Iodine deficiency
Iodine deficiency: Excerpt from Professional Guide to Diseases (Eighth Edition)
Iodine deficiency is the absence of sufficient levels of iodine to satisfy daily metabolic requirements. Because the thyroid gland uses most of the body’s iodine stores, iodine deficiency is apt to cause hypothyroidism and thyroid gland hypertrophy (endemic goiter). Other effects of deficiency range from dental caries to cretinism in neonates born to iodine-deficient mothers. Iodine deficiency is most common in pregnant or lactating women due to their exaggerated metabolic need for this element. Iodine deficiency responds readily to treatment with iodine supplements.
Causes
Iodine deficiency usually results from insufficient intake of dietary sources of iodine, such as iodized table salt, seafood, and dark green, leafy vegetables. (Normal iodine requirements range from 35 mcg/day for infants to 150 mcg/day for lactating women; the average adult needs 1 mcg/kg of body weight.) Iodine deficiency may also result from an increase in metabolic demands during pregnancy, lactation, and adolescence.
Signs and symptoms
Clinical features of iodine deficiency depend on the degree of hypothyroidism that develops (in addition to the development of a goiter). Mild deficiency may produce only mild, nonspecific symptoms, such as lassitude, fatigue, and loss of motivation. Severe deficiency usually generates the typically overt and unmistakable features of hypothyroidism: bradycardia; decreased pulse pressure and cardiac output; weakness; hoarseness; dry, flaky, inelastic skin; puffy face; thick tongue; delayed relaxation phase in deep tendon reflexes; poor memory; hearing loss; chills; anorexia; and nystagmus. In women, iodine deficiency may also cause menorrhagia and amenorrhea.
Cretinism — hypothyroidism that develops in utero or in early infancy — is characterized by failure to thrive, neonatal jaundice, and hypothermia. By age 3 to 6 months, the infant may display spastic diplegia and signs and symptoms similar to those seen in infants with Down syndrome.
Diagnosis
Confirming diagnosis Abnormal laboratory test results include low thyroxine (T4) levels with high radioactive iodine (131I) uptake, low 24-hour urine iodine levels, and high thyroid-stimulating hormone levels. Radioiodine uptake test traces 131I in the thyroid 24 hours after administration; triiodothyronine-resin or T4-resin uptake test shows values 25% below normal.
Treatment
Severe iodine deficiency requires administration of iodine supplements (potassium iodide [SSKI]). Mild deficiency may be corrected by increasing iodine intake through the use of iodized table salt and consumption of iodine-rich foods (seafood and green, leafy vegetables).
Special considerations
❑ Administer SSKI preparation in milk or juice to reduce gastric irritation and mask its metallic taste. To prevent tooth discoloration, tell the patient to drink the solution through a straw. Store the solution in a light-resistant container.
❑ To prevent iodine deficiency, recommend the use of iodized salt and consumption of iodine-rich foods for high-risk patients — especially adolescents and pregnant or lactating women.
❑ Advise pregnant women that severe iodine deficiency may produce cretinism in neonates, and instruct them to watch for early signs of iodine deficiency, such as fatigue, lassitude, weakness, and decreased mental function.
Book Source Details
- Book Title: Professional Guide to Diseases (Eighth Edition)
- Author(s): Springhouse
- Year of Publication: 2005
- Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2005 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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