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© Dirk Biddle
i) Iodine: The primary function of iodine (I) in the body is to provide a substrate for the synthesis of the thyroid hormones (thyroxine and triiodothyronine), which are crucial for normal growth and development.
Iodine deficiency results when iodide intake is less than 20 µg/day. In moderate iodine deficiency, the thyroid gland, under the influence of thyroid-stimulating hormone (THS), hypertrophies to concentrate iodide in itself, resulting in a colloid goiter. Most of these cases however remain euthyroid.
Severe iodine deficiency may result in endemic myxedema among adults and in endemic cretinism among infants. Several metabolic disturbances in thyroid hormone synthesis can cause both adult and infantile hypothyroidism. But worldwide, endemic iodine deficiency is still a major cause of hypothyroidism. Severe maternal iodine deficiency retards foetal growth and brain development. Endemic cretinism may occur in one of two forms (neurologic or myxedematous), depending on the interplay of iodine deficiency and genetics (1).
Today, one of the best ways to avoid iodide deficiency caused cretinism in infants and hypothyroidism in adults and toddlers is via iodised table salt. In western societies, the move toward “unadulterated” or “designer” salts has been accompanied by a worrying increase in rates of childhood cretinism and adult hyperthyroidism.
Iodine toxicity is more rare, and results when iodide intake is 20 times greater than the daily requirement, i.e., 2 mg/day. In some areas, particularly Japan, inhabitants consume as much as 50 to 80 mg/day, resulting in high plasma levels. Some of these persons develop goiters, but most remain euthyroid. Some develop myxedema, and some paradoxically develop hyperthyroidism (Jod-Basedow phenomenon). Increased uptake of iodine by the thyroid may lead to inhibition of thyroid hormone synthesis (Wolff-Chaikoff effect) and eventually causes iodide goiter or myxedema. At very high doses of iodide, a brassy taste, increased salivation, gastric irritation, and acneiform skin lesions may occur (1).
ii) Calcium is one of the most abundant and important minerals found in the human body. About 99 percent of the body's calcium is found in teeth and bones, and the rest circulates in the blood. Calcium is important for proper blood clotting, nerve, and cell activity. Calcium levels in the blood are controlled by the parathyroid glands and the kidneys. Blood calcium is used to monitor a range of conditions relating to bones, teeth, nerves, muscles, heart, and kidney.
About half of the body's calcium is bound by albumin. A low albumin level will cause the total calcium level in the blood to drop. Therefore, calcium values are interpreted in combination with albumin levels. An elevated calcium level can occur with bone and metabolic diseases, or be due to medications such as thiazide type diuretics, disorders of calcium handling in the kidneys, excess parathyroid gland activity, vitamin D deficiency and/or malabsorption of calcium from the intestines. Low calcium levels can be due to certain metabolic disorders such as insufficient parathyroid hormone, or drugs like Fosamax and furosemide type diuretics.
iii) Phosphorus is also largely stored in the bone. It is regulated by the kidneys, and high levels may be due to kidney disease. When low levels are seen with high calcium levels it suggests parathyroid disease, however there are other causes. A low phosphorus, in combination with a high calcium level, may suggest an overactive parathyroid gland.
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1 http://www.merck.com/mrkshared/mmanual/section1/chapter4/4c.jsp