diabetes. The first type starts in childhood or young adulthood, and is caused by the body's failure to produce enough insulin. Juvenile onset diabetes is {104} usually controlled by means of regular injections of insulin.