DEFICIENCY

Severe deficiency of both iodine and selenium occurs in a region extending from north east China and nearby regions of Siberia and Korea to south west China, including Tibet.

Three disorders are associated with Se deficiency:

• Keshan disease
• Kashin-Beck disease
• Hypothyroid cretinism (in combination with iodine deficiency).

Keshan disease Definition

Named after Keshan county in NE China.
Keshan disease is a cardiomyopathy affecting mostly young and middle-aged women.
Symptoms:

• Multifocal myocardial necrosis and fibrosis, leading to
• cardiogenic shock and congestive heart failure.

The disease was shown by Chinese scientists in 1979 to be prevented by selenium supplementation.

Kashin-Beck disease Definition

The second disorder associated with selenium deficiency is Kashin-Beck disease, named after two investigators who studied affected patients in Siberia in the 19th century.

It is an osteoarthropathy of the hands and fingers, elbows, knees, and ankles in children and adolescents.

Characterized by necrosis of growth-plate and epiphyseal chondrocytes and proliferation of surrounding chondrocytes, it leads to a hypertrophic osteoarthropathy and, in some subjects, to short stature.

Effects of deficiency and excess:

Too little: reduced immune defences; muscle pain; muscular dystrophy; increased risk of cardiovascular disease if serum Se level is less than 50 µg/ml. (In Norway the average is 120 µg/ml.)

Too much: 2-3 mg/day for a prolonged period may bring about the early signs of toxicity: garlic smell of breath, hair loss, brittle nails, fatness, vomiting.